Controversies in Clear Aligner Therapy Contemporary Perspectives

Controversies
in Clear Aligner
Therapy
Contemporary Perspectives,
Limitations, and Solutions
Anderson T. Huang
Darren Huang
123
Controversies in Clear Aligner Therapy
Anderson T. Huang • Darren Huang
Controversies in Clear
Aligner Therapy
Contemporary Perspectives,
Limitations, and Solutions
Anderson T. Huang Darren Huang
Department of Orthodontics Department of Orthodontics
New York University, College of New York University, College of
Dentistry Dentistry
New York, NY, USA New York, NY, USA
ISBN 978-3-030-92809-4 ISBN 978-3-030-92810-0 (eBook)

https://doi.org/10.1007/978-3-030-92810-0
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature
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For Johnny
Foreword
Authoring an orthodontic textbook to address controversies is refreshing,

ambitious, and evidence of self-reflection by the authors who have gained a
good amount of experience with clear aligners. In the age of evidence-based
practice in health care, this was a much-needed effort to examine critically, 22
years after the launch of Invisalign, the current knowledge regarding the
treatment of malocclusions with clear aligners.
As Chair of the Department at New York University where Drs. Anderson
and Darren Huang teach orthodontics, I am honored to write the Foreword to
their book, Controversies in Clear Aligner Therapy: Contemporary
Perspectives, Limitations, and Solutions. They are both graduates of the
College of Dentistry and of the Advanced Education programs. Dr. Anderson
Huang’s long interest in clear aligner therapy has been well known in the
Department of Orthodontics for many years. He is joined by his son Darren,
a more recent graduate, who shares the same clinical interest and educational
perspectives. As orthodontists, neither one is inclined to settle for less than
excellence.
One of my goals as Chair of the Department of Orthodontics is to educate
students to consider the best interest of the patients they care for, and there-
fore to adopt a best-practice approach to treatment planning. With this in
mind, there is a dearth of books devoted to clear aligners other than those
which explain how to use the appliances and how to plan and sequence tooth
movements with the aligners. As a practitioner, I find such information much
needed, and I believe that sharing one’s experience on any treatment modality
with one’s orthodontist peers is valuable and respectable. Like many, I was at
first a dubious user of clear aligners for orthodontic treatment. Some move-
ments, such as extrusion or rotations, were difficult to accomplish and fre-
quently required fixed appliances to achieve treatment goals to satisfaction.
It is undeniable that 20 years later, orthodontic treatment with clear align-
ers has become more sophisticated; for example, the software platforms have
made communication with technicians easier. With software improvements,
practitioners have learned to plan tooth movement better, and this brought
their treatment goals and planning to higher grounds. However, despite these
improvements, there are still many global questions practitioners have regard-
ing this treatment modality no matter the type of aligner one may prefer or
select.
What sets this work apart is the authors’ reflections and their acknowl-
edgement that there are debate and disagreements on the effectiveness of
vii
viii Foreword
clear aligners. To name a few: their use during interceptive treatment, as sub-
stitute to functional appliances, the predictability of root movements, is there
too much interproximal enamel reduction being used, or excessive expansion
prescribed. Additionally, how effectively can one correct an open bite with
clear aligners, when many have been humbled by attempting bite closure
with mere fixed appliances.
Such reflective work is welcome by all orthodontists interested in using
clear aligners on a routine basis. After all, it took many years of practice and
learning from mistakes to master the use of fixed appliances whether on the
labial or lingual side of the dental arches. For those who first thought that
clear aligners would be the panacea of orthodontic treatment, one just needs
to recall the enthusiasm generated by the wide accessibility to straight-wire
appliances and the belief that orthodontic treatment could be rendered by any
practitioner no matter their degree of knowledge or experience.
I think you will find this book very useful and refreshing to read; you are
not the only one to have questions, strong convictions, and doubts, and yet
wish to better yourself in treating patients with clear aligners because you
understand that they are here to stay.
I applaud Drs. Anderson and Darren Huang for researching and writing
this book, for being thorough in their thinking, and for demonstrating critical
judgment on the efficacy of treatment with clear aligners. With these efforts,
we are all going to improve our treatment of patients with clear aligners.
Olivier Nicolay
Chair, Department of Orthodontics
New York University
New York, NY, USA
August 30, 2021
Preface
Since the introduction of the Invisalign appliance in 1999, clear aligner ther-
apy has gradually become a significant modality of orthodontic treatment for
the modern orthodontist and an area of intensive scientific research in the
orthodontic field. The first clear aligners were limited to the treatment of mild
malocclusions in adult patients. In the last 20 years, technological develop-
ments in clear aligner software, improvements in aligner materials and their
functionality, and innovations in treatment methods have expanded the capa-
bilities of clear aligner therapy for the treatment of complex malocclusions in
children, adolescents, and adults. Clear aligner therapy is rapidly evolving
and represents one of the next frontiers for orthodontic treatment.
Despite these advances, clear aligner therapy remains limited by signifi-
cant deficiencies resulting in clinical dilemmas for the practitioner, from the
use of clear aligners for interceptive treatment, complex movements, Class II
therapy, overcorrection, to the treatment of vertical problems. With the rapid
growth of clear aligner therapy within the field, there has arisen a dense forest
of contradictory and controversial opinions and methodologies for treatment.
Our own experience with clear aligner therapy has been a humbling but
enlightening process, one in which we have had to negotiate the appliance’s
limitations over the course of its evolution. Additionally, aside from a limited
number of systematic reviews and meta-analyses, there are few texts that
deeply engage with the limitations of clear aligner therapy and their implica-
tions. Therefore, there exists a need for a critical appraisal of the current body
of knowledge to determine viable treatment approaches in addressing these
dilemmas.
To address this need, we do not intend this book to be an exhaustive survey
of clear aligner therapy or a stepwise guide with generalized formulas for the
management of malocclusions with clear aligners. Instead, our aim is to pro-
vide rigorous, scientific evidence-based evaluations of the current status of
knowledge regarding controversial dilemmas within clear aligner therapy,
while mapping out solutions for their management. Each chapter will focus
on a dilemma, which we have frequently encountered in clinical practice and
the scientific literature. We will comprehensively analyze each dilemma with
a discussion of the current state of affairs in the context of the latest research,
its clinical implications including the limitations the dilemma bears on the
treatment of specific malocclusions, and our strategies for solutions. As learn-
ing tools, we have included numerous cases for study with their virtual set-
ups. Additionally, we have incorporated a series of prototypes, figures
ix
x Preface
illustrating suggested technological modifications, and future clinical appli-

cations with clear aligners.
Because we aim to be as impartial and comprehensive as possible in our
evaluations of these dilemmas, we have included discussions of clear aligner
systems alternative to Invisalign. However, this is not always possible because
certain aspects of clear aligner therapy with the Invisalign system are cur-
rently significantly advanced and not yet available in the alternative systems,
such as a developed bite jump function or optimized attachments. Nevertheless,
we believe these alternative systems, in addition to clinician-printed aligners
(via in-office 3D printers), will become increasingly viable for the treatment
of both simple and complex malocclusions.
This book seeks to address the ambiguity and confusion surrounding the
most pressing and troubling clinical dilemmas in clear aligner therapy. It
intends to provide the clinician greater clarity and understanding on these
dilemmas, as well as paradigms for their resolution. We hope this book can
serve as a valuable contribution to the discussion surrounding these topics
and that it will assist readers in making more informed and effective clinical
decisions in their delivery of clear aligner treatments.
New York, NY Anderson Huang

New York, NY Darren Huang
Acknowledgments
We are deeply grateful to Dr. Olivier Nicolay, Dr. Jae Hyun Park, and Dr.
George Anastassov, who believed in this project from the very start and
offered their early support and invaluable guidance. We sincerely thank
Springer Nature and our generous and perceptive editors, Alison Wolf,
Priyadarshini Vasudevan, and Shilpa Sheetal, for graciously offering us the
opportunity to realize our project and patiently directing us from proposal to
publication.
We thank the New York University College of Dentistry Department of
Orthodontics for their commitment to an evidence-based best-practice
approach to orthodontic practice, their continued innovations in clear aligner
research and therapy, and for creating space for us to nurture our ideas for
optimal patient care.
We thank Dr. Mitchell J. Lipp for his insight, friendship, and support.
We would like to express our love and gratitude for our family, Jennifer
and Madeline, for their patience, enthusiasm, and support, throughout this
entire project.
xi
Contents
1 Optimizing Diagnosis and Treatment Planning

with Clear Aligner Software�� 1
Clear Aligner Software: A Brief History �� 1
Major Deficiencies in the Invisalign Clincheck Software�� 2
Single Tooth Movement: Incompatibilities in Attachment
Design�� 2
Single Tooth Movement: Limitations in Torque Application�� 5
Single Tooth Movement: Limitations during Extraction
Therapy�� 8
Deficiencies in Hard and Soft Tissue Modeling�� 9
Limitations in the Correction of Skeletal Discrepancies �� 9
Limitations in Diagnostic Tools�� 10
The 3M Software �� 11
Optimizing Single Tooth Movement: Capabilities
and Limitations of Attachment Design�� 11
Optimizing Single Tooth Movement: Torque Application
and Bite Opening �� 12
Hard and Soft Tissue Modeling �� 13
Limitations in the Treatment of Complex Malocclusions�� 14
Dentsply Sirona Suresmile Software �� 14
Optimizing Single Tooth Movement: Attachment Design�� 14
and Bite Ramps�� 15
Treatment of Complex Malocclusions �� 16
uLab Software�� 16
Optimizing Single Tooth Movement: Attachment Design�� 16
and Bite Ramps�� 18
The Ideal Clear Aligner Software�� 19
Optimizing Tooth Movement: Attachment Design�� 19
Optimizing Tooth Movement: Torque Application�� 20
xiii
xiv Contents

3D Printer Compatibility�� 21
References�� 21
2 Adapting Clear Aligner Therapy to Interceptive Treatment
for Early Mixed Dentitions: Are They the Same as Late
Teen or Adult Treatment? �� 23
Clear Aligner Therapy for Interceptive Treatment: Challenges
and Considerations�� 23
Major Features of Clear Aligner Interceptive Treatment �� 24
Expansion�� 24
Eruption Compensation �� 25
Optimized Attachments�� 25
Mandibular Advancement�� 26
Phase II Treatment �� 26
Frequent Midcourse Corrections�� 27
Duration of Aligner Wear�� 27
Treatment Applications�� 27
The Deficiencies of Interceptive Treatment with Clear Aligners�� 34
Limitations in Growth Modification and Prediction�� 34
Range of Expansion �� 34
Adaptation to Short Clinical Crowns �� 34
Software Calibration for Treatment Planning�� 36
Availability of Clinical Preferences �� 36
Post-Interceptive Treatment Retention�� 40
Solutions to Current Limitations in Clear Aligner Interceptive
Treatment �� 40
Incorporating Orthopedic Appliances�� 40
Retention to Small Clinical Crowns�� 47
Expansion Limits �� 48
Software Calibration for Eruption Compensation
and Incisor Position�� 48
Expanding Clinical Preferences�� 48
Post-Interceptive Treatment Retention�� 49
The Viability of Interceptive Treatment with Clear Aligners�� 50
References�� 50
3 Mandibular Advancement: A Viable Alternative
to Functional Appliances? �� 53
Class II Functional Correction in Clear Aligner Therapy�� 53
The Mandibular Advancement Appliance: Current Features
and Limitations�� 54
Mechanism of Bite Repositioning �� 54
Bite Jump Calibration�� 55
Case Selection�� 58
Tooth Movement Beneath Precision Wings�� 59
Control of Mandibular Incisor Inclination �� 62
Vertical Elastics for Engagement of the Precision Wings�� 62
Efficacy in Comparison to Class II Mechanics�� 63
Contents xv
Maxillary Expansion in Conjunction to Mandibular

Advancement �� 63
Solutions to Deficiencies in the Mandibular
Advancement Appliance�� 63
Improving Engagement of Precision Wings and Mechanism
of Bite Repositioning �� 63
Movement of Teeth Beneath the Precision Wings �� 64
Is Mandibular Advancement a Viable Alternative
to Conventional Class II Correctors? �� 64
References�� 64
4 Problematic Complex Movements: Can Clear Aligners
Treat Them Alone?�� 67
Have Clear Aligners Improved in Achieving Complex
Movements? �� 67
The Challenges of Controlling Maxillary Lateral Incisors�� 68
Invisalign G4 and G7 Attachments�� 68
Alteration in Aligner Geometry for Enhancement of Tooth
Movement�� 69
Combination Treatment with Fixed Appliances�� 70
Auxiliaries for Enhancement of Tooth Movement�� 70
Overcorrection for Improved Predictability of Maxillary
Lateral Incisor Movement�� 70
Torque Control for Maxillary Lateral Incisors�� 71
Restorative Solutions for Maxillary Lateral Incisors�� 73
Bolton Discrepancies �� 74
Missing Maxillary Lateral Incisors�� 74
Root Uprighting �� 76
Elements of Successful Uprighting—The Virtual
Gable Bend�� 76
Elements of Successful Uprighting—Attachment Design�� 77
Treatment Duration�� 79
Coverage of Aligner Material�� 79
Auxiliaries for Uprighting�� 79
Uprighting in Extraction Cases�� 79
Uprighting in Class II Treatment �� 84
Simplifying Complex Movements �� 85
References�� 87
5 Interproximal Reduction�� 89
Interproximal Reduction and Clear Aligner Therapy�� 89
The Indications of IPR �� 90
Decrowding�� 90
Treatment of Class II and Class III Malocclusions�� 90
Tooth Size Discrepancies �� 94
Incisor Uprighting�� 95
Midline Coordination�� 95
Gingival Black Triangles�� 95
Retention�� 96
xvi Contents
IPR Technique�� 96

Considerations when Planning IPR �� 97
Round Tripping and IPR�� 97
Timing of IPR�� 97
Long Term Consequences of IPR�� 99
Reflections on IPR in Clear Aligner Therapy�� 99
References�� 99
6 Dilemmas in Bite Opening�� 101
The Challenge of Deep Bite Correction�� 101
Factors in Bite Opening �� 102
Leveling the Curve of Spee�� 102
Bite Ramps�� 102
G8 Modifications �� 103
Relative Intrusion�� 104
Short Clinical Crowns�� 104
Treatment Protocols �� 106
TAD-Supported Intrusion�� 106
Extraction Cases�� 106
Molar Extrusion �� 108
Improving the Accuracy of Bite Opening�� 112
References�� 112
7 Dilemmas in Open Bite Correction�� 113
Current Strategies for Open Bite Closure�� 113
Efficacy of Movements Associated with Bite Closure�� 114
Absolute Extrusion vs. Relative Extrusion�� 114
Molar Intrusion�� 115
Finishing after Anterior Open Bite Closure �� 118
Factors Affecting Bite Closure�� 118
The Reality of Molar Intrusion during Open Bite Closure�� 118
The Incorporation of Bite Jumps �� 120
TAD-Assisted Molar Intrusion for Bite Closure�� 120
The Reality of Open Bite Closure with Clear Aligner Therapy�� 122
8 Power Ridges: How Powerful Are They?�� 125
Torquing with Clear Aligners�� 125
The Indications of Power Ridges �� 126
Incisor Retraction�� 126
Posterior Protraction�� 126
Lingually Displaced Maxillary Lateral Incisors�� 126
Dental Decompensation for Orthognathic Surgery�� 130
Intermaxillary Forces �� 132
Distalization in Class II Treatment�� 132
The Efficacy of Power Ridges �� 132
Controlling Torque with Clear Aligners�� 134
Contents xvii
9 Overcoming Limitations in Extraction Therapy�� 135

How Predictable Is Extraction Therapy with Clear Aligners? �� 135
Treatment Planning Considerations for Predictable
Extraction Therapy�� 136
Clincheck Development for Extraction Therapy �� 136
Tipping During Space Closure�� 136
Considerations for Posterior Protraction�� 141
Controlling Posterior Torque �� 141
Controlling Incisors During Retraction �� 141
Clinical Management of Extraction Therapy�� 142
Frequency of Aligner Changes�� 142
Tipping During Therapy�� 142
Combination Treatment �� 144
Improving the Efficacy of Clear Aligner Extraction Therapy�� 146
10 The Predictability of Bite Jumps�� 147
What Are Bite Jumps? �� 147
Indications for Bite Jumps �� 148
Growing Patients�� 148
Open Bite Closure�� 151
Orthognathic Surgery�� 152
Dental Functional Shift�� 152
Principles of Bite Jump Use�� 152
Predictability of the Bite Jump�� 152
Timing�� 152
Controversial Uses of the Bite Jump�� 154
Excessive Overjet in Nongrowing Class II Patients�� 154
TAD-Assisted Cases�� 155
Extraction Cases�� 155
Extensive Space Closure�� 156
Mandibular Shifts�� 156
Solutions for Discrepancies Between Clinical Outcomes
and Outcomes Predicted by Bite Jumps�� 158
Growing Patients�� 158
Orthognathic Surgery Cases�� 158
Open Bite Closure�� 160
Dental Functional Shifts�� 160
Optimal Planning of Bite Jumps in Clear Aligner Treatment�� 160
11 Overcoming Limitations in Finishing�� 163
Detailing with Clear Aligner Therapy�� 163
Intra-arch Occlusal Discrepancies �� 164
Discrepancies in the First Order�� 164
Optimizing Tooth Movement�� 166
Discrepancies in the Third Order �� 167
Inter-arch Discrepancies�� 169
Midline Discrepancies �� 169
xviii Contents
Deep Bites�� 169

Anterior Open Bites �� 170
Posterior Open Bites�� 171
Finishing for Treatment Efficacy �� 173
12 When and How to Overcorrect?�� 175
The Various Roles of Overcorrection�� 175
Indications and Methods for Overcorrection �� 176
Unpredictable Tooth Movements �� 176
Unpredictable Jaw Movements�� 180
Occlusal Finishing �� 180
Residual Space Closure�� 181
Distalization �� 182
A Conservative Approach for Overcorrection �� 184
Index�� 187
Abbreviations
AAO American Association of Orthodontists

ANB A-point-nasion-B-point angle
BSSO Bilateral sagittal split osteotomy
CBCT Cone-beam computed tomography
IHA In-house aligner
IMPA Incisor mandibular plane angle
IPR Interproximal reduction
MA Mandibular advancement
PDL Periodontal ligament
RME Rapid maxillary expansion
RPFM Reverse pull face mask
SNA Sella-nasion-A-point angle
SNB Sella-nasion-B-point angle
TAD Temporary anchorage device
U1-SN Upper incisor-sella-nasion angle
VCC Virtual C-chain
VGB Virtual gable bend
xix
Optimizing Diagnosis
and Treatment Planning
1
with Clear Aligner Software
Contents
Clear Aligner Software: A Brief History 1
Major Deficiencies in the Invisalign Clincheck Software 2
The 3M Software 11
Dentsply Sirona Suresmile Software 14
uLab Software 16
The Ideal Clear Aligner Software 19
References 21
lear Aligner Software: A Brief

C [2]. Subsequent generations of the Invisalign
History clear aligner appliance improved both the aligner
material and its capabilities as well as the func-
In orthodontic therapy with clear aligners, the tionality of the software. Typically, software
judicious manipulation of the software consti- innovations allowed for finer control during the
tutes a significant aspect of treatment planning virtual setup through the addition of more fea-
and is critical for successful outcomes. The first tures for tooth positioning, the addition of auxil-
software for clear aligner therapy was introduced iaries, and treatment planning. The technological
by the founders of Align Technology and the development of Invisalign’s clear aligner appli-
inventors of the Invisalign appliance to the ance has expanded its range to the potential treat-
American Congress of Orthodontists in 1999 [1]. ment of more complex malocclusions. However,
The technology adopted computer-aided design/ many of Invisalign’s claims regarding the effi-
computer-aided manufacturing (CAD/CAM) cacy of its appliance, such as the resolution of
techniques to fabricate a series of aligners that significant rotations, extrusions and intrusions of
gradually moved teeth into their desired posi- 2.5 mm in anterior teeth, and root movements of
tions. The first generation of the Invisalign soft- up to 4 mm in posterior teeth, have not been prop-
ware, known as the Clincheck, was primarily erly substantiated [2].
designed for the resolution of simple malocclu- Importantly, in 2015, Invisalign introduced a
sions, such as mild and moderate crowding, number of innovations, including the Clincheck
minor space closure, and minor root movements Pro, alongside alterations in aligner material and
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 1

A. T. Huang, D. Huang, Controversies in Clear Aligner Therapy,
https://doi.org/10.1007/978-3-030-92810-0_1
2 1 Optimizing Diagnosis and Treatment Planning with Clear Aligner Software
the addition of a number of features for the man- simulation fails to realistically model soft tissue
agement of cases involving first premolar extrac- changes produced by orthodontic movements. It
tions [3]. At the time of writing, the current is important that the clinician is mindful of these
version of the Clincheck software is the Clincheck deficiencies so that they can anticipate the effects
Pro 5.0, which is essentially the original of their mechanotherapy and minimize any unfa-
Clincheck Pro with a number of modifications. vorable outcomes.
Since its first iteration, Clincheck has not been In the following chapter, we discuss the major
web-based but needs to be downloaded as an limitations of Invisalign’s Clincheck software,
application. As a result, it remains prone to dis- which range from a lack of functionality for opti-
continuities from server disruptions. The mizing single tooth movement to improper mod-
Clincheck Pro 5.0 remained unavailable as web- eling of soft tissues. In our discussion of single
based software. Notably, the 2015 update incor- tooth movement, we will focus on the judicious
porated into the software the 3D toolbar, which manipulation of attachments. When viable, we
allows for the positioning of individual teeth in will propose solutions for overcoming these limi-
all dimensions, updated its SmartTrack polymer tations in the software. Thereafter, we will survey
aligner material, increased functionality for the the lesser-known alternative software and discuss
placement, orientation, and sizing of attachments how their differing features might be used to the
and cuts, widened capabilities for expansion and clinician’s advantage for delivering successful
contraction of either the maxillary or the man- orthodontic treatment.
dibular arch, and allowed the addition and
removal of sites of interproximal reduction for
space management [3, 4]. The update also added ajor Deficiencies in the Invisalign
M
a number of features to assist in treatment plan- Clincheck Software
ning, including an automatic Bolton analysis, the
visualization of occlusal contacts, and a “dual Single Tooth Movement:
view,” which compares the clinician’s modifica- Incompatibilities in Attachment
tions to Invisalign’s initial setup. Design
In recent years, a variety of dental suppliers
have created competing clear aligner appliances Studies have shown that the addition of attach-
along with their respective software. In 2018, 3M ments onto teeth improves the accuracy of spe-
launched its Clarity clear aligner system and its cific types of orthodontic tooth movements [5].
web-based software for treatment planning. Also Simon et al. reported the best accuracy in the
in 2018, Dentsply Sirona introduced its Suresmile bodily distalization of upper molars of at least
aligners and Elemetrix software as another clear 1.5 mm when movements were supported by
aligner alternative. Both 3M and Dentsply attachments on the tooth surfaces [6]. Clinically,
Sirona’s software differ significantly from that of we have observed that the use of attachments pre-
Clincheck and offer distinct advantages for the vents excessive tipping of molars during distal-
clinician. ization. However, we note that though the
Despite Invisalign’s continued innovations, its difference in accuracy for distalization between
Clincheck Pro software remains limited by a teeth with attachments was greater than that of
number of deficiencies, which potentially com- teeth without attachments, it was not by a statisti-
promise ideal treatment outcomes. These limita- cally significant margin [6].
tions range from lack of optimization for single Studies have also investigated the effects of
tooth movement to a failure in correcting skeletal attachment use on the efficacy of other types of
discrepancies to unrealistic modeling of soft tis- movements. A clinical trial in 2005 supported the
sue changes. For instance, the Clincheck soft- use of attachments to improve the accuracy of
ware currently lacks proper integration of soft rotational movements [7]. Simon et al. observed
and hard tissues. As a result, the treatment that in premolar rotations of >10°, the use of
attachments and the degree of movement per ments so that they cannot be incorporated onto
aligner both had a great impact on predictability tooth surfaces that are deficient in crown length.
[6]. A systematic review in 2015 also recom- This situation arises when attachments are
mended the use of attachments to improve the required for distalizing maxillary molars with
predictability of rotational movements [5]. short clinical crowns (Fig. 1.4). In such cases, the
Nevertheless, other studies have shown conflict- vertical beveled attachment would most ideally
ing results and claimed that the use of attach- support the distalizing movements. However,
ments does not aid in stimulating derotation for because of the short clinical crowns in the maxil-
canines [8]. A 2019 systematic review also con- lary molars, the Clincheck software will auto-
cluded there is a lack of evidence to support the matically trigger the placement of horizontal
use of attachments for derotation [2]. Despite the beveled attachments instead of the desired verti-
lack of consensus in the current evidence, it is cal beveled attachments (Fig. 1.5). As a result, the
still recommended to place attachments on teeth predictability of the distalizing movement is
for derotation, especially exceeding 15°, for
treatment predictability [5].
There is a greater consensus for the use of
attachments in improving the predictability of
extrusive movements. The treatment of vertical
problems, especially deep overbite, is especially
challenging for clear aligners. In a clinical trial,
extrusion was found to be the least accurate tooth
movement [9]. Therefore, it is recommended that
attachments be placed on teeth requiring extru-
sion for predictability [2].
It is evident that the use of attachments is able
to stimulate certain orthodontic movements [10].
In its most recent generations, Invisalign’s
Clincheck Pro has incorporated a number of fea-
tures that expanded the clinician’s control over
attachments as well as their capabilities for con-
trolling tooth movement. Specifically, when the
clinician decides to place an attachment, they are
able to choose its shape, whether an ellipsoid,
mesial or distally beveled vertical attachment, or
a gingival or incisally beveled horizontal attach-
ment (Fig. 1.1). Secondly, the clinician is also
able to determine the size of the attachment—3,
4, or 5 mm in length (Fig. 1.2). Thirdly, the clini-
cian is able to position the attachment both in
terms of its location on the tooth surface and the
orientation of its bevel (Fig. 1.3).
Despite these capabilities, there remain short-
comings in the Clincheck software’s attachment
design that compromise treatment predictability.
Notably, because of the limited configurations
available, the attachment cannot properly adapt
Fig. 1.1 Invisalign allows for a wide range of attach-
to the full range of tooth surfaces. For instance, ments, including the horizontal bevel, vertical bevel, and
the software limits the minimum size of attach- ellipsoid
Fig. 1.4 Horizontal beveled attachments were placed on

molars requiring distalization, whereas the more opti-
mally designed attachments would have been vertical bev-
eled. However, Invisalign’s dimensional limitations
prohibit the placement of vertical beveled attachments due
to the molars’ short clinical crowns
Fig. 1.2 Invisalign Clincheck allows for the clinician to
adjust the length of the adjustment from 3 to 5 mm.
However, at present, the adjustment of other dimensions
(height and depth) remains limited
Fig. 1.5 An Invisalign error message flags the necessary

substitution of horizontal for vertical beveled attachments
due to short clinical crowns
Fig. 1.3 Invisalign Clincheck permits the clinician to

rotate the attachment in all dimensions. This allows the
clinician the freedom to position the active surface of the
attachment to optimize desired tooth movements
limited by the use of a nonideally configured

attachment. The solution for this incompatibility
between attachment size and tooth morphology
would be for the software to allow for attach- Fig. 1.6 Invisalign optimized attachments have been
ments with lengths smaller than 3 mm. Though placed on the right maxillary lateral incisor, the right max-
illary canine, right maxillary second premolar, and the
this option does not yet exist for the most recent
right maxillary first molar
generation of Clincheck software, it has already
been made available by alternative software, such
as 3M Clarity (which we will discuss later in this configured in such a way to enhance specific
chapter). movements, including extrusion, root movement,
During the initial setup of a Clincheck for a and rotation. A recent clinical trial showed that
particular case, the Invisalign technician will optimized attachments allowed for less differ-
often incorporate specialized attachments known ence between predicted and achieved tooth
as optimized attachments (Fig. 1.6). The latter is movement when compared to differences with
non-optimized (conventional) attachments [11]. power ridge in the Invisalign appliance) or the
Ironically, the manner in which these optimized use of attachments is practicable for increasing
attachments are applied actually becomes a limi- the predictability of torquing movements [6]. The
tation in optimizing treatment outcomes. Namely, same study also found that there was no signifi-
once the Invisalign technician places these opti- cant difference in the predictability of maxillary
mized attachments onto tooth surfaces, they can- incisor torque whether the movement was sup-
not be modified by the clinician except for their plemented by an ellipsoid attachment or a power
elimination. The clinician is not able to reposi- ridge [6]. Another study found that minor activa-
tion or reorient the optimized attachment on the tion through the modification of aligner material
tooth surface. At present, if the clinician desires near the gingival margin or the use of properly
the reconfiguration of the attachment, they have configured attachments could improve root con-
to resort to placing a conventional attachment, trol during torquing movements of a maxillary
which may be less ideal for enhancing the spe- central incisor [13]. Though few studies on the
cific type of tooth movement. The most ideal topic have been performed, the current scientific
solution would be for the software to allow the evidence supports the alteration of aligner geom-
clinician greater control over the configuration of etry to enhance torquing movements with clear
the optimized attachments. aligners.
Therefore, the current generation of Clincheck Currently, Invisalign alters aligner geometry
Pro, despite its advances, restricts attachment for torque control through the addition of power
design through firstly, size limitations and sec- ridges, which are lines of pressure close to the
ondly, the default placement of optimized attach- gingival margins of particular teeth (we more
ments. As a result, the clinician must negotiate comprehensively discuss their application and
these limitations by resorting to the use of nonideal efficacy in Chap. 8). There are also points of
configurations or forgoing the placement of attach- pressure that are applied at the incisal region on
ments altogether. Because attachments are often the opposite surface of the tooth. For instance,
required to improve root control and to facilitate a lingual root torque for a maxillary incisor is cre-
variety of movements such as rotation, extrusion, ated through a coupling effect: a larger force is
and distalization, limitations in their design applied at the gingival margin, while a smaller
adversely affect treatment predictability [6]. force in the opposing direction is applied at the
linguoincisal region (Fig. 1.7). The additive
effect of the two forces creates a moment for lin-
ingle Tooth Movement: Limitations
S gual root torque. The Clincheck Pro software
in Torque Application severely limits the clinician in their ability to
incorporate and manipulate power ridges for root
Historically, torque control has been problematic control. Firstly, the power ridges can only be
for clear aligners. Studies have shown clear applied to the maxillary and mandibular incisors;
aligner therapy is not as effective in controlling canines and posterior teeth cannot be equipped
torque as fixed appliances [12]. A clinical trial with power ridges so any torquing movements for
reported an average accuracy of 50.3% for ante- these teeth cannot be enhanced with auxiliary
rior torque movements as compared to 39.95% alterations in aligner geometry. Secondly, the
for premolar rotation and 87.65% for molar power ridges can only be applied on the labial
distalization [6]. Invisalign, along with dental surfaces of the incisors for lingual root torque. At
suppliers, such as 3M, have incorporated a vari- present, power ridges cannot be placed on any
ety of features, including the alteration of aligner lingual surfaces for the enhancement of labial
geometry, for the generation of adequate force root torque.
systems and the enhancement of torque control Thirdly, the clinician can adjust neither the
on specific teeth. Simon et al. has concluded that placement of the power ridge nor that of the pres-
either the alteration of aligner geometry (the sure point. Ideally, the Clincheck software would
crown and root movements by placing lingual

root torque in a rectangular wire in addition to
applying a distalizing force at the crown level
through a strong cinch-back, a power-chain, or
some other means. At present, such simultaneous
crown and root movements cannot be effectively
programmed by the Clincheck software
(Fig. 1.9a,b). If the clinician requests a power
ridge on the mandibular incisors, then the power
ridge would stimulate the root to travel lingually.
However, the crown would also be stimulated to
travel labially. With the addition of the power
ridge on the labiogingival area of the tooth, it
would be difficult to program a simultaneous lin-
gual force to the crown surface. If the clinician
were able to program a pressure point on the
middle third of the crown surface, they would be
able to apply the necessary distalizing force to
prevent excessive labial tipping of the crown.
Fourthly, when power ridges are applied to
maxillary or mandibular incisors, they are placed
for a specific number of aligners or stages. For
instance, in a treatment that requires 20 active
aligners, power ridges may only be applied in 10,
15, or all 20 aligners to the designated teeth. One
of the most critical issues with the application of
power ridges through the Clincheck software is
Fig. 1.7 A coupling effect is created by a labial force that the power ridge is not precisely calibrated for
from a power ridge and a lingual force from a pressure a particular amount of lingual root torque move-
point to generate lingual root torque. PR power ridge; PP
ment. That is, the clinician cannot know the
pressure point.
degrees of lingual root torque applied to the tooth
per each stage of power ridges.
allow the clinician the capability to position both One of the current solutions for these limita-
the power ridge and the pressure point. The con- tions in power ridge and pressure point place-
trol over both auxiliaries would allow the clini- ment and configuration within the Clincheck
cian greater ability to control crown and root software is to apply these auxiliaries with hand
movements in the buccolingual dimension. For instruments during the course of treatment (we
example, there are instances during orthodontic will further discuss the use of hand instruments in
treatment when the clinician desires a lingual Chap. 11). For instance, if during treatment, a
movement of the root while preventing excessive maxillary canine crown requires additional lin-
labial movement of the crown (Fig. 1.8a,b). This gual root torque, one can apply with a horizontal
scenario is common during the late stages of dimple plier a power ridge on the labiogingival
cases involving the extractions of the four first surface of the canine crown in addition to a
premolars. In fixed appliances, for the mandibu- pressure point on the linguoincisal region with a
lar incisors, the clinician can achieve the desired dimple plier.
a b
Fig. 1.8 (a) Buccal root torque applied with both a power power ridge at the cervical area of the labial surface and a
ridge at the lingual surface and a pressure point from the pressure point applied at the labial surface near the incisal
labial. PR power ridge; PP pressure point. (b) Lingual edge. PR power ridge; PP pressure point
root torque with controlled root tipping applied with a
a b
Fig. 1.9 (a) Power ridges can be applied to the cervical teeth. (b) A pressure area has been placed on the lingual
area of the labial surfaces of maxillary and mandibular region of tooth #23. At present, pressure areas cannot be
incisors. However, they cannot be applied in any other determined by the clinician and are placed at default by
region, such as any lingual surface or on the posterior the software
ingle Tooth Movement: Limitations

S creates moments on the anterior and posterior
during Extraction Therapy segments to counteract unwanted crown tipping.
The use of the G6 protocol has been shown to
Extraction therapy remains challenging for clear slightly improve control of first molar movement
aligners (we discuss in detail the efficacy and as compared to the use of conventional attach-
overcoming limitations of clear aligner extrac- ments in cases involving two first premolar
tion therapy in Chap. 9). Studies have shown that extractions [15]. The G6 protocol automatically
despite advances, they still cannot treat complex incorporates a virtual gable bend but it remains
cases, including extraction cases, as successfully unclear the amount of counteracting force the
as fixed appliances [14]. Notably, a clinical trial bend provides to the anterior and posterior seg-
analyzed the differences between actual and pre- ments adjacent to the extraction space. One of the
dicted tooth movements in cases involving the weaknesses of the Clincheck software is that it
extractions of two maxillary first premolars [15]. fails to visualize the movements provided by the
The study found that following treatment, the virtual gable bend. When the clinician requests
molars tipped mesially more than predicted in the virtual gable bend, the software will show
addition to other discrepancies between predicted counteracting forces applied to the designated
and actual movements in incisor torque and verti- teeth but neither the amount of degrees produced
cal position [15]. In 2015, Invisalign introduced nor the specific number of stages (Fig. 1.10). The
the G6 protocol for improving the effectiveness lack of visualization deprives the clinician of a
of extraction therapy with clear aligners [3]. means to control the extent of crown tipping in
Specifically, for cases involving premolar extrac- the adjacent teeth during extraction space clo-
tions, Invisalign programs an optimized retrac- sure. As we will discuss in Chap. 9, crown tip-
tion attachment, optimized anchorage ping during extraction space closure remains one
attachments for the premolars and molars, and of the foremost challenges to extraction therapy
the incorporation of a virtual gable bend, which with clear aligners.
Fig. 1.10 Though a virtual gable bend (VGB) has been cannot be determined the amount of degrees of counter-
requested and forces have been applied to the teeth adja- acting force applied by the VGB per aligner
cent to the extraction space to prevent unwanted tipping, it
eficiencies in Hard and Soft Tissue

D facial outcomes as a result of orthodontic treat-
Modeling ment [18]. Ideally, the Clincheck software could
model facial soft tissue changes by calibrating
Studies have shown that three-dimensional soft them to hard tissue changes in accordance with
tissue modeling is a useful modality for optimiz- demographic norms, such as ethnicity, gender,
ing esthetics during treatment planning [16]. A age, and skeletal class. Alternative software, like
modern form of diagnosis and treatment plan- that of Dentsply Sirona, have begun an integration
ning seems to require the integration of facial between hard and facial soft tissues, through fea-
modeling for the prediction of soft tissue changes tures such as the “lip trace,” which superimposes
as a result of treatment, especially in extraction teeth movements from the frontal view with the
cases and cases involving orthognathic surgery, patient’s actual lip contours.
which are often characterized by extensive facial Similarly, the Clincheck software is limited
changes [17]. by liabilities in its visualization of hard tissues.
At present, the Clincheck software does allow Most notably, though the amount and degree of
for partial integration of soft tissue during the root movement for all teeth are displayed in the
simulation of the patient’s malocclusion. In the software’s assessment table, the roots them-
treatment plan simulation, the clinician can selves cannot be visualized in three dimensions
observe the movements of both the marginal and because they remain concealed by the gingival
attached gingiva along with the simulated move- tissues. As a result, it is difficult for the clinician
ment of the teeth. However, the current software to assess the precise orientation of any root at a
fails to accurately predict the movements of both particular stage during treatment. This unpre-
marginal and attached gingival tissue. For dictability is especially disadvantageous for the
instance, in cases involving the extraction of a treatment of complex cases that involve signifi-
mandibular incisor, the clinician can anticipate cant root movement, such as those involving
the development of a black triangle between the extractions or significant retraction of the maxil-
incisors adjacent to the extraction space, espe- lary and mandibular incisors. As we will discuss
cially in older patients. The Clincheck simulation later in this chapter, the 3M software allows for
of the teeth and soft tissue movements will not the option of viewing teeth movement without
express the development of black triangles and any soft tissues so that the roots can be more
instead models the marginal gingiva so that it precisely visualized at any point in time during
unrealistically fills in the interproximal embra- the simulated treatment plan.
sure between the incisors adjacent to the extrac-
tion space. The poor accuracy of the Invisalign
software’s soft tissue modeling remains a defi- Limitations in the Correction
ciency for the clinician who seeks to predict soft of Skeletal Discrepancies
tissue changes as a result of treatment.
The Clincheck software also lacks any sort of Studies have shown that clear aligners are limited
facial modeling. At present, there is no integration in their capabilities to resolve large anteroposte-
of the facial soft tissues, including upper and lower rior discrepancies [10]. In late 2018, Invisalign
lips, nose, or chin, with hard tissues. Presently, the introduced the mandibular advancement feature
clinician cannot model alterations in the facial soft for the correction of Class II skeletal discrepan-
tissues on the Clincheck software. It would be cies (we discuss the efficacy of the mandibular
more ideal for diagnosis and treatment planning if advancement feature in Chap. 3). Prior to this
there were functional integration of the hard and feature, the Clincheck software resorted to a “bite
soft tissues so that facial features could be mod- jump,” a significant interarch simulated move-
eled along with the teeth. Studies have created 3D ment whether in the anteroposterior, transverse,
simulations of soft tissue norms for forecasting or vertical dimension, as a means of correcting
large skeletal discrepancies in the simulated Limitations in Diagnostic Tools

treatment plan.
As we will further discuss in Chap. 10, the bite The Invisalign software provides a number of
jump is frequently mis-prescribed by both clini- diagnostic tools for the clinician during the
cians and the Clincheck software. Clincheck cur- design of the treatment plan, most notably the
rently offers a tooth movement assessment, Bolton analysis for the mandibular anterior
which expresses the difficulty of individual tooth teeth relative to the maxillary anterior teeth as
movements (Fig. 1.11). However, the software well as the mandibular posterior teeth relative
fails to recognize and indicate the difficulty of to the maxillary posterior teeth, the tooth move-
interarch movements, most notably the bite jump. ment assessment for difficult movements, and
As a result, Clincheck allows clinicians to freely the tooth movement table, which records the
prescribe bite jumps in unrealistic scenarios— total amount of movement in all three orders.
such as a bite jump paired with Class II or Class Though the software allows for the uploading
III elastics for the correction of a large anteropos- of the cephalometric radiograph for reference,
terior skeletal discrepancy or the incorporation of one of its deficiencies is its lack of integration
an anteroposterior bite jump in a nongrowing of cephalometric values, such as SNA, SNB,
patient (Fig. 1.12). In these cases, the Clincheck ANB, U1-SN, IMPA, Sn-GoGn, and other mea-
software allows or automatically prescribes a bite surements important for the development of the
jump in a situation where such an extensive skel- patient’s treatment plan. Cephalometric analy-
etal correction could not feasibly occur. The ses, though there remains a lack of consensus
unrealistic bite jump would produce an overesti- regarding which measurements are the most
mation of the amount of skeletal correction. essential, remain the gold standard for orth-
Ideally, the Clincheck software would allow for odontic clinical routine and the diagnosis of
the incorporation of bite jumps only when indi- growth and developmental abnormalities [19,
cated. The realistic simulation of bite jumps is 20]. Dentsply Sirona has started to functionally
significant for achieving successful outcomes integrate the cephalometric radiograph into
with the correction of skeletal discrepancies with treatment planning by allowing the clinician the
clear aligners. ability to superimpose the simulated teeth
Fig. 1.11 The tooth movement assessment table is displayed at the bottom of the virtual setup in the Invisalign
Clincheck. The blue dot on the simulation indicates a difficult movement
The 3M Software 11
Fig. 1.12 A bite jump is depicted in aligner stage 33. The apy that could feasibly produce such a change in the posi-
software simulates the forward advancement of the man- tion of the mandible, such as the use of the MA appliance
dible from the use of Class II elastics. However, this bite or a Class II orthopedic appliance, like the cervical-pull
jump is unrealistic due to the absence of significant headgear
growth forecasted for the patient or Class II mechanother-
movements over the radiograph. However, like ment [10]. One of the capabilities of the 3M
Invisalign, it has not been able to incorporate software is its free manipulation of attachments
cephalometric analyses into the software. during the treatment planning stage. We have dis-
cussed the importance of attachment shape and
size for the placement of attachments on the
The 3M Software crowns of teeth with abnormal morphology, such
as those with small crown height or diminutive
In 2018, 3M introduced its Clarity aligners along cusps. The 3M software allows for the manipula-
with their software for diagnosis and treatment tion of the attachment in all three dimensions—
planning [21]. Because of their recent develop- length, width, and depth (Fig. 1.13). Notably,
ment, limited research has been performed on the each dimension can be reduced to a minimal
efficacy of the aligners as compared to either size—2 mm in length, 1 mm in width, and
fixed appliances or Invisalign clear aligners. The 0.5 mm in depth for the bar attachment (Fig. 1.14).
3M software is deficient in a number of aspects, Therefore, unlike the attachments of the
particularly in its ability to plan the treatment of Invisalign software, the small volume of 3M’s
complex cases, such as those involving extrac- attachments can be adapted to even abnormally
tions and the correction of severe skeletal dis- small clinical crowns.
crepancies. Nevertheless, the software has Despite the software’s capability for adjusting
incorporated a number of unique features, which attachment size, it remains limited in regards to
offer distinct capabilities for the clinician during shape. At present, the only shapes available are
diagnosis and treatment planning. the bar and bevel. There are also no optimized
default attachments automatically incorporated
by the software. Recent clinical trials have sug-
ptimizing Single Tooth Movement:
O gested that optimized attachments play a role in
Capabilities and Limitations improving the accuracy of movements, particu-
of Attachment Design larly extrusion and rotation [22]. The 3M soft-
ware’s limited range in attachment shape
Studies have shown the significance of attach- adversely affects the predictability of tradition-
ment design for the optimization of tooth move- ally difficult tooth movements for clear aligners.
Fig. 1.13 The attachments in the 3M™ Oral Care Portal small volumes to accommodate teeth with small clinical
software can be customized in all three dimensions: crowns or abnormal morphology
length, width, and height. They can also be minimized to

O Clincheck, the torque points can only be placed
Torque Application and Bite Opening on the labial surfaces of crowns so they cannot
enhance buccal root torque. Therefore, the accu-
Like Invisalign, 3M employs alterations of racy of buccal-lingual torquing movements can
aligner geometry for the enhancement of root be compromised, especially on teeth which typi-
torquing movements. Instead of power ridges, cally struggle with lingual root torque, such as
3M uses individual points of pressure, known as the second molars [22].
“torque points” (Fig. 1.15). The 3M software also For bite opening of deep bite cases, 3M also
limits the placement of their torque points on the allows for bite ramps on the lingual surfaces of
maxillary and mandibular incisors so that they the maxillary anterior teeth. These are slight
cannot be placed on the canines or the posterior enlargements on the lingual surfaces that prema-
teeth. Similar to the power ridges of Invisalign turely occlude with the mandibular anterior teeth
The 3M Software 13
*This chart indicates the parameters of height, width, and length for attachments that the 3M Treatment Design Team works within.
The clinician still has the option to modify within these parameters.
Fig. 1.14 The 3M™ Oral Care Portal software allows for For beveled attachments, the minimum size parameter is
an attachment’s minimum size to be 2 mm in length, 2 mm in length, 1.5 mm in width, and 0.5 mm in depth
1 mm in width, and 0.5 mm in depth for bar attachments.
to application of the bite ramps is the fact that

neither the position nor the size of the bite ramps
can be adjusted by the clinician. In certain cases,
like a Class II patient with both a deep overbite
and large overjet, the default bite ramps are not
adequately gingival to occlude with the mandibu-
lar anterior teeth. As a result, the efficacy of bite
opening can be compromised due to the lack of
disocclusion of the posterior teeth.
Fig. 1.15 The 3M software employs torque points for
lingual root torque, available only on the labial surfaces of
maxillary and mandibular incisors Hard and Soft Tissue Modeling
for posterior disocclusion and additional intru- One of the unique features of the 3M software is
sive forces on the maxillary anterior teeth its detailing of the gingival soft tissues (Fig. 1.17).
(Fig. 1.16). The software automatically installs The software allows for the evaluation of soft tis-
the bite ramps on the lingual surfaces of the max- sue responses to treatment, such as the develop-
illary anterior teeth when it detects the presence ment of black triangles. In 3M’s view of the teeth
of a deep overbite. Bite opening remains one of and gingival movements, the background can
the most challenging movements for clear aligner also be dimmed to better visualize soft tissue
therapy [23]. One of the weaknesses of the 3M changes. Nevertheless, the software has neither
software (and the Invisalign software) in regards been able to incorporate any simulation of facial
Dentsply Sirona Suresmile Software
Like 3M, Dentsply Sirona introduced its

Suresmile clear aligner product and the respec-
tive software in 2018 [24]. The supplier’s model
was unique in that it allowed clinicians an option
of greater control over tooth movements so that
they could treatment plan teeth movements stage-
by-stage without a technician’s initial setup. The
latter option also allows clinicians in-house
aligner (IHA) fabrication.1 Clinicians are able to
Fig. 1.16 The 3M software allows for the placement of
use the Suresmile software for in-office 3D print-
bite ramps on the lingual surfaces of the maxillary anterior ing of aligners at fairly reasonable service fees.
teeth for disocclusion of the posterior teeth during deep The software remains early in its development
bite opening and lacks functions such as optimized attach-
ments and the bite jump for the treatment of com-
plex malocclusions. However, it is unique among
the current forms of software in its advanced inte-
gration of radiographic data.

O
Attachment Design
Fig. 1.17 The gingival architecture in the 3M™ Oral Presently, the Suresmile software offers only
Care Portal software is highly realistic and can be simu- three types of attachments—ellipsoid, horizontal,
lated to show its responses to teeth movement
and vertical (Fig. 1.18a). The software allows for
modification in attachment size, but only in depth
changes as a response to treatment nor has it been and not in length or width. Attachments can be
able to integrate cephalometric analyses. designed for a minimal volume of 5 mm in height,
2 mm in width, and 1 mm in depth (Fig. 1.18b).
These requirements in size limit the placement of
Limitations in the Treatment attachments onto abnormally shaped crowns.
of Complex Malocclusions Likewise, the minimal range of attachment
shapes also limits the enhancement of complex
The 3M software, most likely because of its tooth movements, such as root control.
recent development, has not yet incorporated
specific features for the treatment of complex
malocclusions. Most notably, it lacks a bite jump
option so it cannot accurately model cases involv-
ing extensive interarch changes, such as mandib-
ular autorotation as a result of maxillary molar
intrusion, mandibular growth in a growing
patient, and orthognathic surgical corrections. At 1
Suresmile refers to this option as do-it-yourself (DIY)
present, the software seems less capable than fabrication of aligners. However, because of the contro-
Invisalign in the treatment of skeletal discrepan- versial associations of DIY aligners with direct-to-
consumer products, which completely omit a medical
cies and remains most adequate for malocclu- professional from treatment, we elect to use the alterna-
sions of mild to moderate severity. tive term, in-house aligner (IHA), for the rest of the book.
Dentsply Sirona Suresmile Software 15
Fig. 1.18 (a) The Suresmile software allows only hori- Suresmile software, attachment volume can be minimized
zontal, vertical, and ellipsoid attachments. At present, no to 5 mm in height, 2 mm in width, and 1 mm in depth
optimized attachments are available. (b) In the Dentsply

O whether automatically or manually requested by
Torque Application and Bite Ramps the clinician. As a result, there are currently no
means for Suresmile to disocclude posterior teeth
The Suresmile software remains undeveloped in in deep bite cases.
its features for the enhancement of torquing
movements. We have discussed how the modifi-
cation of aligner geometry can enhance torquing Hard and Soft Tissue Modeling
movements, which can be difficult for aligners
due to the nature of the material [13]. Suresmile The Suresmile software is advanced in its integra-
currently lacks any modifications of aligner tion of hard and soft tissue for treatment planning.
material for the purpose of torque in the manner Specifically, it allows for the “lip trace” option,
of power ridges or torquing points. which superimposes the patient’s photographed
Similarly, the Suresmile software lacks the lips from the frontal smile photo onto the simu-
capability to add bite ramps in deep bite cases, lated tooth movements (Fig. 1.19). The feature
sions, such as a bite jump function, a mandibular

advancement feature for the treatment of growing
individuals, optimized attachments, and a virtual
gable bend for extraction situations. The clinician
should take caution in using the product and the
software in treating cases of complexity, such as
those involving extractions, skeletal discrepan-
cies, and orthognathic surgery.
uLab Software
The uLab software is unique among the various

Fig. 1.19 The Suresmile software is unique in that it
allows the superimposition of the patient’s lips from their software in that it gives the clinician the freedom
smile photo onto the simulated teeth movements to create the initial setup and plan all tooth move-
ments during the treatment planning stage. This
can be useful for planning the extent of intrusion more independent type of treatment planning
of the maxillary incisors, as well as the amount of seems to represent the future form of clear
expansion in the maxillary posterior segments. aligner therapy. There is an option for a software-
The software has also incorporated realistic mod- coordinated tooth setup either for the maxillary
eling of the patient gingiva in response to tooth and mandibular anterior teeth or both of the
movements. It offers a “comparison gingiva” entire arches, but it remains rudimentary and
option, which juxtaposes the initial and final gin- always requires additional modification on the
gival architecture. These features for soft tissue part of the clinician to achieve ideal alignment
modeling facilitate treatment planning but the and occlusion. The current software is character-
real-time simulation of other soft tissues, such as ized by versatility in attachment design and the
lips in profile, have not yet been introduced. enhancement of tooth movements during treat-
The software has also assimilated a number of ment planning but remains limited in its ability
hard tissue diagnostic tools. For instance, the to treat cases of greater than mild to moderate
cephalometric radiograph can be superimposed severity.
over the simulated teeth movements so they can
be assessed with more certainty. Secondly, the
software is capable of linking CBCT imaging so ptimizing Single Tooth Movement:
O
that both root movements and the bony housing Attachment Design
can be visualized (Fig. 1.20). Studies have shown
that the use of 3D imaging can allow for more The uLab software allows for adjustment of
accurate predictions of orthodontic tooth move- attachments in all three dimensions—length,
ment [25]. The CBCT integration would allow for width, and depth. It has also incorporated a
such applications as eruption compensation for “copy-paste” function so that clinicians can save
permanent teeth, whether impacted or otherwise, a specific attachment design to a library for reuse
planning for the degree of expansion or proclina- on another tooth in the future (Fig. 1.21). The
tion, and the planning of root movements. attachments have been designed for a wide range
of sizes and shapes and can be adapted for small
clinical crowns and teeth with abnormal mor-
Treatment of Complex Malocclusions phology. Nevertheless, at present, the software
has not yet incorporated default or optimized
The Suresmile software currently lacks specific attachments for complex tooth movements,
features for the treatment of complex malocclu- though an update is planned for fall 2020.
uLab Software 17
Fig. 1.20 The Suresmile software allows for integration of CBCT imaging and the cephalometric radiograph with the
simulated tooth movements
Fig. 1.21 The uLab

software allows for a
wide variety of
attachments and
pressure points
Fig. 1.22 Pressure points can be placed on all surfaces and fully manipulated in the uLab software

O gration of the facial soft tissue, such as lips in
Torque Application and Bite Ramps frontal view, lips in profile, and does not possess
any feature similar to the Suresmile software’s
Like 3M software, uLab employs pressure points “lip trace.”
for the application of either buccal or lingual root The software allows for viewing of the
torque. The uLab software permits the placement untraced cephalometric radiograph but cannot
of the pressure points anywhere on the crown of superimpose it over the simulated teeth move-
both anterior and posterior teeth so that lingual ments. It has not been developed for integration
root torque can be enhanced by applying a pres- of CBCT imaging and therefore cannot visualize
sure point on the gingival third of the labial sur- root movements or the bony housing along with
face and another on the incisal third of the lingual the simulated tooth movements.
surface (Fig. 1.22) [13].
Though bite ramps are currently unavailable
either default or manually placed, attachments Treatment of Complex Malocclusions
can be positioned onto the lingual surfaces of the
maxillary incisors and adequately sized for func- The uLab aligners and software are adequate for
tion as bite ramps. Because these lingual attach- mild to moderate severity malocclusions but are
ments can be positioned and sized with relative unequipped for severe malocclusions. It cur-
freedom, they can be functional even in cases rently lacks a bite jump feature for skeletal dis-
with deep overbites and significant overjet. crepancies, any form of mandibular advancement,
and any protocols for bite opening, extraction
therapy, and growing individuals. The clinician
Hard and Soft Tissue Modeling is not recommended to employ uLab for com-
plex malocclusions. Nevertheless, for less severe
The uLab software remains primitive in both its cases, uLab is the most suited for IHAs, for the
hard and soft tissue modeling. At present, it can- clinician to control all stages of tooth movement
not display real-time changes to the gingiva as a from initial setup to 3D printing aligners
result of teeth movement. It also lacks any inte- in-house.
The Ideal Clear Aligner Software 19
The Ideal Clear Aligner Software of these recommendations, the following repre-
sents a paradigm for a software that can optimize
In light of the numerous deficiencies that mark the accuracy of tooth movement, incorporate
the current forms of software, we conclude this modern and comprehensive diagnostic and treat-
chapter by proposing the characteristics that ment planning tools involving both hard and soft
comprise an ideal clear aligner software tissue modeling, and realistically plan for the
(Table 1.1) Recent editorials have also advocated treatment of complex malocclusions (Table 1.2).
the creation of an AAO-based staging software
for doctor control over data, workflow, and the
delivery of treatment, as opposed to partnering Optimizing Tooth Movement:
with an external corporation [26]. A software Attachment Design
controlled by the orthodontic specialty organiza-
tion would create a more flexible treatment option The ideal software should allow for the clinician
for patients. Also, the collection and analysis of to freely customize attachments in all three
data would allow for improved efficacy of dimensions—length, width, and depth. The
evidence-based clear aligner treatments. In light minimal dimensions should be small enough to
Table 1.1 Comparison between major types of clear aligner software

Type of software Invisalign Clincheck 3M software Suresmile uLab
Attachment Wide range of shapes. Limited shapes. Limited shapes. Wide range of shapes.
design Optimized and default No optimized or No optimized or No optimized or
available. default. default. default.
Limitations on minimal Small volume available Limitations on Copy and paste
size. for teeth with abnormal minimal size. function.
morphology. Small volume
available for teeth
with abnormal
morphology.
Torque Power ridges for torque Pressure points for No alterations in Pressure points can be
application and application: limited to torque application: aligner geometry for applied in any area.
bite opening labial surfaces and limited to labial torque application. Fully adjustable by
incisors. No clinician surfaces and incisors. No bite ramps clinician.
adjustment. No clinician available for bite Lingual attachments
Bite ramps on lingual adjustment. opening. can be employed as
surfaces of U3-3. No Bite ramps on lingual bite ramps on any
clinician adjustment. surfaces of U3-3. No surface. Fully
clinician adjustment. adjustable.
Hard and soft Limited; primitive Real-time gingiva Real-time gingiva Limited; primitive
tissue modeling gingiva modeling, no modeling, no facial soft modeling. Lip trace gingiva modeling, no
facial soft tissue tissue modeling. option available. facial soft tissue
modeling. No integration of Integration of CBCT, modeling.
No integration of cephalometric and cephalometric No integration of
cephalometric and CBCT radiographs. radiograph cephalometric and
CBCT radiographs. superimposition CBCT radiographs.
available.
Treatment of Bite jump, mandibular No bite jump or No bite jump or No bite jump or
complex advancement, mandibular mandibular mandibular
malocclusions extraction protocols advancement. advancement. advancement.
available. Virtual gable bend No extraction No extraction
Able to treat complex available for extraction protocols. protocols.
malocclusions. cases. Mild-moderate Mild-moderate
Mild-moderate severity severity severity
malocclusions. malocclusions. malocclusions.
In-house aligner Not compatible. Not compatible. Option available. Compatible.
fabrication
Table 1.2 Characteristics of an ideal aligner software Hard and Soft Tissue Modeling
Parameter Characteristics
Attachment design Freely customizable attachments Real-time hard and soft tissue responses to orth-
in all three dimensions and sizes. odontic treatment would be fully integrated into
Torque application Free placement of pressure
points and lines.
an ideal software. The software would allow for
Hard and soft tissue Integration of soft tissue and the superimposition of the cephalometric radio-
modeling CBCT modeling. graph with the simulated teeth movements along
Treatment of • Realistic bite jump with the initial and predicted final measurements.
complex • Surgical planning The software would also incorporate soft tissue
malocclusions • Standardization of extensive
movements modeling, including the responses of the gingival
• Realistic growth modeling tissues, lips, and soft tissue chin to tooth move-
In-house aligner Compatible. ment. The integration of CBCT imaging would
fabrication allow for visualization of root movements and
the bony housing.
adapt to small clinical crowns, such as small
vertical attachments on diminutive maxillary
molars for distalization. Attachment shapes Treatment of Complex Malocclusions
should also be available in a wide array to
enhance complex tooth movements, such as The ideal software would develop realistic and
coupled, tear-drop shaped attachments, in the comprehensive features for the treatment of com-
fashion of Invisalign’s optimized root control plex malocclusions. The bite jump, which we
attachments, which can be placed facing oppo- previously discussed is often overused or unreal-
site directions on a tooth crown to enhance root istically applied in treatment plans involving
control. skeletal discrepancies, could be monitored by the
software so that alerts or warnings could be
flagged for movements that are either unpredict-
ptimizing Tooth Movement: Torque
O able or unfeasible. In other words, the tooth
Application movement assessment tool, which flags difficult
tooth movements, would also monitor for diffi-
The ideal software would provide the clinician cult interarch movements.
with fine control of tooth movements in the third The ideal software would also incorporate
order. The uLab software currently permits the more realistic surgical planning so that surgical
greatest freedom for the manipulation of the movements would not only be simulated by bite
third order. Similarly, the ideal software would jumps but also in the manner of virtual model
allow for the placement of multiple pressure surgery, which is the most commonly accepted
points on either labial or lingual surfaces and in method of planning for orthognathic surgery
both anterior and posterior teeth. The accuracy [28]. For instance, in a two-jaw surgery to correct
of torquing movements has been shown to be a Class III skeletal patient, the software would be
problematic. Studies on the efficacy of tooth able to precisely simulate the movements of a
movement in nonextraction Invisalign cases mandibular setback in addition to a maxillary
have shown statistically significant differences impaction and advancement rather than resort to
between predicted and actual facial crown a simple bite jump, which would only approxi-
torque in the mandibular first and second molars mate the surgery by displaying a mandibular set-
as well as the maxillary first and second molars back. Ideally, the software would also simulate
[27]. The application of pressure points in these surgeries for TMJ disorders such as osteotomies
problematic areas would allow for greater pre- and distraction osteogenesis in the treatment of
dictability in torque control [6]. TMJ ankylosis. Such simulations would be simi-
References 21
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Adapting Clear Aligner Therapy
to Interceptive Treatment for Early
2
Mixed Dentitions: Are They
the Same as Late Teen or Adult
Treatment?
Contents
Clear Aligner Therapy for Interceptive Treatment: Challenges
and Considerations 23
Major Features of Clear Aligner Interceptive Treatment 24
The Deficiencies of Interceptive Treatment with Clear Aligners 34
Solutions to Current Limitations in Clear Aligner Interceptive Treatment 40
The Viability of Interceptive Treatment with Clear Aligners 50
References 50
Clear Aligner Therapy has not been rigorously tested in the scientific lit-
for Interceptive Treatment: erature. However, early clinical trials and clinical
Challenges and Considerations application suggest a number of deficiencies in
Invisalign First that limit both treatment predict-
Historically, clear aligner therapy was originally ability and efficacy. Phase I therapy poses unique
designed for the treatment of mild malocclusions challenges for clear aligner therapy. Though
in adults. However, in 2019, Invisalign adapted Invisalign First features can replace certain
their clear aligners for interceptive treatment modalities in Phase I treatment with conventional
(Phase I treatment) of children in the early mixed fixed appliances, they often require supplementa-
dentition with the introduction of a group of fea- tion or significant modification to achieve the
tures collectively known as Invisalign First treat- effects necessary for the treatment of the full
ment [1]. The updates included optimized support range of malocclusions in the early mixed
attachments and force systems for increased pre- dentition.
dictability of dental expansion, optimized reten- One of the most critical components of con-
tion attachments for improved adherence to teeth ventional Phase I therapy is growth modification
with short clinical crowns, eruption compensa- in growing individuals for the correction of Class
tion for erupting incisors, canines, and premolars, II and Class III skeletal discrepancies. The pre-
and treatment planning modalities for move- cise timing of intervention for Class II discrepan-
ments of primary teeth [1]. Because of their cies remains controversial, though studies have
recent development, the efficacy of these updates shown that significant long-term improvement of

https://doi.org/10.1007/978-3-030-92810-0_2
24 2 Adapting Clear Aligner Therapy to Interceptive Treatment for Early Mixed Dentitions: Are They…
Class II skeletal relationships occurs when treat- expander, mandibular lingual arches, transpalatal
ment is started at the outset of puberty [2]. arches, and transpalatal-Nance arches.
Nevertheless, there is an increased acceptance In this chapter, we discuss the effectiveness of
that though early intervention in Class II maloc- clear aligners in their application to Phase I ther-
clusions may not be more effective long-term, it apy. We describe the major features of the most
is more efficient than later treatment [3]. current form of clear aligners for Phase I therapy,
However, there is a greater consensus that early its applications for treatment, its deficiencies, and
intervention is most optimal for the correction of propose current and future solutions to maximize
Class III skeletal discrepancies. It has been shown its effectiveness.
that maxillary protraction (traditionally with
rapid maxillary expansion and reverse-pull face-
mask) is most successful when performed in the ajor Features of Clear Aligner
M
early mixed dentition [4]. Importantly, conven- Interceptive Treatment
tional Phase I therapy also typically includes
rapid maxillary expansion (RME), involving the Expansion
widening of the maxillary basal bone prior to the
fusion of the maxillary sutures at 14–15 in For interceptive treatment, Invisalign clear align-
females and 15–16 in males [5]. Early expansion ers rely heavily on expansion for arch length
is often used for the purposes of the correction of development. The treatment effects of expansion
transverse discrepancies, increased effectiveness with clear aligners simulate those of traditional
of maxillary protraction, elimination of func- Phase I appliances with expansion capabilities,
tional shift, and the resolution of arch length defi- such as the lip bumper, the inner bow of the head-
ciency. Baccetti et al. observed that RME gear, RME, mandibular lingual arches, transpala-
treatment in the pre-peak period of puberty tal arches, transpalatal-Nance arches, and certain
resulted in greater transverse skeletal changes functional appliances. At present, Invisalign has
than those when RME treatment was initiated in incorporated optimized expansion attachments in
the post-peak period [6]. Therefore, it is essential order to supplement the predictability of expan-
that an adaptation of clear aligner therapy for sion movements (Fig. 2.1). There has been a lim-
interceptive treatment allows for the incorpora- ited number of studies that have assessed the
tion of growth modification and orthopedic treat- efficacy of expansion with clear aligners in the
ment effects. child or teenage population, but there have been
One of the challenges of Phase I therapy is clinical trials investigating its efficacy in adults.
that significant dental changes occur over a short It has been observed that maximum expansion
time frame. For instance, an effective appliance with Invisalign should be limited to 2–4 mm [8].
for the interceptive treatment of patients in the A recent study showed that in adults, Invisalign
early mixed dentition needs to accommodate the could achieve 68.31% efficacy of crown expan-
exfoliation of primary teeth and the eruption of sion movement for maxillary first molars [9].
succedaneous teeth. This can be problematic for Another study found a 72.8% efficacy of expan-
an appliance like clear aligners, which cannot be sion for the maxilla and 87.7% efficacy of expan-
readily modified during a course of aligners. sion for the mandible [10]. However, it is
Phase I therapy also requires the management important to note that most of the crown expan-
of children, who are generally not as compliant or sion movement occurred through buccal tipping
as motivated as the adult or late teenager popula- rather than bodily expansion or skeletal expan-
tion [7]. Clear aligner therapy may require certain sion. Houle et al. found that Clincheck’s predic-
modifications to address hyperactive or noncom- tion of expansion involved more bodily movement
pliant children, especially because aligners are than clinically observed, while more buccal tip-
more susceptible to wear and breakage than tradi- ping was found than predicted [10]. Therefore,
tional Phase I fixed appliances, i.e., rapid palatal the clinician should be mindful of performing
Fig. 2.1 Optimized expansion attachments have been incorporated on the right mandibular first and second primary
molars (#S and #T). Both are programmed for buccal translation, as indicated by the tooth movement assessment table
extensive expansion movements, i.e. >4 mm, effects of the appliance in adults and offers lim-
even in the child population, because the clear ited evidence regarding the accuracy of the erup-
aligner appliance primarily relies on buccal tip- tion compensation algorithm.
ping for expansion effects. Later in this chapter,
we discuss approaches to controlling expansion
during interceptive treatment within a safe range. Optimized Attachments
For interceptive treatment, Invisalign has

Eruption Compensation designed specialized optimized attachments for
patients in the mixed dentition. As previously
For the orthodontic treatment of patients in the mentioned, optimized attachments are automati-
early mixed dentition, the appliance must accom- cally placed on both primary and permanent teeth
modate for the frequent exfoliation of primary to supplement all types of movements. Like the
teeth and the eruption of succedaneous teeth. optimized attachments for permanent teeth, those
Invisalign First has incorporated eruption com- for the early mixed dentition also enhance a wide
pensation features into its appliance to plan and range of movements, such as rotation, root tip-
maintain space for permanent teeth (Fig. 2.2) [1]. ping, and extrusion (Fig. 2.3). In contrast to both
Invisalign claims that its eruption compensation the optimized and nonoptimized attachments for
algorithm can accurately predict and create the permanent dentition, the Invisalign First opti-
spacing necessary for the maxillary incisors, mized attachments are sized for adaptation to the
canines, and premolars [11]. Eruption compensa- small clinical crowns of primary teeth. However,
tion features have been available for adolescents nonoptimized attachments are still limited in the
with Invisalign Teen, which was introduced in sense that they cannot be minimized beyond a
2008. However, research has focused on the size of 3 mm.
Fig. 2.2 Invisalign First’s eruption compensation algorithm has planned for the eruption of the maxillary right lateral
incisor and the mandibular left canine
etal Class II discrepancies. The feature sought to

simulate the mandibular repositioning effects of
Class II functional appliances, such as the Twin-
Block, MARA, Herbst appliance, and other acti-
vators. It employs “precision wings,” which are
extensions from both the maxillary and man-
dibular aligners that hold the mandible in a for-
ward position (Fig. 2.4). The feature is only
available for patients in the mixed dentition,
which applies to Invisalign First and Invisalign
Teen patients. Only a limited number of pilot
studies has investigated the efficacy of the man-
dibular advancement feature, which we examine
further in Chap. 3.
Phase II Treatment
Fig. 2.3 On the left maxillary first molar, the left second Like more traditional forms of Phase I, intercep-
maxillary primary molar, and the left second mandibular tive treatment with clear aligners should be com-
primary molar, optimized attachments enhance move- pleted as efficiently as possible to minimize
ments such as expansion and derotation
treatment time [12]. After its completion, patients
are typically monitored at 6–12 month intervals
Mandibular Advancement until the eruption of the remaining permanent
teeth. Because it is common that a significant
In 2018, Invisalign introduced its mandibular period of time will elapse before the patient is
advancement feature for the correction of skel- dentally mature enough for Phase II, the clinician
Fig. 2.4 The mandibular advancement feature is simu- between the eighth and ninth stage. Precision cuts have
lated in the Clincheck through the extensions from the been designed on the maxillary primary canines and man-
maxillary and mandibular molars. The simulation demon- dibular primary first molars for vertical elastics to main-
strates a 1 mm advancement of the mandible occurring tain a forward repositioned bite
will have to consider retention measures. These Duration of Aligner Wear

may involve more traditional appliances because,
at present, Invisalign does not provide retainers Studies have shown that teenage patients may
that can accommodate the transition of dentition prefer removable clear aligners to fixed appli-
in patients between phase I and II. Interceptive ances for reasons such as improved esthetics, less
treatment with clear aligners will typically be fol- hard and soft tissue irritation, no dietary restric-
lowed by Phase II treatment in the form of the tions, and fewer social issues [13]. However, pre-
Invisalign Teen appliance, which shares a num- pubescent children may have more frequent
ber of features with Invisalign First, including the compliance issues with clear aligners than older
eruption compensation algorithm. populations such as chewing or playing with the
appliance leading to breakage. In these cases, the
duration for each aligner may have to be short-
Frequent Midcourse Corrections ened from the typical 14 days to 5 or 7 days in
order to minimize breakage and facilitate
During the course of interceptive treatment with treatment.
clear aligners of patients in the mixed dentition,
erupting permanent teeth can often lead to poor
tracking, even with the application of the erup- Treatment Applications
tion compensation algorithm. In such cases, the
clinician must either order a midcourse correc- Interceptive treatment with clear aligners can
tion or additional aligners to continue treatment achieve typical Phase I objectives, such as the
by accommodating for erupting permanent teeth. alleviation of an anterior crossbite, space manage-
One of the characteristics of Invisalign First is the ment for erupting permanent teeth, or correction
greater frequency of midcourse corrections when of anterior crowding, by simulating the dental
compared to that of adult or teen Invisalign effects of a maxillary and mandibular 2 × 4 setup
treatment. in conventional fixed appliances (Fig. 2.5). In the
case illustrated in Fig. 2.5, patient V.Z. received a However, because clear aligners are not able
course of conventional Phase I appliances, includ- to produce orthopedic effects, for more severe
ing treatment with high-pull headgear and lip discrepancies, they may require supplementation
bumper. The lip bumper expanded the mandibular in the form of traditional orthopedic appliances,
arch and relieved crowding in the region of the such as headgear, the reverse-pull facemask
mandibular right canine but the mandibular left (RPFM), and the RME. Though Invisalign claims
canine remain blocked out. A course of clear that its mandibular advancement appliance can
aligners further expanded the arch to create space produce orthopedic effects, it remains uncertain
for the mandibular left canine. Phase I treatment whether the appliance can effectively promote
was followed with Invisalign Teen clear aligners mandibular growth. The clear aligner itself and
during phase II. In this fashion, interceptive treat- treatment planning with the software may have to
ment with clear aligners can function like conven- be modified for the incorporation of orthopedic
tional Phase I appliances to relieve crowding and appliances during the course of interceptive
create space for permanent teeth. treatment.
Fig. 2.5 Patient V.Z. received an initial course of treat- ated for the left mandibular canine with the course of clear
ment with high-pull headgear and lip bumper. Afterward, aligners. Phase II treatment involved detailing and finish-
the mandibular arch was further expanded with a course ing, reduction of residual overjet, and correction of
of Invisalign First clear aligners. Adequate space was cre- canines and molars into Class I relationships
Fig. 2.5 (continued)





he Deficiencies of Interceptive
T not calibrated to any standard of growth and
Treatment with Clear Aligners tends to overestimate the extent of mandibular
growth in the prepubescent patient because the
imitations in Growth Modification
L software will automatically finish the occlusion
and Prediction as ideally as possible. As a result, the bite jump
may produce an unfeasible treatment outcome.
Invisalign has claimed that its mandibular The clinician must be cautious that the software
advancement appliance can correct Class II dis- does not perform unrealistic movements with
crepancies by promoting mandibular growth in a bite jumps during treatment planning with
“more efficient” manner than conventional func- Invisalign First.
tional appliances [14]. These strong claims of
greater efficiency have not been supported by any
substantial scientific evidence. Like other appli- Range of Expansion
ances when first introduced for orthodontic treat-
ment, the mandibular advancement feature The Invisalign First appliance currently allows
requires further research regarding its treatment the clinician to select among several options for
efficacy. the range of expansion desired for treatment
The Invisalign First appliance is also limited planning a given case. The choices range from
in its compatibility with more conventional <2, 2–4, 4–6, 6–8, to >8 mm. Studies have shown
orthopedic appliances whose potential treatment that in growing children (average age of 8 years,
effects have been established, most notably the 1 month) treated with RME, the average total
headgear. High-quality studies have noted that expansion was measured at the molar crown to be
headgear treatment can produce skeletal changes 3.60 mm, with mean skeletal expansion at the
in the short term, as demonstrated by a mean molar of 1.60 mm (minimum: 1.12 mm, maxi-
annual change in SNA angle (−1.63°/year, 95% mum: 1.97 mm) [16]. In the treatment of growing
Confidence Interval = −2.20 to −1.06°/year) in children with conventional appliances that
treated patients compared to untreated patients expand less aggressively, such as the inner bow
(though the amount of skeletal change long-term of the headgear, studies have observed an average
seems to diminish when comparing headgear increase of 2.31 mm in intermolar width [17]. It
treated to untreated patients) [15]. The Invisalign is unlikely that Invisalign First, a non-orthopedic
First appliance does not readily permit the inte- appliance whose limit has been indicated to be
gration of appliances such as the headgear during 2–4 mm, can achieve a greater amount of expan-
a course of aligners. However, for Class III cor- sion than those observed in conventional modali-
rection, the reverse-pull facemask (RPFM) can ties of expansion, particularly the RME, which
be incorporated into aligner wear through preci- induces palatal sutural opening. Therefore, it is
sion cuts at the first maxillary molars or alterna- problematic that Invisalign First allows for
tive means, such as bonding metal buttons onto choices of expansion that range greater than
the first maxillary molars and creating button cut- 4 mm because such expansion movements, when
outs in the series of aligners. modeled in the treatment simulation, would be
In addition to these limitations in the appli- unrealistic.
cation of orthopedic forces, the Invisalign First
appliance also lacks realistic modeling of man-
dibular growth in prepubertal patients. Adaptation to Short Clinical Crowns
Presently, the appliance employs the bite jump
to simulate mandibular growth during a course As previously discussed, Invisalign First has
of aligners (Fig. 2.6). However, the bite jump is incorporated optimized retention attachments
for increased adherence of its aligners [11]. ulations that are more prone to the breakage of
However, the attachments are often still inade- fixed appliances than adults [18]. The parents of
quate to retain the aligner to deciduous teeth children who elected for Invisalign First over
with short clinical crowns and to prevent dis- fixed appliances may oppose any fixed appli-
lodging. These optimized attachments are also ance because, at the outset, they desired for their
not modifiable by the clinician, so their sizes and children no restrictions in eating and brushing.
positions may not be ideal for retention onto the It is also important to note that the application
deciduous crown. of force directly onto teeth with metal buttons
Inadequate crown retention can also be prob- may result in undesired side effects, such as
lematic for elastics wear in Invisalign First extrusion of molars during Class II or Class III
patients. During interceptive treatment with elastics, or mesialization and rotation of maxil-
clear aligners, intermaxillary elastics and elas- lary molars with RPFM wear (Fig. 2.7).
tics for RPFM wear are often applied from pre- In the case illustrated in Fig. 2.7, the patient
cision cuts on either or both the maxillary and I.T. received Phase I treatment with clear aligners
the mandibular aligners. Even with the addition supplemented with RPFM. The protraction force
of retention attachments, the short clinical was directed to buttons on the maxillary left first
crowns of deciduous teeth lend themselves to premolar because of lack of retention on the short
aligner dislodging during elastics wear. An clinical crowns of the first permanent molars. The
alternative to frequent dislodging can be to bond RPFM allowed for forward advancement of the
metal buttons on the teeth for elastics wear. maxilla but caused the mesialization of the max-
However, the clinician should be mindful that illary left first premolar leading to potential
children and prepubescent adolescents are pop- impaction of the maxillary left canine. The
Fig. 2.6 A bite jump was programmed into the Clincheck between stages 36 and 37. It advanced the mandible 3 mm
forward.
patient received a refinement course to distalize standardized cephalometric measurements such

the maxillary left first premolar and to ensure as IMPA and U1-SN. Therefore, the final incisor
adequate space for the eruption of the maxillary positions modeled by the Clincheck do not accu-
left canine. I.T’s case evidences the importance rately project what may occur as a result of
of monitoring for adverse side effects when treatment.
incorporating additional appliances to clear
aligners during interceptive treatment.
Availability of Clinical Preferences
oftware Calibration for Treatment

S During the submission of a new patient case
Planning prior to the development of the treatment simula-
tion, Invisalign allows the clinician to select cer-
Invisalign claims that its eruption compensation tain preferences, including whether to
algorithm for incisors, canines, and premolars is incorporate the mandibular advancement fea-
“highly accurate.” Clinically, we have observed ture, bite opening mechanics, tooth movement
that the accuracy of the algorithm can be unpre- restrictions, overjet correction, midline correc-
dictable. It tends to underestimate the amount of tion, space management, teeth that require erup-
space necessary for the eruption of the permanent tion compensation, and modalities for
tooth, so the clinician must often increase the decrowding, i.e., anterior interproximal reduc-
space originally planned by the software tion, posterior interproximal reduction, expan-
(Fig. 2.8). sion, and proclination. However, these clinical
Similarly, the software has not calibrated tooth preferences still lack important features for treat-
positions and movements to cephalometric data. ment planning, including the placement of preci-
As a result, the simulated inclinations of the max- sion cuts, timing of attachment placement, and
illary and mandibular incisors are often not repre- limitations for the expansion of the mandibular
sentative of their actual positions as reflected by intercanine width.
Fig. 2.7 Patient I.T. was treated with RPFM in combina- jumping the anterior crossbite and advancing the maxilla.
tion with clear aligners (Invisalign First). The protraction However, it also mesialized the maxillary left first premo-
force could not be applied to precision cuts respective to lar despite encapsulation by the aligner. The undesired
the first maxillary molars due to their short clinical crowns movement of the maxillary left first premolar led to pos-
and problems with retention. As a result, the RPFM was sible impaction of the maxillary left canine. Consequently,
applied with elastics to buttons on the left maxillary pri- we incorporated a short refinement course to distalize the
mary canine and then the left maxillary first premolar left maxillary first premolar to create adequate space for
after it was erupted. The protraction force assisted in the eruption of the left maxillary canine


Class III discrepancies, especially of greater

severity. Studies have shown that children with
Class III malocclusions who received treatment
with protraction facemask demonstrated signifi-
cant skeletal changes when compared to non-
treated controls, including ANB: +3.66°, SNA:
+2.10°, SNB: −1.54°, and significant changes in
the palatal and mandibular plane angles [21]. The
facemask’s protraction force can be delivered
with elastics directly to the aligner’s precision
Fig. 2.8 The eruption compensation algorithm occasion- cuts on the maxillary first molars or canines or to
ally underestimates the space necessary for the eruption of buttons bonded onto the maxillary first molars
permanent teeth. In this case, the space afforded the erupt- (Fig. 2.9). In this manner, the protraction force
ing maxillary second premolar (both maxillary first pre-
molars have been extracted) is insufficient can be directed approximately through the center
of resistance of the maxilla. These concepts are
illustrated in Fig. 2.9, in which patient W. W. was
Post-Interceptive Treatment treated during phase I with RPFM and two
Retention courses of clear aligners. The protraction force
was applied through elastics from the RPFM to
At present, Invisalign First has not developed a precision cuts incorporated into the aligner
form of retention to maintain the results of Phase respective to the first maxillary molars. Therefore,
I treatment. This lack is especially problematic the patient was able to wear the RPFM while the
because the outcomes of Phase I treatment are clear aligners corrected other aspects of the mal-
often prone to relapse or becoming undone occlusion, including decrowding of the maxillary
through natural growth and development. For and mandibular anterior teeth and creation of
instance, arch expansion of initially constricted space for the maxillary lateral incisors. The ante-
maxillary or mandibular arches tends to relapse rior crossbite was corrected through the combi-
toward their original dimensions [19, 20]. Also, nation of RPFM and clear aligner movements
without retention, crowding tends to recur and through both the normalization of maxillary inci-
can potentially impact erupting permanent teeth. sor inclinations and forward movement of the
To prevent such adverse effects, clinicians have maxilla.
to create specialized forms of retention to pre- However, the appliance still lacks features for
serve the outcomes of interceptive treatment with compatibility with other major orthopedic appli-
clear aligners. ances, such as the headgear. At present, the head-
gear can be incorporated into clear aligner
interceptive treatment as a phase prior to a course
olutions to Current Limitations
S of Invisalign First aligners. That is, the patient
in Clear Aligner Interceptive would wear the headgear until Class II molar
Treatment relationships were improved to Class I and subse-
quently, the patient would receive a course of
Incorporating Orthopedic Appliances aligners to achieve the other objectives of Phase I
treatment, such as normalization of overjet or
We have discussed that the Invisalign First creation of adequate space for erupting perma-
appliance allows for RPFM use during a course nent teeth. Alternatively, the headgear could be
of aligners. The addition of orthopedic protrac- combined with a course of aligners. For instance,
tion force is essential for the correction of true the maxillary first molars can be banded, while
Fig. 2.9 Patient W.W. was treated with a combination of to the first maxillary molars. After the initial and single
RPFM and clear aligners (Invisalign First). The protrac- refinement course, we achieved ideal overjet and overbite,
tion force aided in jumping the anterior crossbite and pro- Class I molar relationships, and adequate space for erupt-
moting the forward movement of the maxilla. The RPFM ing permanent teeth
force was directed via elastics to precision cuts respective

the maxillary aligner is cut short immediately fabricated to encapsulate the molar band, while
distal to the maxillary second premolars so that the headgear tube remains uncovered for use
the patient can wear the headgear during treat- (Fig. 2.11a,b). The distalizing effects of the head-
ment (Fig. 2.10). In Fig. 2.10, patient S.M. gear could be incorporated into the Clincheck
received an initial course of cervical headgear simulation along with the rest of the tooth move-
treatment prior to a course of clear aligners. The ments at an average rate of 0.25 mm of movement
cervical headgear was continued during the per aligner. This design would allow for the com-
course of clear aligners by sectioning the maxil- bination of the distalizing force supplied by the
lary aligners immediately distal to the maxillary aligner and the orthopedic effects of the headgear
second premolars. In this manner, the distalizing and would be the most effective out of the three
forces of the cervical headgear supplemented approaches in the early correction of Class II
those of the clear aligners to maintain the maxil- discrepancies.
lary molars during retraction of the maxillary Similarly, other Class II correcting distalizing
anterior teeth. The cervical headgear could also appliances besides the headgear can be incorpo-
continue to provide orthopedic effects during the rated into the Invisalign First appliance.
course of the clear aligners. Traditionally, Class II distalizers may have been
Both of the previously mentioned approaches employed in a separate initial stage prior to a series
are viable, but theoretically, the most effective of clear aligners. Instead, precision cuts can be
solution would be to have the aligner specially incorporated on the distal of the maxillary canine
Fig. 2.10 Patient S.M. first received 8 months of Phase I continued CHG wear and to maintain Class I molar rela-
treatment only with cervical headgear. After Class I tionships. The second course of aligners corrected minor
molars and reduction of overjet were achieved, the patient discrepancies in alignment (derotation of the left maxil-
received two courses of clear aligners. During the first lary lateral incisor) and achieved ideal posterior
course, bands were kept on the first maxillary molars for interdigitation


a b
Fig. 2.11 (a) The headgear can be functionally com- forces to the maxillary arch. (b) The clear aligner is cut
bined with the clear aligner to incorporate orthopedic out for molar band encapsulation around the tooth, while
effects into treatment and provide additional distalizing allowing for headgear use
Retention to Small Clinical Crowns
The small clinical crowns of the deciduous teeth

pose difficulties for aligner retention, especially
when they receive supplementary forces,
whether through intermaxillary elastics or
RPFM. Retention can be enhanced on these teeth
through a number of methods. Firstly, lingual
attachments can be placed on deciduous teeth
with small clinical crowns, especially when the
aligner encapsulating the tooth will receive addi-
tional force from intermaxillary elastics. At pres-
ent, the clinician can manually add lingual
Fig. 2.12 The clear aligner can be cut out to accommo- attachments on any of the deciduous teeth.
date a bonded distalizer, which can be activated at every Secondly, clinicians may consider a different
appointment
type of gingival finish to the aligner when con-
fronted with problems of retention. Though
and the first maxillary molar, along with button cut- Invisalign only permits a “scalloped” gingival
outs for the bonded distalizing appliance (Fig. 2.12). finish, an aligner that finishes slightly on the gin-
As in the case of the headgear, the distalizing giva would increase retention for teeth with
effects of the distalizer can be incorporated into the small clinical crowns (Fig. 2.13). As discussed in
Clincheck at an average rate of 0.25 mm of move- Chap. 1, 3M’s clear aligner currently finishes
ment per aligner. Therefore, the distalizing effect of slightly on the marginal gingiva (Fig. 2.14). The
the bonded distalizer can be supplied to the maxil- clinician may prefer such an alternative to over-
lary arch in addition to other dental movements come retention issues with small clinical crowns.
performed by the clear aligners for greater distal- Thirdly, the clinician may add retention grooves
izing forces as well as decreased treatment time. to the aligner respective to the deciduous tooth
gingival problems and recession [22]. Ideally,

the software would recognize expansion
beyond physiological limits and alert the clini-
cian in a fashion similar to the tooth movement
assessment. However, such alerts presently
only exist for individual tooth movements with
the tooth movement assessment in the current
version of Clincheck and not for the extent of
maxillary expansion. During clear aligner
interceptive treatment, the clinician should be
cautious to expand the maxilla within physio-
Fig. 2.13 Invisalign aligners invariably use a scalloped
gum line finish. This design feature may allow for
logical limits.
improved patient comfort compared to aligners that finish
on the marginal gingiva. However, the scalloped finish
will be a limiting factor for retention to teeth with small oftware Calibration for Eruption
S
crowns, such as the deciduous tooth #A shown above
Compensation and Incisor Position
The treatment simulation often fails to accurately

predict the space necessary for erupting perma-
nent teeth. The clinician should be mindful of the
amount of space planned by the software and
modify eruption space as needed. Ideally, the
algorithm for eruption compensation will be
improved in future generations of Invisalign
First.
It is also important that the clinician be mind-
ful of incisor positions that are not accurately
Fig. 2.14 3 M aligners are fabricated with a gum line modeled on the treatment simulation. The clini-
finish, which would allow for greater retention to teeth cian can approximate incisor changes with the
with small clinical crowns, such as deciduous teeth
tooth movement table, but they have not been
calibrated with cephalometric data, which
with a small clinical crown (Fig. 2.15a–c). The remains a future software solution for accurately
addition of grooves is not currently available planning incisor positions.
through the Invisalign software. However, the
clinician can manually add an indentation onto
the aligner with a hand instrument for increased Expanding Clinical Preferences
retention. This method can be useful when the
clinician decides to initiate intermaxillary elas- Many of the practitioner’s clinical preferences,
tics or RPFM wear. such as the placement of elastics, the timing for
placement of attachments, and limits on expan-
sion of the mandibular intercanine width, remain
Expansion Limits unavailable during the initial submission of the
patient case. These factors are often critical for
A number of the options for expansion exceed the success of treatment outcomes and have to be
the recommended limit of 2–4 mm. Expansion controlled with modifications to the Clincheck
beyond these limits could cause future muco- simulation.
a b
Fig. 2.15 (a) The retention groove on the maxillary right Retention dimples can also be created on both the facial
lateral incisor can increase retention of the aligner to a and lingual surfaces of the aligner in the interproximal
tooth with a short clinical crown. (b) The retention groove areas of posterior segments. These dimples can be created
can be created with a 3 mm horizontal dimple plier. (c) with a 1 mm dimple plier
Post-Interceptive Treatment tion spaces for the permanent teeth. The latter can
Retention be a more preferred option for parents who desire
for their children a more comfortable form of
As discussed, the lack of explicit clear aligner retention. Ideally, in the future, Invisalign will
retention protocols creates issues for patients provide clear aligner retainers with specific erup-
between Phase I and II treatment. At present, the tion spaces or pontics and with more durable
clinician must either fabricate traditional Hawley material than its SmartTrack for the transition
retainers or Essix retainers modified with erup- period following interceptive treatment.
The Viability of Interceptive 4. Franchi L, Baccetti T, McNamara JA. Postpubertal

assessment of treatment timing for maxillary
Treatment with Clear Aligners expansion and protraction therapy followed by
fixed appliances. Am J Orthod Dentofac Orthop.
Since the introduction of the Invisalign First 2004;126:555–68.
appliance in 2019, clear aligners have become 5. Haas AJ. Long-term posttreatment evaluation of rapid
palatal expansion. Angle Orthod. 1980;50(3):189–217.
more viable as a modality for interceptive treat- 6. Baccetti T, Franchi L, McNamara JA Jr. The cervical
ment. The appliance’s additional features—its vertebral maturation (CVM) method for the assess-
force systems and optimized attachments, its ment of optimal treatment timing in dentofacial ortho-
eruption compensation algorithm, its retention pedics. Semin Orthod. 2005;11(3):119–29.
7. Oliveira P, Tavares R, Freitas J. Assessment of moti-
attachments for short clinical crowns, and other vation, expectations and satisfaction of adult patients
measures—do expand its capabilities for clear submitted to orthodontic treatment. Dental Press J
aligner treatment in children and young adoles- Orthod. 2013;18(2):81–7.
cents. However, the appliance suffers from a 8. Boyd RL. Esthetic orthodontic treatment using the
Invisalign appliance for moderate to complex maloc-
number of critical deficiencies that potentially clusions. J Dent Educ. 2008;72(8):948–67.
limit the success and predictability of treatment 9. Zhou N, Guo J. Efficiency of upper arch expan-
outcomes. Most notably, there is no evidence to sion with the Invisalign system. Angle Orthod.
demonstrate that the current appliance itself can 2020;90(1):23–30.
10. Houle JP, Piedade L, Todescan R Jr, Pinheiro FH. The
produce orthopedic effects. Also, it cannot be predictability of transverse changes with Invisalign.
readily combined with many conventional ortho- Angle Orthod. 2017;87(1):19–24.
pedic appliances with established effectiveness. 11. Align Technology. Invisalign First. 2019. https://info.
In this chapter, we discussed a number of aligntech.com/lp/Invisalign-First/faq. Accessed 13
Sep 2020.
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ance to overcome its inherent limitations. We treatment. Aust Dent J. 2017;62(1):4–10.
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headgear and the RPFM for maximal use of clear 14. Align Technology. Mandibular Advancement. 2020.
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the future development of clear aligner intercep- 2020.
15. Spyridon NP, Kutschera E, Memmert S, Gölz L,
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correction of skeletal discrepancies and more tematic review and meta-analysis. Eur J Orthod.
complex malocclusions. 2017;39(2):176–87.
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H. Evaluation of the effects of rapid maxillary
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Mandibular Advancement:
A Viable Alternative to Functional
3
Appliances?
Contents
Class II Functional Correction in Clear Aligner Therapy 53
The Mandibular Advancement Appliance: Current Features and Limitations 54
Solutions to Deficiencies in the Mandibular Advancement Appliance 63
Is Mandibular Advancement a Viable Alternative to Conventional Class II
Correctors? 64
References 64
lass II Functional Correction

C improved maxilliomandibular relationship [4].
in Clear Aligner Therapy Over the next 100 years, the Andresen-Haupl
activator was further refined into various bion-
Since the introduction of the “bite-jumping” ators and functional regulators, most notably the
appliance by Norman Kingsley in 1879, func- Twin Block appliance developed by William
tional appliances have developed into a corner- Clark and an appliance designed by Rolf Fränkel,
stone of orthodontic treatment for skeletal which employs buccal shields and lip pads to
malocclusions in growing individuals [1]. The reduce lip and cheek pressure and to normalize
first functional appliances and their use were pio- abnormal oral muscular activity. Fixed functional
neered in Europe during the early twentieth cen- appliances were also introduced in the early
tury, in parallel to the growth of fixed appliances twentieth century by Emil Herbst in 1905. His
in the United States [2]. In 1902, Pierre Robin appliance was composed of bilateral telescoping
introduced the simple monobloc appliance for pistons extending between the maxilla and the
the treatment of mandibular retrognathia and jaw mandible from either orthodontic bands or cobalt
expansion [3]. Robin’s monobloc served as a chromium caps. The pistons apply a protrusive
model for Viggo Andresen and Karl Haupl, who force to the mandible for its forward reposition-
modified an upper Hawley retainer with a lingual ing and the correction of Class II malocclusions.
flange for the treatment of Class II malocclusions The Herbst appliance still remains in use as a
by allowing for the forward positioning of the Class II corrector and has also been modified into
mandible for a more ideal occlusion and an less intrusive forms, such as the FORSUS, which

https://doi.org/10.1007/978-3-030-92810-0_3
54 3 Mandibular Advancement: A Viable Alternative to Functional Appliances?
applies a similar protrusive force to the mandible high risk of bias, as all the orthodontists involved
through nickel-titanium springs contained within in the trial are financially tied to Invisalign.
pistons attached to molar bands [5]. Therefore, the trial is questionable evidence for
The efficacy of both fixed and removable the purpose of evaluating the efficacy of the man-
functional appliances for Class II correction has dibular advancement appliance. To date, because
been extensively researched, with particular the mandibular advancement appliance has only
attention to their skeletal effects and relationship recently been made available for clinical use, no
to mandibular growth. Studies have shown that controlled clinical trials evaluating its efficacy
the use of Class II functional appliances resulted have been published.
in a statistically significant difference of 1.79 mm Despite its supposed efficacy, there are signifi-
in annual mandibular growth compared to a con- cant limitations to the mandibular advancement
trol group, as measured by various cephalometric appliance that require management for successful
values [6]. Similarly, a meta-analysis of the man- outcomes. In this chapter, we describe the current
dibular changes during Fränkel-2 (FR-2) treat- state of the modality and its deficiencies.
ment of growing patients with Class II Afterward, we discuss current and future solu-
malocclusions showed that the appliance had a tions for its effective application in the treatment
statistically significant effect on mandibular of Class II malocclusions.
growth, as measured by mandibular body length,
total mandibular length, and mandibular ramus
height [7]. However, there is an increasing con- he Mandibular Advancement
T
sensus that though Class II functional correctors Appliance: Current Features
do induce an increase in mandibular length com- and Limitations
pared to untreated subjects, the improvement in
mandibular projection is either negligible or Mechanism of Bite Repositioning
insignificant [8]. Nevertheless, though the true
skeletal effects of both fixed and removal func- One of the most significant characteristics of
tional appliances remain undetermined, it has Invisalign’s mandibular advancement appliance
been shown that they are effective in correcting is the duration of engagement between the preci-
molar relationships and reducing overjets in sion wings of the maxillary and mandibular
Class II malocclusions through a combination of aligners. When the precision wings are engaged,
dentoalveolar and skeletal effects [9]. the patient’s mandible is repositioned forward,
In 2017, Align Technology introduced the typically in cumulative 2 mm increments relative
mandibular advancement modality as a clear to centric relation, although clinicians are able to
aligner alternative to conventional fixed and program 4 mm or even 6 mm increments.
removable appliances for the correction of Class Conventional fixed functional appliances (FFAs),
II malocclusions [10]. The company claimed that such as the Herbst, also act through a mechanism
their device could function as a “simpler, more of mandibular repositioning. The FFAs have been
efficient, and patient-friendly treatment option shown to induce both statistically significant den-
than functional appliances to treat teen Class II toalveolar and skeletal changes, though primarily
patients” [10]. The basis of these claims rests on dentoalveolar [11]. Most notably, in Zymperdikas
a prospective clinical trial with only preliminary et al.’s systematic review, FFAs induced signifi-
results not published in a refereed orthodontic cant retroclination of the upper incisors and sig-
journal. Align also reports that the preliminary nificant proclination of the lower incisors [11].
results showed “statistically significant correc- Also, the same study showed that FFA-treated
tion of Class II malocclusion,” though it remains groups showed slightly greater mandibular skel-
unclear by what parameter and against what con- etal growth, as well as a statistically significant
trol group this correction was measured [10]. The restriction on maxillary growth [11]. However,
quality of the trial is also compromised by its though Align claims that their mandibular
advancement appliance can effectively replace

conventional functional appliances, there is no
evidence to show that it can achieve similar den-
toalveolar and skeletal treatment effects. One of
the critical differences between conventional
functional appliances and the mandibular
advancement appliance lies in their mechanism
of mandibular repositioning. The mandibular
advancement appliance lacks a mechanism by
which to connect the maxillary and mandibular
precision wings. Therefore, the patient is not nec-
essarily biting in the forward position, as the
wings likely remain disengaged for a significant
proportion of time during daily use of the appli- Fig. 3.1 The Fränkel-2 (FR-2) is a removable functional
ance. Similarly, the wings of the appliance are appliance that the patient uses for at least 14 hours/day for
mandibular repositioning and retraining of the perioral
disengaged for a large percentage of the 8–9 hours muscles
when the patient is asleep. As a result, the effi-
cacy of the appliance at Class II correction may
be compromised because the patient’s mandible severe Class II discrepancy in an adolescent
is only in a protruded position part-time. male. Like the Herbst appliance, the FR-2 forces
This mechanism of bite repositioning differs the patient to bite into a protruded position during
from conventional functional appliances such as closure. In contrast to the part-time mechanism
the Fränkel-2 and the Herbst appliance, which of the mandibular advancement appliance, the
functions by keeping the mandible in a continu- continuous bite-jumping of the Herbst and FR-2
ous protrusive position by connecting the maxil- allows for full-time forward repositioning of the
lary and mandibular arches through telescopic patient’s mandible.
arms. As a result, this continuous “bite-jumping”
is ensured by the appliance, while the patient can
still move into lateral excursive movements dur- Bite Jump Calibration
ing functions such as speaking and eating [12].
During mouth closure, the patient must bite into At present, the mandibular advancement appli-
the protruded position. There is evidence that the ance allows for 2 mm incremental bite jumps until
Herbst appliance’s continuous “bite-jumping” an edge-to-edge position (or 1 mm reverse overjet
induces the stimulation of condylar growth in for overcorrection). This mechanism of sequential
response to forward positioning of the mandible advancement is similar to that for certain modifi-
and may also contribute to the favorable redirec- cations of the Twin Block appliance, as well as for
tion of mandibular growth [13]. Similarly, a con- specific FR-2 protocols [14]. In particular, the
ventional removable functional appliance such as Twin Block appliance can be adjusted for con-
the Fränkel-2 also employs a mechanism of controlled gradual advancement of the mandible
tinuous bite repositioning through its setup of through advancement screws (Fig. 3.3) [15]. This
interconnected lingual flanges, buccal shields, modification allows for increased flexibility of the
and lip bumper shields (Fig. 3.1). Treatment with appliance and accommodation for patients with
the FR-2 has also shown statistically significant limitations to significant mandibular protrusion.
enhancement of both mandibular body length, In contrast, the gradual advancement in the man-
total mandibular length, and mandibular ramus dibular advancement appliance is not as precisely
height [7]. The FR-2 can effectively treat severe calibrated as a modified Twin Block, especially
Class II malocclusions, like the patient in Fig. 3.2, because of the former’s part-time mechanism of
which demonstrates the successful treatment of a bite repositioning. Therefore, the mandibular
Fig. 3.2 An 11-year-old male with a skeletal Class II sis shows the achievement of ideal overjet and overbite,
malocclusion with a severely prognathic maxilla, retrog- normalization of the maxillary incisors, control of torque
nathic mandible, 100% overbite, and 14 mm overjet was in the mandibular incisors, and Class I relationships
successfully treated with the FR-2. Cephalometric analy- bilaterally

ANB discrepancy, and Class II malocclusions

characterized by mandibular retrognathia and
orthognathic maxillae. For example, clinicians
have recommended the Herbst appliance is most
indicated in Class II malocclusions with man-
dibular retrognathia, an ANB angle ≥4°, and an
overjet ≥6 mm [17]. Studies have also shown
that optimal timing for Class II correction is dur-
ing or slightly after the onset of pubertal growth,
typically between stages 3 and 4 of cervical ver-
tebral maturation [18].
Clinically, we have observed that similar to
Fig. 3.3 In a version of a modified Twin Block, advance- conventional functional appliances, the mandibu-
ment screws allow for gradual incremental advancement lar advancement appliance yields the most suc-
of the mandible during therapy cessful outcomes in Class II malocclusions with
orthognathic maxillae and retrognathic mandi-
advancement appliance’s bite jumps are often bles (Fig. 3.4). In the case of patient K.Z., a
inaccurately calibrated and do not achieve the 12-year-old female sought orthodontic treatment.
increments planned by the software. It is also She showed a Class II malocclusion, character-
important to note that sequential advancement can ized by an orthognathic maxilla and retrognathic
be advantageous for patient acceptance and com- mandible, a 6 mm overjet, an 80% overbite, and
fort, but Invisalign does offer the option of initial Class II end-on canines and molars bilaterally.
maximum protrusion if the clinician prefers it to She received clear aligner therapy with a course
incremental bite jumps [16]. of mandibular advancement followed by a single
course of refinement. At the conclusion of treat-
ment, we achieved ideal overjet and overbite and
Case Selection Class I canines and molars on the left side but
were unable to achieve Class I canines and molars
Similar to treatment with conventional Class II on the right, whose canines and molars finished
functional appliances, case selection for the slightly end-on Class II. We attribute this result to
mandibular advancement appliance is critical for a Bolton discrepancy with maxillary deficiency,
successful outcomes. Studies have shown that as well as the deficiencies in the mandibular
many of the conventional Class II functional advancement appliance, which likely did not
appliances are most suitable for the treatment of deliver an adequately aggressive propulsive force
moderate to severe overjet (>6 mm), a significant to the mandible.
Because the mandibular advancement appli- ANB angle <4° and overjet <6 mm and less capa-
ance also relies on mandibular growth to achieve ble of treating more severe discrepancies
Class II correction, its optimal timing is most (Table 3.1).
likely during or slightly after the onset of puber-
tal growth, coinciding with that of the Twin
Block and other conventional functional appli- ooth Movement Beneath Precision
T
ances. However, we have observed that due to the Wings
mechanical limitations of the mandibular
advancement appliance, it is most effective for During treatment with conventional Class II
the treatment of Class II malocclusions with an functional appliances such as the Herbst appli-
Fig. 3.4 Patient K.Z. was treated with the mandibular which we attribute to a maxillary tooth size deficiency
advancement appliance. She received an initial course of (small maxillary lateral incisors) and inadequacy of the
mandibular advancement followed by a single course of appliance in delivering continuous and aggressive protru-
refinement. We achieved ideal overjet and overbite and sion to the mandible. The superimpositions compare the
Class I canines and molars on the left side, but we were patient’s initial and 9 months into treatment following the
unable to achieve Class I relationships on the right side, initial course of mandibular advancement


Table 3.1 Suggested parameters for use of the MA

appliance
Parameter Diagnosis
Skeletal diagnosis Mandibular retrognathia
ANB <4°
Overjet <6 mm
Fig. 3.6 Precision cuts are incorporated on the maxillary

canines and mandibular first premolars for vertical elas-
tics wear during mandibular advancement. The use of ver-
tical elastics can be problematic due to frequent dislodging
from lack of retention in the maxillary and mandibular
posterior segments
Fig. 3.5 The mandibular advancement appliance’s preci- dibular incisor proclination, which is historically
sion wings will encapsulate the maxillary and mandibular
first molars and second primary molars on both sides. The an adverse side effect of a number of the conven-
precision wings will limit freedom of movement for the tional Class II functional appliances, including
encapsulated teeth the FR2, Herbst, MARA, and Twin Block [19].
Initial case studies also suggest an improved con-
ance and the MARA, the teeth encapsulated by trol of mandibular incisor inclination with the
the main apparatus are limited in their move- appliance, as evidenced by measurements of
ments because they function as anchor units for mandibular incisor inclination which remained
the maxillary and mandibular dental arches. The stable pre and posttreatment [20]. However, to
mandibular advancement appliance likewise lim- date, no randomized clinical trials have been pub-
its teeth movement in the segments with the pre- lished to corroborate Align’s claims regarding the
cision wing extensions. Typically, for patients in appliance’s efficacy in controlling mandibular
the mixed dentition, the maxillary and mandibu- incisor inclination [20].
lar first molars and the second primary molars are
contained within these segments (Fig. 3.5). The
efficacy of their individual movements is reduced ertical Elastics for Engagement
V
because firstly, attachments cannot be placed to of the Precision Wings
enhance the performance of difficult movements
and secondly, the design of the precision wings The mandibular advancement appliance includes
does not permit full encapsulation of the anchor a feature to secure the precision wings during
teeth. As a result, the first course of aligners with patient wear. Specifically, precision cuts are
mandibular advancement will often require a incorporated on both primary maxillary canines
refinement course to move the anchor teeth into (#C and #H) and both primary mandibular first
proper alignment and occlusion. molars (#L and #S) for vertical elastics, which
supposedly assist in maintaining engagement
between the maxillary and mandibular precision
ontrol of Mandibular Incisor
C wings (Fig. 3.6). This method of vertical elastics
Inclination is problematic because they frequently cause dis-
lodgment of both maxillary and mandibular
Align Technology has claimed that its mandibu- aligners, even when the strength of the elastics is
lar advancement appliance is able to limit man- low, at ¼″, 2 oz. or ¼″, 3 oz. This frequent dis-
Solutions to Deficiencies in the Mandibular Advancement Appliance 63
lodging results from the lack of retention of the

aligners to the short clinical crowns of the decid-
uous teeth, which serve as the anchor units for the
vertical elastics. Often, these vertical elastics
have to be avoided altogether during a course of
mandibular advancement because they are coun-
terproductive and dislodge the aligners rather
than supplement engagement of the precision
wings.
fficacy in Comparison to Class II

E
Mechanics Fig. 3.7 During mandibular advancement, Invisalign fre-
quently programs overexpansion of the maxillary poste-
Most of the preliminary trials and case studies rior segments, which may lead to poor tracking and
investigating the efficacy of the mandibular dislodging of the maxillary aligners
advancement appliance have focused on milder
cases of Class II malocclusion, particularly ments of the individual maxillary posterior teeth
patients whose ANB < 4°. This suggests that the but also the efficacy of the mandibular advance-
appliance’s range of efficacy may be limited to ment feature. The clinician should be prudent in
cases of mild severity and not those with monitoring the amount of expansion planned
ANB > 4°. Though no clinical trials have during interceptive treatment, especially when it
directly investigated the efficacy of clear aligner involves mandibular advancement.
therapy for the correction of Class II malocclu-
sions, a number of case studies have shown suc-
cessful correction of mild cases [21]. Solutions to Deficiencies
Consequently, it is still questionable whether in the Mandibular Advancement
the mandibular advancement appliance is supe- Appliance
rior in efficacy to the exclusive use of Class II
mechanics in the treatment of mild Class II I mproving Engagement of Precision
malocclusions. Wings and Mechanism of Bite
Repositioning
axillary Expansion in Conjunction

M As previously discussed, one of the major limita-
to Mandibular Advancement tions to the current iteration of the mandibular
advancement appliance is its method of bite repo-
During mandibular advancement, the Invisalign sitioning, which results in disengagement
software often plans for significant maxillary between the precision wings for a significant pro-
posterior expansion. The expansion planned fre- portion of time during daily wear. A solution
quently exceeds realistic amounts of physiologi- would be to unify the maxillary and mandibular
cally stable molar expansion of 4 mm, which are precision wings into a single unit to ensure more
those achieved by orthopedic appliances, such as regular engagement (Fig. 3.8). This modified
the rapid maxillary expander [22]. As a result of mandibular advancement appliance, modeled on
this overexpansion, the aligner material in the conventional Class II correctors such as the FR-2,
maxillary posterior segments with the precision Herbst, or other activators, would still allow for
wings often tracks poorly and begins to dislodge lateral excursive movements but would force the
from its respective teeth (Fig. 3.7). Therefore, the patient into the desired advanced position during
overexpansion compromises not only the move- protrusive movements. Therefore, the efficacy of
I s Mandibular Advancement
a Viable Alternative to Conventional
Class II Correctors?
The mandibular advancement appliance remains

largely untested in regards to its efficacy in the
correction of Class II malocclusions. Align
Technology’s early claims of its comparable (or
superior) efficacy relative to conventional Class
II functional appliances remain unsubstantiated
Fig. 3.8 The maxillary and mandibular precision wings
by the scientific literature and rest on a prelimi-
can be united into a single unit to ensure more continuous nary clinical trial with high risk of bias and ques-
and aggressive mandibular protrusion during patient wear. tionable conclusions. The current appliance,
As shown on the left, the modified aligner with the united which is modeled after the Twin Block, is charac-
maxillary and mandibular precision wings can be worn
nightly for bite repositioning. As shown on the right, con-
terized by a number of mechanical limitations,
ventional clear aligners can be worn during the day for including a bite repositioning method that results
optimal tooth movement in constant disengagement between its parts and
a pattern of vertical elastics wear that frequently
the appliance could be potentially improved by dislodges the maxillary and mandibular aligners.
more securely tethering the maxillary and man- Early evidence suggests that case selection is piv-
dibular precision wings. otal for successful outcomes: the appliance is
most ideal for the treatment of mild Class II mal-
occlusions with orthognathic maxillae, retrogna-
ovement of Teeth Beneath
M thic mandibles, and ANB < 4°.
the Precision Wings We anticipate that randomized clinical trials in
the future will continue to clarify the efficacy of
The single-unit modified mandibular advance- the MA appliance relative to both conventional
ment appliance can be incorporated into an aligner Class II functional appliances and Class II
wearing regimen that allows for more accurate mechanics with clear aligners. The future optimi-
movement of the teeth that would be typically zation of the mandibular advancement appliance
encapsulated within the precision wings. The likely lies in the improvement of its bite reposi-
patient can wear the single-unit modified aligner tioning mechanism for more aggressive and con-
at night for 14–16 hours/day, including during tinuous mandibular protrusion.
sleep. In the daytime, for 8–10 hours/day, the
patient can wear a traditional clear aligner without
precision wings to allow for optimal movement of References
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functional appliances to midcentury. Am J Orthod
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vidual teeth and the treatment effects of the man- Dent J. 2015;218:123–8.
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Problematic Complex Movements:
Can Clear Aligners Treat Them
4
Alone?
Contents
Have Clear Aligners Improved in Achieving Complex Movements? 67
The Challenges of Controlling Maxillary Lateral Incisors 68
Root Uprighting 76
Simplifying Complex Movements 85
References 87
ave Clear Aligners Improved

H were less accurate at 40% [2]. Incisor intrusion,
in Achieving Complex Movements? at an accuracy of 35% for the mandibular inci-
sors, remained consistently low across both trials
Historically, certain complex tooth movements [2]. Poor control of overbite due to difficulties
have been problematic for clear aligner therapy. with intrusive movements of anterior teeth has
One of the first clinical trials analyzing the effi- been cited as a longstanding limitation of clear
cacy of tooth movement with clear aligners dem- aligner therapy [3]. A comparison between these
onstrated that specific movements were lacking two clinical trials suggests that despite significant
in accuracy when predicted tooth positions were advances in clear aligner technology during the
compared with actual positions [1]. Notably, the last decade, the same teeth movements, including
least accurate movement was extrusion, particu- rotation, extrusion (of molars), and incisor intru-
larly of the maxillary and mandibular incisors sion, though improved in accuracy, remain
[1]. The study also found a low accuracy for the problematic.
rotation of canines and maxillary lateral incisors Similarly, complex movements such as tooth
[1]. A 2020 follow-up study to the aforemen- uprighting remain unpredictable. Studies of
tioned clinical trial found that though the overall extraction treatment with Invisalign indicate that
accuracy of movements improved, rotation was the molars adjacent to extraction spaces do not
the least accurate movement, especially of maxil- achieve bodily movement as predicted and are
lary lateral incisors, canines, premolars, and instead characterized by undesired mesial tipping
molars [2]. The accuracy of maxillary incisor and inadequately controlled root movement
extrusion was improved to 55%, though the despite the incorporation of Invisalign extraction
extrusion of maxillary and mandibular molars protocols [4]. Tooth uprighting, especially

https://doi.org/10.1007/978-3-030-92810-0_4
68 4 Problematic Complex Movements: Can Clear Aligners Treat Them Alone?
requiring extensive root movement, remains a during intrusion of adjacent teeth, particularly the
challenge for clear aligner therapy. maxillary central incisors. The G4 and G7 gen-
There have been a variety of methods pro- eration optimized attachments have allowed for
posed by clinicians to address these deficiencies improved predictability of maxillary lateral
in clear aligner therapy. Studies have recom- movement, as supported by a comparison
mended the judicious use of additional attach- between the 2009 and 2020 studies on the effi-
ments for problematic movements, especially for cacy of tooth movement with Invisalign [1]. The
vertical movements in the anterior segments [5]. studies show that the accuracy of maxillary inci-
Clinicians have also observed that the use of sor extrusion has improved between 2009 and
overcorrection can be beneficial for achieving 2020. This improvement may likely be a result of
difficult movements [3]. Additionally, the use of Invisalign’s technological updates, including its
auxiliaries, such as miniscrew anchorage, elas- G4 and G7 optimized maxillary lateral attach-
tics, and partial fixed appliances, have been ments, which were respectively introduced in late
shown to address current limitations in clear 2011 and late 2016 and specifically target maxil-
aligner therapy and improve the accuracy of lary lateral extrusion [2]. Clinically, we have
problematic movements [6]. observed that the incorporation of the optimized
In this chapter, we focus on a number of tradi- lateral attachments have enhanced predictability
tionally problematic and complex movements in in correcting displaced lateral incisors, especially
clear aligner therapy, including control of maxil- when they require the difficult movements of
lary lateral incisors, uprighting, intrusion, and extrusion and derotation. In cases where lateral
extrusion. We discuss the challenges involved in incisors require significant derotation in addition
planning and executing these movements, as well to intrusion or extrusion, the use of an optimized
as solutions to improving their accuracy and G4 or G7 attachment is recommended for the
achieving successful and predicted outcomes. accuracy of movement (Fig. 4.1). This is in agree-
ment with the findings of a number of clinicians,
who have recommended the use of attachments
he Challenges of Controlling
T for improved rotational control [7].
Maxillary Lateral Incisors However, we note that despite improvement in
maxillary lateral control from earlier generations
Invisalign G4 and G7 Attachments of clear aligners, the accuracy of their move-
ments remains low, at 53.7% for extrusion and
Invisalign’s G4 and G7 generation features 48.7% for distal rotation, relative to movements
included modifications designed for improving such as labial tipping (69.9%) [2]. Consequently,
the predictability of maxillary lateral incisor extreme rotations, such as those >15° or signifi-
movement. Specifically, the G4 “SmartTrack” cant extrusion, may require further supplementa-
features are triggered to automatically incorpo- tion, in addition to the use of the G4 and G7
rate optimized multiplane attachments on maxil- optimized attachments, to achieve desired out-
lary laterals undergoing extrusive movements in comes for maxillary lateral movement.
addition to rotation and/or crown tipping in the Another complication in attachment design
mesiodistal dimension. The G7 generation fea- for maxillary lateral incisors arises when they
tures, which claimed to enhance detailing and require significant intrusion, which has been
finishing for clinicians, further refined maxillary shown to be low in accuracy. Intrusive move-
lateral control through the second generation of ments are best performed without attachments. It
optimized multiplane attachments to improve is recommended that the clinician omit an attach-
tracking when rotation is combined with either ment on the lateral incisor if it requires signifi-
intrusion or extrusion. The G7 generation fea- cant intrusion (without the need for extensive
tures also introduced optimized support attach- rotational or mesiodistal tipping movements) for
ments on maxillary laterals to maintain tracking improved predictability.
Fig. 4.1 G7 optimized attachments have been placed on optimized G7 attachments for maxillary lateral incisor
the maxillary lateral incisors to enhance the predictability derotation, especially for significant rotations, such as
of derotation. When possible, the provider should request those >15°
In early 2021, Invisalign introduced its G8 especially when the tooth was initially signifi-
generation features, one of which is designed for cantly displaced, whether requiring rotation >15°
the enhancement of incisor intrusion through or in linguoversion. If the necessary derotation of
“aligner activation,” which refers to the specific maxillary lateral incisor is minor— <15°—then,
contouring of the aligner to deliver optimal forces the clinician may be able to modify the aligner
and minimize undesirable movements through geometry in order to supplement the forces sup-
improved control over location, direction, and plied by the aligner. In such cases, hand instru-
amount of force (Fig. 4.2) [8]. The efficacy of the ments can be employed to produce additional
G8 features has not been clinically evaluated. forces in either the first or second order. For
The G8 modifications focus only on optimizing example, if the maxillary lateral incisor is mesi-
intrusive movements for the anterior teeth and ally rotated and requires distal rotation, then the
not extrusion or movements in the other orders clinician can place dimples with a dimple plier on
(though Invisalign claims the modifications will the mesiolingual and distolabial surfaces of the
also enhance posterior arch expansion with opti- aligner to create a rotational couple in the distal
mized expansion support attachments). direction. The patient can wear the modified
aligner for an extended period of time, such as
4–6 weeks, to allow for expression of the supple-
lteration in Aligner Geometry
A mentary forces. It is also prudent for the clinician
for Enhancement of Tooth Movement to verify that there is adequate interproximal
space for derotation. Research findings have
Often, cases arise when maxillary lateral incisors shown that teeth which received interproximal
fail to track toward the end of a course of aligners, reduction, when compared to those that did not
sor and the two teeth immediately adjacent. A

light NiTi wire should be able to fully align the
lateral incisor in 4–8 weeks (Fig. 4.3). The clini-
cian should be mindful to cut the aligner so that it
does not interfere with the fixed appliances, while
it still sufficiently encapsulates the adjacent teeth
to retain their positions.
uxiliaries for Enhancement of Tooth

A
Movement
Poor tracking of maxillary lateral incisors can

also be improved with the use of alternative aux-
iliaries, including buttons and elastics. Notably,
these auxiliaries can be incorporated when max-
illary lateral incisors do not achieve planned
extrusive movements. For example, if a maxillary
Fig. 4.2 Invisalign G8 generation modifications include lateral incisor begins to track poorly in the inciso-
“aligner activation” for supposedly improved control over gingival dimension and fails to extrude, the clini-
intrusive forces to the maxillary and mandibular anterior cian can bond a button on the lateral incisor for a
teeth. Other features include optimized support attach-
ments designed for more bodily posterior expansion vertical elastic to be worn to the opposing canine
for a supplementary extrusive force (Fig. 4.4).
The elastic can be extended from the button on
receive interproximal reduction, show greater the problematic lateral incisor to either another
accuracy with rotation [9]. (We will further dis- button on the opposing canine or a precision cut
cuss detailing and finishing in Chap. 11). If dis- on the aligner respective to the canine. This sup-
crepancies in maxillary lateral incisor position are plementary extrusive force can be applied until
significant, other measures, such as the use of the lateral adequately tracks or until the comple-
alternative auxiliaries or a course of refinement, tion of the course of aligners (or it can be applied
are more adequate. on a final aligner for extended wear to improve
tooth position).
Combination Treatment with Fixed

Appliances Overcorrection for Improved
Predictability of Maxillary Lateral
In circumstances when maxillary lateral incisors Incisor Movement
cannot be fully derotated whether through altera-
tions in aligner geometry or courses of refine- Overcorrection for improved predictability of
ment, a short period of partial fixed appliances tooth movement has been recommended by a
can be helpful to fully correct discrepancies in number of studies [3]. This method can be applied
tooth position. Partial fixed appliances can be to the planned movements of maxillary lateral
placed on the problematic maxillary lateral inci- incisors in both first and second orders. For
example, for a maxillary lateral incisor that ments. However, the overcorrections should be
requires significant labialization, the clinician applied judiciously so they do not result in
can exaggerate the amount of labialization so that adverse effects for the occlusion, such as heavy
on the Clincheck, the lateral incisor will finish anterior interferences, anterior open bites, or
slightly labial to its ideal position relative to the undesirable changes in overjet and overbite.
adjacent teeth. Similarly, for a high maxillary lat-
eral incisor requiring significant extrusion, such
as >2.5 mm, the clinician can over-engineer the orque Control for Maxillary Lateral
T
amount of extrusion on the tooth in the Clincheck Incisors
in order to compensate for the difficulty of the
movement. This method can also be useful for For severely lingually displaced maxillary lat-
addressing severe rotations in maxillary lateral eral incisors, significant labial root torque is
incisors, whose rotational movements can be often necessary for ideal tooth positioning. As
exaggerated to achieve more ideal outcomes. It is discussed in Chap. 1, most current softwares,
difficult to recommend the precise margin for from Invisalign to 3M to Suresmile, lack ade-
overcorrection of difficult lateral incisor move- quate controls for labial root torque. The
Fig. 4.3 Severe rotations of maxillary lateral incisors of the right maxillary lateral incisor. A short course of par-
may require auxiliary fixed appliances for complete dero- tial fixed appliances completely resolved the rotation
tation. For patient J.L., an initial and single refinement without the need for another refinement course
course of aligners did not completely resolve the rotation

Fig. 4.4 The placement of a button on maxillary lateral The button can be bonded toward the end of the initial
incisors allows for the application of a supplementary course of aligners or following the initial course to mini-
extrusive force to achieve desired final tooth positions. mize the duration of refinement
Invisalign software currently does not allow for estorative Solutions for Maxillary
R
power ridges on lingual surfaces, nor does it Lateral Incisors
allow for free placement of power ridges by the
clinician. As a result, supplementary labial root Maxillary lateral incisors are one of the most
torque may be programmed through over-engi- commonly congenitally misshapen teeth and the
neering in the Clincheck for lateral incisors overall prevalence of peg-shaped maxillary per-
requiring significant correction. Alternatively, if manent lateral incisors has been recently reported
the lateral incisor fails to track in the third order to be 1.8% [10]. In addition, 55.5% of individuals
during a course of aligners, supplementary with unilateral peg-shaped maxillary lateral inci-
labial root torque can be incorporated with the sors exhibit contralateral maxillary lateral incisor
use of hand instruments, in the method of a hypodontia [10]. Therefore, it is likely the clini-
power ridge on the linguogingival surface and cian will encounter malformed maxillary lateral
pressure point on the labio-incisal surface to incisors that require restorative solutions for opti-
produce a torquing couple (see Chap. 1 for more mal occlusion and esthetics. Future restorations
detailed discussion). can be planned during Clincheck development
with the same principles as those applied to fixed treatment planning (Fig. 4.6). Circumstances
appliances [11]. For a peg-shaped maxillary lat- may arise when the opening of space for lateral
eral incisor requiring a future veneer, crown, or incisor restorations are not indicated, such as
composite build-up, the clinician can position the when the opening of the space for an ideally sized
final position of the tooth with adequate space for lateral would result in an excessive overjet. In
restoration to ideal dimensions (Fig. 4.5). As with these cases, the clinician may have to close the
fixed appliances, it is recommended that the spaces adjacent to the maxillary lateral incisor,
space allocated for the restoration is determined compromise an ideal Class I occlusal relation-
in an interdisciplinary fashion with the restor- ship, and finish in an end-on Class II relationship
ative dentist. on the side with the abnormally small maxillary
lateral incisor (Fig. 4.7).
Bolton Discrepancies
Missing Maxillary Lateral Incisors
Abnormally small maxillary lateral incisors may
likely result in Bolton maxillary deficiencies. The There are situations when mesioangulated
Bolton analysis tool in the Clincheck can be use- impacted maxillary canines damage the roots of
ful in verifying tooth size discrepancies during the adjacent maxillary lateral incisors to such an
Fig. 4.5 Abnormally small maxillary lateral incisors clinician should treatment plan in an interdisciplinary
should be adequately positioned for future restorative fashion with the restorative dentist for optimal esthetics
treatment, whether in the form of veneers or crowns. The
Fig. 4.6 The Bolton analysis feature is a tool during ative treatment. It is also useful for planning the correction
treatment planning that can assist in ideally positioning of sagittal occlusal relationships, which may involve a
the maxillary lateral incisors. In certain circumstances, the degree of compromise when Bolton discrepancies exist
lateral incisor may need to be positioned for future restor-
Fig. 4.7 A Bolton maxillary deficiency resulted in Class II end on occlusion on the right side
extent that extraction of the lateral is indicated. In of the substituted canine should be slightly inci-
these cases, the clinician can plan in the software sal to that of the central incisor. For optimal
for either complete closure of the maxillary lat- esthetics, after orthodontic treatment, the patient
eral space with canine substitution or mainte- may require crown lengthening for ideal gingival
nance of the space for a future implant (Fig. 4.8). contours and restorative treatment in the form of
Space closure is best when the maxillary incisors composite bonding or porcelain veneers.
are protruded and the posterior teeth are in Class
II relationships so that spaces can be reciprocally
closed with protraction of the posterior teeth and Root Uprighting
retraction of the incisors [12]. The substituted
canine should be positioned as esthetically as lements of Successful Uprighting—
E
possible with consideration of the canine’s shape, The Virtual Gable Bend
color, and gingival level. Ideally, a substituted
canine should be of a similar shade to the central Studies have shown that clear aligners are not as
incisor, is shaped narrow at the cemento-enamel successful in root control and alignment as com-
junction both labiolingually and mesiodistally, pared to fixed labial appliances [14]. Essential
and demonstrates a flat emergence profile [13]. elements for the successful uprighting of roots
To simulate a lateral incisor, the gingival margin include:
Root Uprighting 77
Fig. 4.8 Patient J.L. received two phases of orthodontic resorbing the root of the left maxillary lateral incisor.
treatment. Phase I comprised of rapid maxillary expan- Because of the damage to the left maxillary lateral incisor,
sion and high-pull headgear. Following phase I, it was the tooth was extracted and a canine substitution for the
observed that the erupting left maxillary canine was maxillary lateral incisor planned
1. The judicious prescription of virtual gable lements of Successful Uprighting—

E
bends. Attachment Design
2. Optimal attachment design.
The judicious use of attachments on the teeth to
The virtual gable bend (VGB) allows for be uprighted is also critical for successful out-
simultaneous root movement during crown comes. In the case of uprighting canines or pre-
movement. Though the Clincheck will incorpo- molars, it is recommended that the clinician
rate root movement for the uprighting of tipped either maintain optimized root control attach-
teeth, the clinician frequently has to prescribe a ments or prescribe them if absent. However, the
virtual gable bend to supplement uprighting for software will often not allow for the placement of
achieving the desired amount of root movement optimized root attachments. Consequently, the
(Fig. 4.9). The VGB will both increase the clinician should design adequately oriented con-
amount of root movement and decelerate the ventional attachments to supplement the upright-
velocity of movement by altering the staging and ing movement. For example, if a mandibular left
increasing the total number of aligners. first second premolar is mesially tipped, then a
Fig. 4.9 In this case with extractions of maxillary first maxillary second premolar and left first molar. The addi-
premolars, the left maxillary second premolar and left tion will increase the total number of active aligners but
maxillary first molar tipped undesirably during space clo- will incorporate greater amount of root movement to the
sure. These were uprighted with the addition of a virtual adjacent teeth
gable bend between the left maxillary canine and the left
a b
c d
Fig. 4.10 For patient R. W. (a, b), both the right maxil- the left mandibular second molar needed to be uprighted
lary first molar and the right maxillary first premolar had to create adequate space for the left mandibular first
to be uprighted to create adequate space for a maxillary molar. An attachment was designed with the bevel (active
second premolar implant. Both attachments were designed surface) facing mesially to supplement a distalizing force.
with bevels directed mesially to supplement a distal force The attachment was also directly slightly occlusally to
for mesial movement of the roots. For patient J. X. (c, d), enhance intrusion of the molar
vertical attachment can be placed with its bevel mandibular left second premolar, a vertical
directed mesially. This attachment will supple- attachment with its bevel oriented mesially can
ment a distal force to tip the crown distally and be placed to supplement a distal force to the
the root mesially. A similar concept can be crown (Fig. 4.10).
applied to tipped molars. For a mandibular left Theoretically, the uprighting of a molar would
first molar tipped mesially because of a missing be ideally supplemented with the use of an attach-
Root Uprighting 79
tulous site. For example, if a first mandibular left

molar, adjacent to a missing mandibular left second
premolar, were to be uprighted, then the clinician
should ensure the aligner material fully encapsu-
lates the mesial surface of the first molar. This can
be achieved by requesting a half-sized pontic for
the mandibular left second premolar during the ini-
tial setup for the treatment simulation (a full-sized
pontic would prevent complete encapsulation of
the first molar to be uprighted) (Fig. 4.13).
Fig. 4.11 The ideal attachment configuration for the

Auxiliaries for Uprighting
uprighting of a mesially tipped molar would be one that
would allow for the delivery of a couple, in the fashion of In a similar fashion to achieving difficult maxil-
optimized root control attachments for canines and lary lateral incisor movements, uprighting move-
premolars
ments can be supplemented with the use of
auxiliaries, whether in the form of partial fixed
ment that allowed for a couple, in the fashion of appliances with sectional mechanics, elastics, or
the premolar optimized root control attachments temporary anchorage devices (TADs). For exam-
(Fig. 4.11). At present, these coupled attachments ple, for a mesially tipped mandibular right first
are not available for molars. Instead, the clinician molar, brackets can be placed on the adjacent
must resort to adjusting the vertical beveled mandibular right second molar and mandibular
attachments for the proper force systems. right second premolar and aligned with light
wires during clear aligner therapy (Fig. 4.14).
Similarly, elastics can be worn from a precision
Treatment Duration cut of the opposing molar in the maxillary arch
for extrusive movement. Alternatively, a TAD
For difficult uprighting movements, the incorpo- can be placed in the buccal shelf mesial to the
ration of the virtual gable bend requires an tooth to be uprighted; a mesializing force can
increase in the total number of aligners relative to then be applied to the tooth from the TAD to a
the same course of aligners without a virtual power arm extending from a band.
gable bend (Fig. 4.12). The clinician should
appropriately stage the uprighting movement in
accordance with current Invisalign software rec- Uprighting in Extraction Cases
ommendations of 2° tipping/aligner [15]. It has
been shown that maintaining forces of less than In extraction cases, the teeth adjacent to extrac-
2° tipping/aligner is most ideal for delivering tion spaces often exhibit greater mesiodistal tip-
optimal forces to the PDL, in accordance with the ping than predicted. For example, in patients
“optimal force paradigm” of biological tooth receiving maxillary first premolar extractions,
movement [16, 17]. maxillary second premolars and maxillary first
molars typically demonstrate greater mesial tip-
ping than desired (Fig. 4.15) [4]. As a result, the
Coverage of Aligner Material clinician often has to upright tipped premolars
and molars adjacent to extraction spaces (we will
It is important for successful uprighting that the further discuss finishing for extraction therapy in
aligner material completely embrace the tooth to be Chap. 9). The aforementioned principles for
moved, especially in that area adjacent to an eden- uprighting, including the use of either root con-
Fig. 4.12 For patient Y. C., the incorporation of a virtual Orthodontic treatment with an initial and single refine-
gable bend between the right mandibular second premolar ment course created an ideal space for a premolar-sized
and right mandibular first molar allowed for uprighting of implant restoration. After orthodontic treatment, a
both roots. The increase in amount of root movement with premolar-
sized implant restoration was placed in the
the virtual gable bend also increased the total number of molar’s edentulous space
aligners in which the two teeth would be moved to 26.
Root Uprighting 81


Root Uprighting 83

trol attachments or properly oriented vertically

beveled attachments, should also be applied to
teeth that have tipped undesirably during extrac-
tion therapy.
Uprighting in Class II Treatment
In the treatment of Class II malocclusions, maxil-

lary canines with crowns that are excessively
tipped to the mesial can contribute to posterior
end-on Class II relationships. Therefore, it is
essential for Class II correction that the maxillary
Fig. 4.13 A half-sized pontic adjacent to the premolar
that requires uprighting allows for full encapsulation of
canines be uprighted. This movement can be sup-
the tooth with the aligner and more predictable plemented with G4 optimized root control attach-
uprighting ments and Class II elastics (Fig. 4.16a, b).
Fig. 4.14 Partial fixed appliances can be combined with molars to upright the impacted second molars. Vertical
clear aligners for complex uprighting movements. In this elastics were also worn from lingual buttons on the maxil-
case, braces were bonded on the second mandibular pre- lary second molars to the mandibular second molars to
molars, mandibular first molars, and mandibular second supplement uprighting
Simplifying Complex Movements 85
Fig. 4.15 Patient C. Y. was treated with a four first pre- mandibular posterior teeth adjacent to extraction spaces
molars extraction pattern to decrowd maxillary and man- tipped greater than the amount programmed. These pre-
dibular arches and reduce their bimaxillary protrusion. molars and molars will have to be uprighted either with
After the initial course of aligners, both maxillary and auxiliaries or an additional course of refinement
Similarly, in the treatment of Class II division to simulated outcomes, relative to movements

II malocclusions, inadequately torqued maxillary such as lingual tipping.
incisors can result in mesio-occlusion [18]. The The clinician can more predictably plan for
incorporation of power ridges has been shown to successful outcomes in these movements through
increase the predictability of incisor torque and the judicious use of attachments, the incorpora-
therefore would be beneficial in the uprighting of tion of compensatory mechanics, such as over-
retroclined maxillary incisors [19]. Conversely, engineering and virtual gable bends, and
the uprighting of proclined maxillary incisors is supplementation with auxiliaries in the form of
also critical for successful management of Class partial fixed appliances, TADs, and elastics. The
II division I malocclusions. The clinician should positioning of maxillary lateral incisors for opti-
be cautious not to over-retract the maxillary inci- mal esthetics and function also depends on a
sors. Torque can be controlled with the judicious variety of factors, such as tooth size discrepancy,
incorporation of power ridges, avoiding overuse tooth shape, and gingival architecture, which
of Class II elastics, and sound planning for the should be considered in the treatment planning
degree of incisor retraction. phase and Clincheck development.
Tooth uprighting is not only limited to tipped
premolars and molars adjacent to edentulous
Simplifying Complex Movements spaces but also to retroclined maxillary incisors,
mesially tipped canines, and teeth that have
The control of maxillary lateral incisors and tooth tipped as a result of extraction therapy. The
uprighting remain challenges for clear aligner uprighting of tipped canines and lingually
therapy. Recent clinical trials show that they inclined maxillary incisors allows for sagittal
remain problematic despite the technological correction of Class II occlusal relationships and
improvements of the last decade. Both move- is a cornerstone for the successful treatment of
ments consistently show low accuracy compared Class II malocclusions.
Fig. 4.16 (a, b) The two cases above demonstrate the proper crown angulations of the maxillary canines is criti-
uprighting of the maxillary left and right canines allows cal for correcting the Class II relationships in the posterior
for uprighting of the posterior teeth. The achievement of occlusion
References 87
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of attachments and interproximal reduction on the
accuracy of canine rotation with Invisalign. A pro-
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spective clinical study. Angle Orthod. 2008;78:682–7.
B. How well does Invisalign work? A prospective
10. Hua F, He H, Ngan P, Bouzid W. Prevalence of
clinical study evaluating the efficacy of tooth move-
peg-shaped maxillary permanent lateral incisors:
ment with Invisalign. Am J Orthod Dentofac Orthop.
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2013;144(1):97–109.
2. Haouili N, Kravitz ND, Vaid NR, Ferguson DJ,
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Makki L. Has Invisalign improved? A prospec-
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Esthet Restor Dent. 2002;14(4):217–24.
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2020;158(3):420–5.
orthodontics. 5th ed. St. Louis: Elsevier; 2013. p. 455.
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13. Kokich VO Jr, Kinzer GA. Managing congenitally
missing lateral incisors. Part I: canine substitution. J
Esthet Restor Dent. 2005;17(1):5–10.
2018;19(1):37.
14. Pavoni C, Lione R, Laganà PC. Self-ligating versus
4. Dai FF, Xu TM, Shu G. Comparison of achieved
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and predicted tooth movement of maxillary first
Stomatol (Roma). 2011;2(1–2):23–7.
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7. Djeu G, Shelton C, Maganzini A. Outcome assess-
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ment of Invisalign and traditional orthodontic
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Interproximal Reduction
5
Contents
Interproximal Reduction and Clear Aligner Therapy 89
The Indications of IPR 90
IPR Technique 96
Considerations when Planning IPR 97
Reflections on IPR in Clear Aligner Therapy 99
References 99
I nterproximal Reduction and Clear IPR was first employed as a means for the
Aligner Therapy resolution of minor anterior dental crowding, but
its use has been expanded to a variety of applica-
Interproximal reduction (IPR) has become an tions. It is now considered a viable alternative to
essential method of space creation and arch extraction therapy, as the clinician can calculate
development in clear aligner therapy. IPR encom- the removal of tooth structure to generate the spe-
passes the reduction and anatomical recontouring cific amount of space necessary for decrowding a
of enamel within the interproximal regions of dental arch [3]. IPR also functions as an impor-
adjacent teeth. It was first employed as a space- tant tool in the correction of interocclusal dis-
gaining procedure by Ballard, who used inter- crepancies in Class II and Class III malocclusions.
proximal reduction for decrowding anterior teeth It can diminish the effects of Bolton tooth size
in 1944 [1]. The method was further developed discrepancies in both the anterior region and full
by practitioners such as Hudson, Paskow, Jack arches [4]. Asymmetric IPR can contribute to the
Sheridan with his air-rotor stripping technique, resolution of midline deviations. IPR can also
Don Tuverson, and Bjorn Zachrisson, who rec- normalize proclined incisors, while in other
ommended flexible diamond discs [2]. In con- cases, it can resolve dental crowding while main-
temporary orthodontic practice, the techniques taining desirable incisor inclinations and the
for IPR have evolved to include the use of manual intercanine distance within dental arches. The
perforated metal strips, IPR burs, rotating discs, method has been shown to reduce the appearance
and reciprocating strips mounted on a contra- of black triangles by broadening the contact areas
angle handpiece.

https://doi.org/10.1007/978-3-030-92810-0_5
90 5 Interproximal Reduction
Fig. 5.1 In borderline extraction cases, carefully planned IPR can resolve severe crowding while minimizing undesired
expansion of the mandibular intercanine width and maintaining normal mandibular incisor inclinations
and moving them gingivally to minimize gingival judicious planning of IPR reduces the amount of
embrasures. buccal expansion and proclination of the incisors
The judicious planning of IPR is critical for needed for decrowding a dental arch and there-
successful outcomes in clear aligner therapy. The fore diminishes the risk of periodontal problems
adequate incorporation of IPR is essential for and stability issues associated with these move-
achieving difficult movements, such as canine ments [5]. Current software setups, whether from
derotation, predictable treatment of Class II and Invisalign, 3M, Suresmile, or U-Lab, allow the
Class III discrepancies, and decrowding in non- clinician to determine at which site to perform
extraction cases, particularly those that lie in the the IPR, the amount of reduction, and the timing
borderline between extraction and non-extraction. of the IPR during the course of treatment [6].
The precise execution of the planned IPR is The incorporation of IPR can also reduce the
also essential for sequential fitting of the aligners likelihood of extraction therapy, particularly in
and the achievement of projected tooth move- borderline cases (Fig. 5.1). Arches requiring
ments [3]. Studies have shown that proper instru- greater than 8 mm of space would be a contrain-
mentation and technique are important to dication for IPR [2]. In borderline cases, the cli-
performing precise IPR, as well as minimizing nician can digitally simulate extraction and
unnecessary round tripping of the teeth and non-extraction treatment plans for comparison
adverse sequelae, including root resorption. prior to committing to a course of therapy.
In this chapter, we discuss the indications of IPR
in the context of clear aligner therapy, ranging from
decrowding dental arches to the correction of sagit- reatment of Class II and Class III
T
tal discrepancies to midline coordination. Malocclusions
Afterwards, we elaborate on techniques for per-
forming precise IPR and conclude this chapter with One of the modalities for the treatment of Class II
considerations when planning IPR in the treatment malocclusions is the distalization of the upper
of both simple and complex malocclusions. arch. Rossini et al. have shown that maxillary
molar distalization was highly predictable with
an 88% accuracy when distalization of 1.5 mm
The Indications of IPR was prescribed (though these results have recently
been disputed by a 2021 study on the efficacy of
Decrowding Class II malocclusion correction with clear
aligner therapy) [7, 8].The selective incorpora-
One of the primary indications of IPR is the reso- tion of IPR can improve the predictability of
lution of crowding. In non-extraction cases, the Class II correction by supplementing the distal-
izing movement, especially when the forecasted that have suggested reduction of enamel to a
translation is not achieved during treatment. maximum of 0.3 mm per contact point for maxil-
Specifically, in a patient where distalization is lary incisors, 0.2 mm for mandibular incisors,
indicated, the clinician can plan for 0.5 mm of and 0.6 mm for premolars and molars [2]. This
IPR in the posterior segments (distal to the maxil- procedure generates a cumulative 4.5 mm from
lary canines) and 0.3 mm of IPR between the the IPR and 1–2 mm of maxillary distalization on
anterior teeth (extending from the mesial contact each side for the correction of overjet and Class II
of the maxillary canine to the contralateral mesial sagittal relationships (Fig. 5.2).
contact of the maxillary canine). This protocol is In certain cases, significant distalization is
in accordance with clinical recommendations necessary, such as translations of greater than
Fig. 5.2 About 1–2 mm of distalization was planned for and left maxillary second premolar and left first molar.
the left maxillary premolars and left maxillary molars. This protocol allowed for the correction of the left canine
0.5 mm of IPR was performed for the interproximal con- relationship to Class I, normalization of the maxillary
tacts between the left maxillary canine and left maxillary incisors, and the idealization of the overjet
first premolar, left maxillary first and second premolars,
Fig. 5.3 This case was treated with a combination of segmental distalization and posterior IPR to correct the increased
overjet and the end-on Class II molar and canine relationships. The treatment duration was 13 months
2 mm. In treatment planning these movements, dibular canine to the contralateral mesial contact
aggressive posterior IPR can supplement seg- of the mandibular canine) and 0.5 mm in the pos-
mental distalization (movement of the segment terior segments (distal to the mandibular canines).
collectively) in place of sequential distalization Certain Class III malocclusions with severe
(distal movement of each posterior tooth, indi- crowding or more severe skeletal discrepancies
vidually). The former approach can decrease receiving nonsurgical compensatory treatment
treatment time and increase the predictability of may require extraction therapy in addition to IPR
the distal movement of the maxillary arch to achieve successful outcomes. For example, for
(Fig. 5.3). a patient with moderate mandibular crowding in
IPR can also be incorporated for improving addition to a moderate reverse overjet, a viable
the predictability of treatment in Class III maloc- treatment may be the extraction of a crowded out
clusions. In cases where non-extraction is indi- mandibular incisor and maxillary IPR for
cated, IPR can be employed to supplement decrowding and achievement of ideal overjet
retraction of the mandibular premolars and the (Fig. 5.4). Orthodontic camouflage of Class III
anterior teeth. For Class III malocclusions of malocclusions is more likely to be successful in
mild to moderate severity, the clinician can adjust adult patients with an average or short facial pat-
according to space required by an IPR protocol of tern, mild sagittal jaw discrepancy, crowding
0.2 mm between the mandibular anterior teeth <4–6 mm, normal soft tissue features, and no
(extending from the mesial contact of the man- transverse skeletal discrepancy [9].
Fig. 5.4 In patients with Class III malocclusions of mild illary and mandibular arches. The maxillary IPR will
to moderate severity, mandibular crowding, and reverse allow for retraction of the maxillary incisors for the
overjet, the extraction of one mandibular incisor can be achievement of ideal overjet
combined with maxillary IPR for decrowding of the max-
Tooth Size Discrepancies [10]. IPR can address Bolton discrepancies,

through the removal of enamel in either the
Studies have demonstrated that 20–30% of maxillary or mandibular arches to compensate
studied populations present with anterior for maxillary or mandibular excess, respec-
Bolton discrepancies, while 5–14% of sample tively (Fig. 5.5). As previously discussed, the
populations demonstrate full arch discrepancies Bolton index can be instantly obtained in the
Fig. 5.5 In Patient H. Z., a Bolton maxillary deficiency closure of existing maxillary spaces through retraction of
was addressed with mandibular IPR. Adequate mandibu- the mandibular incisors, and the creation of ideal overjet
lar IPR allowed for decrowding of the mandibular arch,
Clincheck setup or through most types of cast Midline Coordination

analysis software. In cases where anterior teeth
are abnormally large (macrodontia), the clini- Mild midline discrepancies can be resolved with
cian may consider more aggressive IPR to asymmetric IPR on the side toward which the
reduce the size discrepancy between the maxil- deviated midline must be translated (Fig. 5.6).
lary and mandibular anterior regions and to This translation can be supplemented with asym-
achieve more ideal overjet and overbite [2]. metric intermaxillary elastics, a method that has
been effectively employed with fixed appliances
in nonsurgical treatments of mild asymmetries
Incisor Uprighting [12]. Precision cuts can be incorporated on the
aligner for either unilateral Class II or Class III
IPR is critical for normalizing the inclination of elastics or cross-midline elastics.
proclined incisors, whether in Class II division 1
malocclusions or cases of bimaxillary protrusion.
The normalization can be achieved with an IPR Gingival Black Triangles
protocol similar to that employed for Class II cor-
rection through maxillary arch distalization. For Studies have shown there are multiple factors that
either maxillary or mandibular incisors, the clini- comprise the etiology of black triangles, includ-
cian can perform 0.3 mm of IPR per contact in ing the interproximal space between teeth, the
the anterior region and incorporate additional distance between the bone crest and the contact
0.5 mm per contact of posterior IPR, as necessary point between two adjacent teeth, gingival bio-
for incisor retraction. The uprighting of incisors type, patient age, periodontal disease, root diver-
can be supplemented by intermaxillary elastics gence, and tooth morphology [13]. Orthodontic
(Class II elastics for uprighting the maxillary therapy has been demonstrated to reduce gingival
incisors and Class III elastics for uprighting the black triangles through a number of applications.
mandibular incisors). Clear aligners tend to per- Orthodontic movement can close interdental con-
form buccal-lingual tipping with high accuracy tacts, reduce the distance between the contact
relative to other movements [11]. However, it is point and the crest of bone, and reduce the likeli-
important for the clinician to avoid over-retraction hood of a black triangle. Paralleling converging
of incisors by avoiding excessive IPR and roots has also been shown to be beneficial in
regularly monitoring the use of intermaxillary restoring the interdental papillae [14]. IPR can
elastics. reduce gingival black triangles by reshaping the
Fig. 5.6 Asymmetric IPR can accurately correct midline mandibular midline to the left. Maxillary IPR also allowed
discrepancies. In the above case, asymmetric IPR in the for normalization of the maxillary incisors and overjet
mandibular left quadrant allowed for the translation of the
Fig. 5.7 In this case, mandibular anterior IPR was performed to create wider interdental contacts, which allowed for
repositioning of contacts more gingivally. This approach can minimize the appearance of gingival black triangles
proximal enamel for broader interdental contacts dency of canines to be frequently in difficult to
and repositioning the contact more gingivally access positions, either in labioversion, distal
(Fig. 5.7). rotation, or within tight contact areas.
The accuracy of performed IPR is multifacto-
rial, associated with tooth-related factors, such as
Retention enamel hardness, tooth morphology, and tooth
position, as well as operator-related factors, such
There is some evidence that suggests IPR as a as technique employed, the pressure exerted dur-
means to enhance retention and stability following the procedure, the hardness and particle size
ing orthodontic treatment [15]. The improvement of the abrasive, the time taken for the procedure,
in stability may be associated with the broadening clinician experience, and accuracy of the space
of contact point areas and reduction in the analysis [17]. In particular, studies have sug-
amounts of buccal expansion. gested the type of technique can influence the
accuracy of IPR [16]. At present, there are four
common methods of performing IPR [1]:
IPR Technique
1. The air-rotor stripping method with tungsten-
The accurate execution of the planned IPR is carbide burs or diamond burs.
critical for achieving desired tooth movements 2. The air-rotor stripping method with diamond
and successful clinical outcomes. Recent studies coated strips (Ortho-strips), usually mounted
on the use of IPR in clear aligner therapy suggest with a handpiece.
that the amount of IPR performed frequently did 3. Diamond-coated disks mounted with a hand-
not correspond to the amount programmed [5]. In piece or contra-angle.
most cases, the amount of enamel removed was 4. Handheld abrasive metal strips used
less than that planned [5]. A recent study on this manually.
issue found that there was a greater discrepancy
between planned and performed IPR for distal Research has shown handheld abrasive metal
surfaces compared to that of mesial surfaces, strips (method 4) can be laborious, impractical,
while among individual teeth, the mandibular and time-consuming, especially for contact
canines showed the greatest discrepancy between points between the posterior teeth. Recent studies
planned and performed IPR [16]. The latter dis- have suggested that the discrepancy between per-
crepancy was attributed by the authors to the ten- formed IPR and predicted IPR was greater for the
Considerations when Planning IPR 97
manual strips technique when compared to that performing IPR, whether in the form of varnish,
of either burs or handpiece-operated diamond- mouthwash, or solution, such as Gel-Kam, all of
coated strips [16]. This result may be attributed to which can function as a barrier against the demin-
the laboriousness of the manual method. Also, eralization of reduced enamel [18].
the forcing of the abrasive strips into interproxi-
mal regions can displace teeth temporarily into
periodontal spaces leading to the overestimation Considerations when Planning IPR
of the amount of enamel removed.
The use of burs has gained widespread accep- Round Tripping and IPR
tance because of their advantages of greater preci-
sion and painlessness. Burs do have the A common method of incorporating IPR into a
disadvantage of leaving rough interproximal sur- clear aligner treatment plan is programming
faces after enamel reduction. These surfaces can be additional movements and aligners primarily to
subsequently polished with either the handheld improve accessibility to obstructed contact areas.
abrasive strip or a thin diamond-coated strip. In such cases, these additional movements con-
Diamond discs, when operated on a handpiece, can stitute round tripping because they have to be
be dangerous intraorally because of their proximity reversed later on in treatment. A recent study
and risk to the patient’s lips and cheeks. Discs can showed that though round tripping slightly
also be unpredictable in their removal of enamel. improved the accuracy of IPR compared to accu-
They have the capability of creating ledges, as well racy with lack of round tripping, the difference
as deep cuts into the enamel, resulting in possible was not statistically significant [16]. Round trip-
complications, such as increased plaque retention, ping can lead to increased treatment times and
caries risk, and risk of periodontal disease. unnecessary additional movements, increasing
Accurate and safe IPR can be achieved the risk for root resorption. It is prudent that the
through the use of the Ortho-strips in a sequential clinician minimize round tripping merely for the
fashion for anterior segments and the air-rotor sake of performing more accurate IPR. The use
stripping method with burs in posterior segments. of diamond burs and Ortho-strips, which afford a
For an anterior interproximal area, the contact degree of flexibility, more readily allow for
can be broken with a 0.1 mm thick Ortho-strip. enamel reduction in obstructed areas and the
Subsequently, the clinician can sequentially minimization of round tripping for the sake of
remove enamel with a 0.2 mm thick strip, a IPR. A viable alternative to round tripping is the
0.3 mm strip, until the desired amount has been use of separators for extremely tight or over-
achieved. In the posterior segment, a 0.5 mm dia- lapped contacts prior to IPR, which was advo-
mond bur can be used for accurate enamel reduc- cated by early users of IPR, such as Bjorn
tion. For both anterior and posterior contacts, a Zachrisson [19]. The clinician can place a separa-
finishing Ortho-strip can be used for smoothing tor into the tight interproximal space 1–2 weeks
rough interproximal surfaces. Also, an IPR gauge prior to the IPR appointment for increased acces-
should be used to verify the amount of enamel sibility and greater accuracy.
removed in each site. Naturally, it is less detri-
mental to perform less IPR than prescribed com-
pared to more than prescribed because if Timing of IPR
additional IPR is needed, it can be prescribed in a
refinement stage. The gauge has been shown to The visit in which the clinician performs the IPR
control the amount of IPR performed and improve should be considered one of the most critical dur-
accuracy (Fig. 5.8). Bitewing radiographs can be ing the course of treatment because it is a signifi-
taken following IPR to assess for ledges or areas cant factor in the accuracy of the planned tooth
of significant roughness. Lastly, the clinician movements and the sequential fitting of the align-
should provide a type of fluoride treatment after ers. Ideally, all of the IPR should be planned on a
a b
c d
Fig. 5.8 (a) IPR gauges can be used to verify that the The resulting interproximal surfaces can be smoothened
desired amount of IPR has been achieved. Their use has either with handheld abrasive metal strips or finishing
been shown to improve the accuracy of IPR. (b) Ortho- Ortho-strips. (d) Diamond-coated discs can be difficult to
strips mounted on a contra-angle low-speed handpiece operate and risk soft tissue injury to the patient’s lips and
allow for precise IPR in both anterior and posterior seg- cheeks. Discs are also prone to creating ledges from
ments. The strips range from 0.1 mm-0.5 mm in thick- improperly angled cuts into the enamel. (e) The bitewing
ness. (c) For 0.5 mm IPR in both anterior and posterior radiograph shows ledges were created by inadequately
segments, a 0.5 mm diamond bur can remove the desired angled cuts with diamond discs during IPR, increasing the
amount of enamel, even in severely crowded segments. patient’s risk for periodontal disease and caries
References 99
single visit for patient comfort, rather than dis- with distalization and extraction therapy in clear
tributed sporadically over the course of treat- aligners. Nevertheless, clinicians should incorpo-
ment. This can be achieved with a method that rate IPR with the same pragmatic mindset toward
allows for access into obstructed areas. The IPR its use in treatment planning, regardless of the
visit should be afforded ample time and be exclu- appliance. That is, IPR should be planned judi-
sively performed by the clinician, rather than by ciously and safely, within the limits of healthy
any dental auxiliaries such as hygienists or orth- amounts of enamel removal and biological tooth
odontic assistants. movement, and should not be an indication for
unnecessary tooth movement and round
tripping.
Long Term Consequences of IPR
Some clinicians have expressed concerns over References

potential damage to the periodontium as a
sequelae of IPR. Specifically, Vanarsdall Jr., 1. Rao V, George AM, Sahu SK, Krishnaswamy
NR. Surface roughness evaluation of enamel after
based on monkey studies, recommended IPR various stripping methods by using profilometer. Arch
should be avoided in patients with normal attach- Oral Sci Res. 2011;1:190–7.
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Vanarsdall Jr. claimed that IPR could lead to loss reduction as a part of orthodontic treatment.
Stomatologija. 2014;16(1):19–24.
of attachment, intercrestal bone loss, and poor 3. Kalemaj Z, Levrini L. Quantitative evaluation of
root proximity. However, a number of studies implemented interproximal enamel reduction during
have contradicted these claims. Notably, research- aligner therapy: a prospective observational study.
ers observed no deterioration in the periodontium Angle Orthod. 2021;91(1):61–6.
4. Pindoria J, Fleming PS, Sharma PK. Inter-proximal
10 years following IPR [21]. Recent studies have enamel. Br Dent J. 2016;221(12):757–63.
also shown a slight increase in interradicular 5. De Felice ME, Nucci L, Fiori A, Flores-Mir C, Perillo
bone volume following clear aligner therapy and L, Grassia V. Accuracy of interproximal enamel
IPR in patients at high risk for periodontal dis- reduction during clear aligner treatment. Prog Orthod.
2020;21(1):28.
ease (though this increase occurred indepen- 6. Kravitz ND, Kusnoto B, BeGole E, Obrez A, Agran
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relationship between increased caries risk and ment with Invisalign. Am J Orthod Dentofac Orthop.
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concluded that the incidence of caries on abraded Angle Orthod. 2015;15:881–9.
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surfaces treated with IPR was statistically the Schneider PP, Kim KB. Class II malocclusion cor-
same as that on intact surfaces [24]. rection with Invisalign: is it possible? Am J Orthod
Dentofac Orthop. 2021;159(1):e41–8.
eflections on IPR in Clear Aligner
R 10. Othman SA, Harradine NW. Tooth-size discrepancy
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formed is significantly greater in clear aligner tive follow-up study on the efficacy of tooth move-
therapy than fixed appliances (though it is fre- 2020;158(3):420–5.
quently employed in fixed appliances), primarily 12. Janson G, de Freitas MR, Araki J, Franco EJ, Barros
as a means to compensate for less predictability SE. Class III subdivision malocclusion corrected with
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Dilemmas in Bite Opening
6
Contents
The Challenge of Deep Bite Correction 101
Factors in Bite Opening 102
Treatment Protocols 106
Improving the Accuracy of Bite Opening 112
References 112
he Challenge of Deep Bite

T areas for leveling the Curve of Spee through
Correction improved predictability of premolar extrusion
and anterior intrusion [3]. Also, the protocol
One of the most difficult challenges of clear allowed for the addition of bite ramps on the lin-
aligner therapy remains deep bite correction. A gual surfaces of maxillary incisors and canines to
2017 study showed that only 1.5 mm of improve- supplement mandibular incisor intrusion and to
ment in overbite could be predictably achieved disocclude the posterior teeth during bite opening
with clear aligner therapy, which is significantly [3]. In late 2020, Invisalign incorporated G8 fea-
less than that typically corrected with fixed appli- tures, which sought to improve the efficacy of
ances [1]. Clear aligner therapy’s limited capabil- bite opening. Specifically, one of the features tar-
ity in bite opening is likely associated with its gets anterior intrusion with specific contours in
low accuracy of incisor intrusion and molar the aligners for greater control of force systems
extrusion compared to higher accuracy for move- and the reduction of unwanted movements [4].
ments involved in bite closure, such as incisor Despite the limitations of the appliance, suc-
extrusion and molar intrusion [2]. The control of cessful management of the vertical dimension,
the vertical dimension can be particularly chal- both during bite closure and bite opening, can
lenging during extraction therapy, which tends to be achieved with clear aligner therapy through
cause bite deepening. Since its creation, judicious treatment planning, strategic mecha-
Invisalign has incorporated a number of modifi- notherapy during the treatment setup and
cations to address deep bite correction. In 2013, throughout the course of therapy, and the ade-
Invisalign introduced its G5 protocol, which quate incorporation of adjuncts such as TADs
included optimized attachments and pressure and intermaxillary elastics. Studies have shown
https://doi.org/10.1007/978-3-030-92810-0_6
102 6 Dilemmas in Bite Opening
successful outcomes with selective incorpora- clinician should confirm that the maxillary and
tion of the G5 protocol and treatment methods mandibular Curves of Spee have been adequately
for bite opening such as overengineering the leveled.
leveling of the Curve of Spee [5]. In this chap-
ter, we discuss the current challenges in control-
ling the vertical dimension, approaches in Bite Ramps
treatment planning, and mechanotherapy for the
management of mild to severe deep bites. Bite ramps were introduced in 2013 as part of
Invisalign’s G5 protocol and later became avail-
able as an option for Invisalign retainers in
Factors in Bite Opening patients with deep bites (Fig. 6.1). They often
have to be prescribed by the clinician during the
Leveling the Curve of Spee initial setup for placement on the maxillary cen-
tral and lateral incisors or all anterior teeth,
Like in fixed appliances, the failure of bite open- including the maxillary canines. The G8 modifi-
ing is often associated with inadequate leveling cations incorporated an additional option of the
of the Curve of Spee in either the maxillary, man- automatic placement of bite ramps when intru-
dibular arch, or both arches. This is attributed to sion of the mandibular incisors greater than
either insufficient intrusion of the anterior teeth, 1.5 mm has been programmed (Fig. 6.2).
insufficient extrusion in the buccal segments, or a However, one of the weaknesses of bite ramp
combination. Cephalometric analyses have prescription is the current limitation on the clini-
shown that deep bite correction in clear aligners cian’s ability to manipulate both its position and
occurs primarily through the proclination of the size. At present, in the Invisalign software, once
mandibular incisors, along with the intrusion of the clinician requests bite ramps, they are auto-
maxillary incisors and the extrusion of mandibu- matically placed by the software and cannot be
lar molars [1]. Therefore, it is important that subsequently adjusted. This is problematic
when indicated, these intrusive and extrusive because the software frequently places the bite
movements are planned for bite opening. In the ramps in sites that do not adequately contact the
treatment planning of most deep bite cases, the opposing teeth and therefore do not assist in bite
a b
Fig. 6.1 (a) The G5 protocol includes the option of bite all maxillary anterior teeth. It also incorporated optimized
ramp placement on either the lingual surfaces of the max- extrusion attachments for the premolars, as shown on the
illary central and lateral incisors or the lingual surfaces of maxillary right second premolar in (b)
Invisalign G8 offers:
Improvements to
predictability in deep bite
correction
Improvements to
predictability in
moderate/severe crowding
and cross bite cases
Reduction in the
likelihood of posterior
open bite (POB)
Fig. 6.2 In late 2020, Invisalign introduced the G8 modi-

fications to improve the efficacy of bite opening. When
intrusion of the mandibular anterior teeth was pro- Fig. 6.3 The Invisalign software’s default placement of
grammed to be greater than 1.5 mm, specific aligner con- bite ramps may be nonideal, resulting in lack of occlusion
touring would be automatically incorporated to optimize with the opposing incisors and poor functionality. Ideally,
intrusion. The efficacy of these G8 modifications has not the clinician should be given free manipulation of bite
been rigorously evaluated in clinical trials ramps for proper contact with the opposing incisors and
adequate disocclusion of the posterior segments
opening (Fig. 6.3). In other cases, the software
delays the placement of the bite ramps due to
anatomical limitations. Ideally, the position, size, segments (Fig. 6.4). Alternatively, certain clear
and timing of the bite ramps should be freely aligner software such as U-Lab allows the clini-
determined by the clinician to optimize the func- cian the freedom to manipulate bite ramps so that
tionality of the bite ramps as early as possible they can be placed on any lingual surface and
during treatment. Recent studies have shown sig- sized for optimal function during the develop-
nificant improvement in overbite in deep bite ment of the treatment plan.
patients with the use of bite ramps and the G5
protocol (though this improvement in overbite
was less than that achieved in a group treated G8 Modifications
with fixed appliances) [5].
Though Invisalign does not permit the free In late 2020, Invisalign introduced the G8 modi-
manipulation of bite ramps, the clinician can fications, which focused on the prevention of
directly incorporate bite ramps in more ideal posterior open bites and increasing the efficacy of
positions on the aligner with the use of hand bite opening. In addition to the automatic place-
instruments. For example, in severely deep bite ment of bite ramps, the aligner in the mandibular
cases, the bite ramps on the lingual surfaces of anterior teeth would be contoured for the
the maxillary incisors and canines may not con- enhancement of intrusion and the control of
tact the opposing teeth and be nonfunctional. In unwanted movements when mandibular anterior
these cases, the clinician can manually add bite intrusion exceeded 1.5 mm. However, at present,
ramps on the lingual surfaces of the maxillary no high-quality studies have been performed on
incisors and canines for contact with the oppos- the G8 protocol and its effects on bite opening are
ing arch to adequately disocclude the posterior still unknown.
Fig. 6.4 In severely deep bite cases, the clinician can sion. A bite ramp plier can be employed for the placement
manually incorporate bite ramps on the lingual surfaces of of a bite ramp in a more ideal location at any time during
the maxillary teeth for more functional posterior disocclu- a course of aligners
Relative Intrusion crowded anterior teeth, the incisors can be over-

retracted, resulting in an undesired deepening
Studies have demonstrated that the relative intru- of the bite. The recovery of deep bites with
sion of the mandibular incisors through proclina- over-retracted incisors to normal inclinations
tion constitutes one of the principal mechanics can be challenging, requiring significant ante-
for bite opening [1]. In deep bite cases, it is rior intrusion and lingual root torque, which
important to incorporate adequate lingual root have been shown to be problematic movements
torque to upright maxillary or mandibular inci- with clear aligners. The normalization of over-
sors for relative intrusion and more predictable retracted incisors and their associated deep
bite opening. The addition of power ridges or overbites may require auxiliaries, such as TAD-
other analogous alterations in aligner geometry supported intrusion.
in other types of clear aligners have been shown
to enhance incisor torque [6]. Therefore, they
should be incorporated for lingual root torque Short Clinical Crowns
and relative intrusion, when indicated (Fig. 6.5).
In cases where lingual root torque in the man- Short clinical anterior crowns can be a limiting
dibular incisors is required, Class II elastics can factor in bite opening, even when G5 protocols
be a useful auxiliary. are applied. In these cases, the limited surface
In the decrowding of an arch, especially area of the crowns adversely affects the predict-
anterior segments, the placement of the lingual ability of intrusive movements (Fig. 6.6). The cli-
root torque should be balanced with the appro- nician may consider overcorrection of intrusive
priate amount of IPR. For example, if the movements to achieve bite opening in these
planned IPR is excessive for a segment of patients.
Fig. 6.5 For patient J. L., the placement of power ridges method should especially be considered for the treatment
on the mandibular incisors supplements both lingual root of deep bite cases with upright mandibular incisors
torque and bite opening through relative intrusion. This
Fig. 6.6 Short clinical crowns with limited surface area for encapsulation by the aligner will adversely affect the pre-
dictability of intrusive movements and likely require overengineering to achieve ideal overbite
Treatment Protocols In the design of the Clincheck, the intrusion of

the maxillary anterior teeth should be overengi-
TAD-Supported Intrusion neered to a 0 mm overbite or an edge-to-edge
position to enhance the bite opening. However,
Clear aligner therapy has been shown to achieve the need for pure intrusion of greater than
1–2 mm of pure intrusion, though with limited 3–4 mm is an indication for surgical correction,
accuracy [7]. In cases requiring more significant such as a Lefort I osteotomy.
intrusion of the maxillary incisors, such as
3–4 mm, the clinician can supplement intrusive
movements with temporary skeletal devices in Extraction Cases
the labial bone between the maxillary central and
lateral incisors or between the maxillary lateral Extraction cases are associated with bite deepen-
incisors and canines. Elastics can then be applied ing due to the tendency of the maxillary or man-
bilaterally from the skeletal attachments to preci- dibular incisors to lose torque and extrude during
sion cuts within the anterior region of the aligner. space closure. Studies of clear aligner therapy
This form of TAD-supported intrusion can be with first premolar extractions have shown
effective for the reduction of gingival display in greater lingual crown torque and extrusion in the
patients with vertical maxillary excess (Fig. 6.7). maxillary central incisors than predicted [8]. The
Fig. 6.7 (a−e) TAD-supported intrusion can be effective cuts on the upper aligner to the two TADs. (f−h) For
for the reduction of gingival display in patients with verti- patient Q. W., progress records show TAD-supported
cal maxillary excess when intrusion of 3–4 mm of the intrusion with clear aligners allowed for significant maxil-
maxillary incisors are required. The treatment achieved lary incisor intrusion and reduction of gingival display.
both ideal overbite and the correction of the Class II rela- The patient was instructed to wear full-time vertical elas-
tionships on both sides. The maxillary and mandibular tics (1/4’’, 4 oz. and 1/4’’, 6 oz.) from precision cuts on the
incisors were retracted into normal range. Throughout aligner to the TADs
treatment, the patient wore vertical elastics from precision
f g

Fig. 6.8 In this case, both maxillary first premolars were premolars rather than four premolars reduced the diffi-
extracted, while IPR and slight expansion were performed culty of establishing an ideal overbite, which was achieved
to decrowd the mandibular arch and control the mandibu- after an initial and a single refinement course
lar incisor inclinations. The extraction of two maxillary
clinician should especially anticipate bite deep- Extraction of maxillary premolars as opposed to
ening as a result of loss of torque in the maxillary the four first premolars may lessen the difficulty
incisors in cases with maxillary extractions and of achieving an ideal overbite. A two premolar
in the mandibular incisors when mandibular teeth extraction pattern may be more suitable than a
have been extracted. Therefore, the clinician will four premolar extraction pattern for hypodiver-
often have to incorporate the G5 protocol in gent patients, in which bite opening is especially
extraction cases to minimize bite deepening. challenging.
Also, if intrusive movements are applied to the
maxillary or mandibular incisors, the clinician
should consider overcorrection to achieve an Molar Extrusion
ideal overbite at the end of treatment.
The limitations of clear aligners in control- In patients with extremely deep bites and under-
ling incisor torque may require more conserva- lying normodivergent or hypodivergent skeletal
tive approaches toward extraction therapy. In patterns, anterior intrusion can be supplemented
Class II malocclusions with increased overjet with molar extrusion for bite opening. This
and maxillary and mandibular crowding, an approach is similar to the mechanotherapy pro-
extraction pattern of four first premolars may duced in fixed appliances by a 2 × 4 setup with
lead to difficulty in bite opening due to loss of tip-back bends mesial to both first molars
torque in the mandibular incisors during space (Fig. 6.9). Following the use of this protocol, the
closure. A viable alternative treatment to this buccal segments of premolars may require addi-
type of malocclusion is the extraction of only the tional extrusion in a course of refinement for
maxillary first premolars and judicious IPR and ideal interdigitation and complete leveling of the
expansion of the mandibular arch (Fig. 6.8). Curve of Spee.
Fig. 6.9 For severe deep bites and normodivergent or through leveling of the maxillary and mandibular curves
hypodivergent skeletal patterns, the clinician should con- of Spee through intrusion of the maxillary and mandibular
sider molar extrusion for bite opening. Patient C. W. pre- incisors. Class II canine and molar relationships were cor-
sented with a 100% overbite, hypodivergent vertical rected with distalization of the maxillary arch and poste-
pattern, and Class II div II malocclusion. The maxillary rior IPR. The final occlusion showed Class I canines and
right first and second molars were extruded to supplement molars, bilaterally, ideal overjet, and ideal overbite
bite opening. Complete bite opening was also achieved


I mproving the Accuracy of Bite 2. Haouili N, Kravitz ND, Vaid NR, Ferguson DJ,
Opening tive follow-up study on the efficacy of tooth move-
It remains unclear how the G8 modifications will 2020;158(3):420–5.
affect the predictability of maxillary and man- 3. Align Technology. Align Technology announces
Invisalign G5 innovations for treatment of deep
dibular incisor intrusion and the overall efficacy bite. 2013. https://investor.aligntech.com/index.php/
of bite opening. Nevertheless, the accuracy of news-releases/news-release-details/align-technology-
bite opening in clear aligner therapy can be announces-i nvisalign-g 5-i nnovations-t reatment.
improved through the incorporation of the appro- Accessed 16 Mar 2021.
4. Align Technology. Align Technology announces
priate protocols—the G5 protocol or its equiva- Invisalign G8 with new Smartforce aligner activa-
lent in other clear aligner software, the tion features. 2020. https://investor.aligntech.com/
incorporation of relative intrusion when indi- news-releases/news-release-details/align-technology-
cated, overengineering intrusive movements, announces-invisalign-g8-new-smartforce. Accessed
18 Mar 2021.
judicious planning of IPR, and conservative 5. Henick D, Dayan W, Dunford R, Warunek S, Al-Jewair
approaches to extraction therapy. Adjuncts such T. Effects of Invisalign (G5) with virtual bite ramps
as TADs and intermaxillary elastics can supple- for skeletal deep overbite malocclusion correction in
ment movements, such as pure intrusion or rela- adults. Angle Orthod. 2021;91(2):164–70.
tive intrusion through labialization of the C. Treatment outcome and efficacy of an aligner
mandibular incisors. Ultimately, these treatment technique--regarding incisor torque, premolar dero-
methods work toward adequate leveling of the tation and molar distalization. BMC Oral Health.
maxillary and mandibular Curves of Spee, which 2014;14:68.
7. Al-Balaa M, Li H, Ma Mohamed A, Xia L, Liu W,
is the central tenet to successful bite opening. Chen Y, Omran T, Li S, Hua X. Predicted and actual
outcome of anterior intrusion with Invisalign assessed
with cone-beam computed tomography. Am J Orthod
References Dentofac Orthop. 2021;159(3):e275–80.
1. Khosravi R, Cohanim B, Hujoel P, Daher S, Neal M,
Liu W, Huang G. Management of overbite with the
Invisalign appliance. Am J Orthod Dentofac Orthop.
2019;89(5):679–87.
2017;151(4):691–699.e2.
Dilemmas in Open Bite Correction
7
Contents
Current Strategies for Open Bite Closure 113
Efficacy of Movements Associated with Bite Closure 114
Factors Affecting Bite Closure 118
The Reality of Molar Intrusion during Open Bite Closure 118
The Incorporation of Bite Jumps 120
TAD-Assisted Molar Intrusion for Bite Closure 120
The Reality of Open Bite Closure with Clear Aligner Therapy 122
References 124
urrent Strategies for Open Bite

C phatic tissues, either the tonsils or adenoids, can
Closure lead to airway obstruction, followed by long-
term mouth breathing, and resulting in maxillary
Anterior open bites constitute one of the most constriction and a vertical growth pattern [2].
challenging malocclusions for orthodontic man- Untreated open bites are associated with func-
agement. The difficulty lies in the multifactorial tional and psychological issues in patients,
etiology, the complexity of the treatment including difficulties incising food, speech
mechanics, and the high rate of relapse. Open issues, and facial appearance [3].
bites can be composed of dental, skeletal, respi- A variety of modalities has been employed for
ratory, neurological, or functional components bite closure, including habit appliances such as
[1]. They are often categorized as dental, skele- the tongue crib, functional appliances with ortho-
tal, or a combination of both. Skeletal dysplasias pedic forces such as the high-pull headgear,
characterized by excessively vertical patterns of occlusal equilibration, orthodontic camouflage
growth can result in anterior open bites. They are with or without extraction, the use of skeletal
also associated with oral habits, such as digit anchorage devices in the forms of mini-implants
sucking, and the soft tissues, such as lip incom- and miniplates, and surgical forms of correction
petence, abnormal swallowing patterns, and [4]. A meta-analysis on the long-term stability of
abnormal tongue positioning. Hypertrophic lym- open bite correction found 75% stability in open
https://doi.org/10.1007/978-3-030-92810-0_7
114 7 Dilemmas in Open Bite Correction
bites treated nonsurgically, while a stability of fficacy of Movements Associated

E
82% for surgical treatments [5]. In nonsurgical with Bite Closure
treatment, the mechanics usually involves extru-
sion of the anterior segments, intrusion of poste- bsolute Extrusion vs. Relative
A
rior segments to facilitate autorotation of the Extrusion
mandible, or a combination of both. In certain
cases, clinicians have shown successful closure Studies have observed the accuracy of pure extru-
of severe skeletal open bites with the intrusion of sion of the maxillary central and lateral incisors
maxillary and mandibular molars with mini- to be 55% [12]. This represents a marked
implants as a viable alternative to major orthog- improvement over that of previous generations of
nathic surgery [6]. aligners, which demonstrated an accuracy for
Clinicians have successfully achieved open extrusion of 18.3% for maxillary incisors and
bite correction with clear aligners, especially for 24.5% for mandibular incisors. However, it
the treatment of mild anterior open bites [7]. remains difficult to achieve pure anterior extru-
Clear aligners have been claimed to allow for sion of greater than 1 mm in either the maxillary
both vertical control and a bite block effect, fac- or mandibular arch and greater than 2 mm col-
tors helpful for bite closure [8]. Invisalign’s G4 lectively in both arches (Fig. 7.1). Studies show
modifications targeted extrusion of the anterior that during open bite closure, the average abso-
segments through optimized attachments on the lute extrusion of the maxillary and mandibular
maxillary incisors [9]. Clear aligners have also incisors remains less than 1 mm per arch [8].
demonstrated efficacy with movements associ- One of the essential strategies for open bite
ated with bite closure, including posterior intru- closure is the prescription of relative extrusion of
sion and the extrusion of anterior segments. the maxillary and mandibular incisors, or extru-
Recent clinical trials have shown that open bite sion of the incisors achieved through the combi-
closure with clear aligners occurs through a com- nation of extrusion with lingual crown tipping
bination of posterior intrusion, extrusion of the during incisor retraction. Relative extrusion,
anterior segments, and slight mandibular autoro- when compared to absolute or true extrusion,
tation [10]. A number of clinicians have also allows for greater and more predictable extrusion
supplemented clear aligner treatment with mini- of the maxillary and mandibular incisors
implants for greater control over posterior intru- (Fig. 7.2) [13]. However, relative extrusion can
sion movements [11]. only be achieved when spacing is present in the
As with fixed appliances, the success of open respective arch, either through IPR, extractions,
bite treatment with clear aligners depends fore- or existing spaces. When relative extrusion is pre-
most on the accurate diagnosis and management scribed through retraction, whether through IPR
of the etiologic factors causing the open bite. or extractions, the amount of extrusion achieved
With respect to clear aligner mechanotherapy, the can be up to 2 mm per arch and up to 4 mm in
predictability of bite closure can be improved combination from both arches.
with strategic planning of posterior intrusive and Invisalign’s G4 modifications targeted open
anterior extrusive movements and the selective bite closure by incorporating optimized extrusion
incorporation of mini-implants for enhanced con- attachments for the maxillary and mandibular
trol over posterior intrusion. In this chapter, we incisors (Fig. 7.3). Clinical trials have suggested
describe the principles for treatment planning that the addition of optimized extrusion attach-
and optimizing the mechanotherapy involved in ments enhanced the accuracy of incisor extrusion
bite closure. compared with the accuracy in aligners prior to
Fig. 7.1 In the treatment of mild anterior open bites, tem, these extrusive movements can be supplemented
absolute extrusion can be programmed for the maxillary with G4 optimized attachments
and mandibular incisors. Typically, in the Invisalign sys-
the G4 modifications [12]. Therefore, it is recom- tion, which allows for the reduction in the verti-
mended that G4 attachments be placed on inci- cal dimension, the closure of the mandibular
sors when absolute extrusion is planned, while plane, decreases in the lower anterior facial
their placement is optional for relative extrusion. height, and increased stability [10]. Therefore, it
This is because, during relative extrusion, the is recommended that when indicated, such as in
predictability of the extrusive movement has high-angle patients or over-erupted posterior
already been enhanced by lingual crown tipping. teeth, the clinician couple anterior extrusive
movements with programmed intrusion of the
maxillary and mandibular molars for more pre-
Molar Intrusion dictable bite closure (Fig. 7.4).
There have been claims of a “bite block effect”
Studies have demonstrated that clear aligner ther- associated with clear aligners due to the thick-
apy is able to induce significant intrusion of both ness of the aligner along with the forces exerted
the maxillary and mandibular molars, even with- by the patient during mastication [15]. Studies
out the supplementation of TADs. One of the have shown that intrusion of the molars of up to
most effective methods of open bite closure is the 0.5 mm can occur even when intrusive move-
combination of molar intrusion and both absolute ments have not been programmed by the clini-
and relative extrusion of the maxillary and man- cian [16]. However, it is questionable that clear
dibular incisors. 1 mm of molar intrusion has aligners can simulate the bite block effects pro-
been shown to result in approximately 2–3 mm of duced by conventional functional appliances with
anterior open bite closure [14]. Molar intrusion posterior bite blocks of greater than 3 mm thick-
has been shown to result in mandibular autorota- ness, which allow for much greater and long-term
Fig. 7.2 For the treatment of this Class I malocclusion lary and mandibular incisors allowed for their relative
with moderate maxillary and mandibular crowding, mod- extrusion, which was essential for this patient’s anterior
erate anterior open bite, and bimaxillary protrusion, we open bite closure
extracted four first premolars. The retraction of the maxil-

Fig. 7.3 One of the G4 modifications included optimized consider omitting these attachments when other predict-
extrusion attachments to enhance the extrusion of the able means of extrusion have been planned, such as rela-
maxillary incisors. These attachments are triggered when tive extrusion through maxillary incisor retraction
programmed extrusion exceeds 0.5 mm. The clinician can
intrusive forces on the posterior teeth. ioral shaping to cease oral habits or abnormal
Nevertheless, the nature of the clear aligner, with functions, habit appliances such as tongue cribs
its full coverage of the dentition, represents an or spurs, or a combination of these modalities
advantage during intrusion because it limits [17]. When indicated, more invasive intervention
undesired extrusive movements. may be required, such as in the case of mouth
breathing, which may warrant a referral to the
otolaryngologist for evaluation of the lymphatic
inishing after Anterior Open Bite
F tissues and their removal. The addressing of these
Closure factors allows for improved predictability of
mechanotherapy during open bite treatment.
Following the closure of the anterior open bite, a
lateral open bite frequently develops due to heavy
anterior interferences (Fig. 7.5). In these cases, he Reality of Molar Intrusion
T
the buccal segments need to be extruded either during Open Bite Closure
through an additional course of aligners, vertical
elastics, or a combination of the two methods. Although maxillary and mandibular molar intru-
The clinician should also consider alleviation of sion are routinely programmed for open bite clo-
the heavy anterior contacts to facilitate closure of sure, the majority of closure occurs through
the lateral open bite. anterior extrusion, whether absolute or relative,
as opposed to molar intrusion and mandibular
autorotation. An early study of open bite treat-
Factors Affecting Bite Closure ment without the use of auxiliaries such as TADs
concluded that the primary mechanism for bite
As in fixed appliances, the success of open bite closure occurred through extrusion of the ante-
treatment largely depends on the removal of rior teeth [18]. This is also supported by recent
functional etiological factors prior to any mecha- studies which have observed there were more
notherapy. These range from tongue disposition, dental than skeletal changes contributing to open
digital habits, abnormal swallowing pattern, to bite closure with clear aligner therapy [10].
mouth breathing. These can be addressed either It is difficult to achieve molar intrusion greater
through myofunctional therapy, forms of behav- than 1 mm in a single arch without skeletal
The Reality of Molar Intrusion during Open Bite Closure 119
Fig. 7.4 (a) For adult patient H.S., who presented with a anterior open bite. We planned for significant relative
severe anterior open bite, increased overjet, and Class II extrusion of the maxillary incisors through retraction, as
div I malocclusion, treatment included the extraction of shown in the tooth movement assessment table. Light
maxillary first premolars and intrusion of the maxillary Class II elastics (1/4”, 2.7 oz) were worn to supplement
molars. A bite jump was programmed on stage 28 (b, c) retraction of the maxillary incisors
for mandibular autorotation and complete closure of the
Fig. 7.5 Autorotation of the mandible for anterior open illary aligner to allow for occlusal settling, while more
bite closure will often result in lateral open bites. Mild severe lateral open bites may require vertical elastics or a
lateral open bites can be corrected by sectioning the max- refinement course for complete closure
2 mm per tooth, and therefore greater than 4 mm

collectively for both arches.
The Incorporation of Bite Jumps
In the Clincheck plan of open bite closure, the

bite jump simulates the closure of the anterior
open bite (Fig. 7.7). It is important to program the
bite jump into the Clincheck to accurately model
the course of treatment. However, though the bite
jump will simulate an autorotation of the mandi-
ble, it is unlikely significant autorotation is
Fig. 7.6 A TAD can be placed on both the buccal and achieved in nonsurgical treatment without skele-
palatal sides of the molar to be intruded. The patient can
tal anchorage and more likely that the bite clo-
wear an elastic (with a tension of ¼″, 4 oz. or 6 oz.) from
the buccal to the palatal TAD to supplement intrusion to sure occurred through dental movements.
the molar The bite jump is typically prescribed within
the final aligner, though bite closure will often
occur earlier. It is difficult to predict when ante-
anchorage. Studies typically show both maxillary rior open bite closure or the bite jump will actu-
and mandibular molar intrusion of <1 mm during ally occur during treatment, but it is usually
bite closure and <2 mm of intrusion additively observed in the middle of a course of aligners or
from both arches. If >1 mm of intrusion is occasionally, as early as the first third of treat-
desired, then it is necessary to supplement intru- ment (Fig. 7.8).
sion with TADs. The miniscrews can be placed in
the buccal and palatal bone respective to the tooth
requiring intrusion. A power chain can be AD-Assisted Molar Intrusion
T
extended between the two TADs for the exertion for Bite Closure
of an intrusive force as bodily as possible
(Fig. 7.6). Intrusion of <1 mm per maxillary and Ideally, when indicated, skeletal anchorage
mandibular molars has been shown to result in should be incorporated for bite closure so that
the autorotation of the mandible and closure of miniscrews can supplement both maxillary and
the mandibular plane [8]. However, it is still dif- mandibular molar intrusion. However, clinicians
ficult to achieve molar intrusion of greater than have shown success with either exclusively
TAD-Assisted Molar Intrusion for Bite Closure 121
Fig. 7.7 Stage 23 represents a bite jump, portraying man- premolars and molars, while significant relative extrusion
dibular autorotation for anterior open bite closure. was programmed for the maxillary and mandibular
Significant intrusion was programmed for the maxillary incisors
intruding the maxillary molars or exclusively intrusion of the mandibular molars with skeletal
intruding the mandibular molars in fixed appli- anchorage [20]. Therefore, the clinician may
ances [19]. Recent reports have shown similar consider a therapeutic diagnosis by incorporating
success with clear aligners by supplementing skeletal anchorage for the intrusion of molars in
one arch and then reevaluating during treatment he Reality of Open Bite Closure
T
the need for skeletal anchorage for molar intru- with Clear Aligner Therapy
sion in the opposing arch. This approach is less
invasive than placing skeletal anchors in both Whether in fixed appliances or clear aligner ther-
arches at the outset, especially as the literature apy, the successful treatment of open bites
has demonstrated efficacy with bite closure using requires the accurate diagnosis of its etiology and
skeletal anchorage in a single arch. the removal or management of any functional
The incorporation of skeletal anchorage for contributory factors, such as mouth breathing and
open bite treatment has been shown to decrease tongue disposition. The principal therapeutic
treatment time compared to treatments without modalities of bite closure to target the dental and
skeletal anchorage, either with or without extrac- skeletal components of the malocclusion are
tions. In fixed appliances, open bite treatments extrusion of the anterior segments and intrusion
supported by skeletal anchorage have also been of the posterior segments, both of which are often
observed to achieve stability similar to that of combined during therapy. In clear aligner ther-
surgical approaches, though relapse ranging from apy, the predictability of anterior extrusion can be
10 to 30% has been observed for maxillary and enhanced by combining true extrusion with more
mandibular molars that have been intruded with predictable movements, such as lingual crown
skeletal anchorage [21]. tip, while the predictability of significant poste-
Fig. 7.8 For patient T. S., the anterior open bite was The bite jump or anterior open bite closure occurred after
treated with both extrusion of the maxillary and mandibu- 5 months of treatment, or within the first third of the total
lar incisors and maxillary and mandibular molar intrusion. treatment duration
The Reality of Open Bite Closure with Clear Aligner Therapy 123

rior intrusion can be enhanced with the judicious 10. Harris K, Ojima K, Dan C, Upadhyay M, Alshehri A,
Kuo CL, Mu J, Uribe F, Nanda R. Evaluation of open
use of skeletal anchorage. bite closure using clear aligners: a retrospective study.
It has been shown that anterior open bites with Prog Orthod. 2020;21(1):23.
nonsurgical clear aligner therapy are closed 11. Giancotti A, Germano F, Muzzi F, Greco M. A
through a combination of incisor extrusion, molar miniscrew-supported intrusion auxiliary for open-
bite treatment with Invisalign. J Clin Orthod.
intrusion, and mandibular autorotation. However, 2014;48(6):348–58.
the evidence also demonstrates bite closure 12. Haouili N, Kravitz ND, Vaid NR, Ferguson DJ,
occurs more through dental than skeletal changes Makki L. Has Invisalign improved? A prospec-
and that only slight mandibular autorotation tive follow-up study on the efficacy of tooth move-
occurs during treatment. 2020;158(3):420–5.
13. Kravitz ND, Kusnoto B, BeGole E, Obrez A, Agran
B. How well does Invisalign work? A prospective
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and central incisors: first premolar extraction treatment
and treatment. Oral Health. 1990;80(1):27–31.
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4. Matsumoto MA, Romano FL, Ferreira JT, Valério
17. Tanny L, Huang B, Naung NY, Currie G. Non-
RA. Open bite: diagnosis, treatment and stability.
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T, Hujoel P. Stability of treatment for anterior open-
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Power Ridges: How Powerful
Are They?
8
Contents
Torquing with Clear Aligners 125
The Indications of Power Ridges 126
The Efficacy of Power Ridges 132
Controlling Torque with Clear Aligners 134
References 134
Torquing with Clear Aligners that clear aligners are more than twice as predict-
able at performing pure crown tipping than torque
Torque expression is one of the most important in incisors [3]. It has also been shown that labial
elements of orthodontic treatment. The faciolin- root movement is significantly more accurate
gual inclination of the crown is considered the than lingual root movement with clear aligners
third key of occlusion. Torque control in both the [3]. This result has been partly explained by the
anterior and posterior segments is critical for greater prevalence of root fenestrations in the
achieving ideal overjet and overbite, adequate labial side compared to that in the lingual side
anterior guidance, balanced occlusal contacts, [4]. In clear aligners, the inadequate expression
and optimal distribution of spaces [1]. Torque is of torque commonly results in excessive crown
also critical for smile esthetics and a harmonious tipping during translation. For example, during
soft tissue profile. Inadequate torque can result in the retraction of the maxillary incisors, loss of
poor lip support, reduced buccal corridors, and incisor torque can occur due to excessive lingual
occlusal interferences. crown tip and inadequate expression of lingual
The efficacy of torque expression in clear root torque.
aligner therapy has been studied in clinical trials The primary adjunct for torquing movements
and in vitro biomechanical simulations. Studies in clear aligners is the alteration of aligner geom-
have shown that buccal-lingual crown tip is one etry in the form of a pressure line located at the
of the most accurate movements with clear align- cervical region on the facial surface of the crown.
ers, when compared to movements in the other In the Invisalign system, this feature is known as
dimensions, such as rotation and intrusion [2]. the power ridge. It has been shown that the incor-
However, recent studies have also demonstrated poration of a power ridge allows for the generation
https://doi.org/10.1007/978-3-030-92810-0_8
126 8 Power Ridges: How Powerful Are They?
of a greater moment for the desired torquing division 1 cases requiring maxillary incisor
movement [5]. The true effect of power ridges on retraction and Class I bimaxillary protrusion
torquing efficacy has not been determined, cases requiring both maxillary and mandibular
though they have been demonstrated to improve incisor retraction (Fig. 8.3). A study on the effi-
the accuracy of incisor torquing [6]. cacy of extraction therapy with clear aligners
The use of power ridges is not limited to con- observed greater lingual crown torque and extru-
trolling maxillary incisor torque during incisor sion than predicted [7]. The clinicians neglected
retraction, but also extends to a wide range of to place power ridges or attachments to supple-
applications, including maintaining incisor incli- ment lingual root torque. They recommended the
nation during posterior protraction, dental use of power ridges, attachments, or overcorrec-
decompensation for orthognathic surgery, treat- tion with greater facial crown inclination for
ment of Class II and Class III malocclusions, and torque control in extraction therapy [7]. In
the detailing of lingually displaced teeth. In this extraction cases with significant retraction of the
chapter, we discuss the efficacy of power ridges, maxillary or mandibular incisors, power ridges
the indications and mechanotherapy for their use, can often be combined with intrusion to control
and modifications in design to address their cur- both the inclination and vertical position of the
rent limitations. incisors. Frequently, the amount of anterior
intrusion has to be exaggerated to compensate
for bite deepening during retraction, so the
The Indications of Power Ridges Clincheck simulation may show an edge-to-edge
overbite at the end of treatment (Fig. 8.4).
Incisor Retraction
The most common indication for the use of Posterior Protraction

power ridges is to control incisor torque during
retraction (Fig. 8.1). The incorporation of power The incorporation of power ridges is also impor-
ridges is important to prevent over-retraction of tant for controlling incisor torque when protract-
either the maxillary or mandibular incisors ing posterior teeth during space closure. In the
(Fig. 8.2). Supplementation with power ridges arch where posterior protraction is desired, the
should be considered for incisors planned for power ridges will function as anterior anchorage
significant retraction in extraction therapy and to supplement either the maintaining or labializa-
non-extraction therapy, especially in Class II tion of the incisors (Fig. 8.5). This use of power
ridges is indicated in cases with significant exist-
ing spaces, posterior protraction in the maxillary
arch in Class III treatment, or posterior protrac-
tion in the mandibular arch in Class II treatment.
For example, in Class II therapy with four premo-
lar extractions, power ridges should be consid-
ered on the mandibular incisors to maintain
torque during protraction of the mandibular pos-
terior teeth.
ingually Displaced Maxillary Lateral

L
Incisors
Fig. 8.1 Power ridges or pressure lines have been incor-
porated into the aligner on the facial surfaces near the gin-
gival margins for the mandibular incisors. The power Lingually displaced maxillary lateral incisors are
ridges are employed for supplementing lingual root torque typically inclined with their roots excessively
Fig. 8.2 The incorporation of power ridges can be beneficial in correcting excessively lingualized incisors. They are
also important in preventing over-retraction of incisors when lingualization is planned
lingual. Therefore, these lateral incisors require sure line in the linguocervical area of the
significant facial root torque for ideal position- displaced maxillary lateral incisor with a 3 mm
ing. Though it has been shown that incisor labial horizontal dimple plier. This pressure line can be
root torque is more accurate than lingual root incorporated for a series of aligners until the
torque with clear aligners, it is likely significant desired amount of facial root torque has been
labial root torque will require the use of adjuncts achieved.
to achieve the desired movement [3]. In the However, in the uLab aligner system, pressure
Invisalign system, supplementing facial root lines and pressure points are freely manipulated
torque is problematic because power ridges can by the clinician. In this case, for a lingually dis-
only be placed on the facial surfaces of either placed maxillary lateral incisor, the clinician can
maxillary or mandibular incisors. An alternative prescribe a pressure line on the linguocervical
solution can be to manually alter aligner geome- area and a pressure point on the facial surface
try. Specifically, the clinician can create a pres- near the incisal edge. This arrangement will allow
Fig. 8.3 The incorporation of power ridges is essential of treatment to maintain torque during incisor retraction
for maintaining torque during significant incisor retrac- for space closure and achievement of ideal overjet.
tion. For patient K.C., power ridges were placed on the Superimpositions of initial and final tooth positions show
maxillary and mandibular incisors throughout the course significant maxillary and mandibular incisor retraction
Fig. 8.4 In deep bite cases with significant incisor retrac- and control of incisor inclination. In the treatment of deep
tion, requiring control of incisor torque, anterior intrusion bite cases, overbite is routinely overcorrected for more
may be programmed with power ridges for bite opening predictable overbite reduction
Fig. 8.5 The placement of power ridges assists in main- mandibular incisors allowed for torque control during sig-
taining anterior torque during protraction of posterior nificant mandibular posterior protraction
teeth. For patient X.W., placement of power ridges on the
for the generation of greater coupling moments compensatory changes and to facilitate surgi-
and improve the accuracy of the facial root torqu- cal correction. For example, prior to Class III
ing movement. surgical correction, typically with a mandibu-
lar setback, the maxillary and mandibular inci-
sor inclinations usually must be normalized.
Dental Decompensation The mandibular incisors, which are typically
for Orthognathic Surgery retroclined in Class III malocclusions, must be
significantly advanced into normal inclination.
Dental decompensation is frequently needed In these cases, the incorporation of power
prior to orthognathic surgery in combined sur- ridges would be beneficial for achieving the
gical and orthodontic treatment. One of the planned lingual root torque of the mandibular
significant components of decompensation is incisors during presurgical dental decompen-
the calibration of incisor inclination to undo sation (Fig. 8.6).
Fig. 8.6 Power ridges can be incorporated for controlling enhancing lingual root torque to normalize incisor inclina-
torque during surgical decompensation. For patient L.M., tions prior to a BSSO mandibular setback
power ridges were placed on the mandibular incisors for
Intermaxillary Forces rather than indiscriminately prescribing power

ridges throughout the entire treatment to avoid
Power ridges and pressure lines can also be use- undesired tooth movements, such as excessive
ful in controlling the adverse effects of intermax- incisor proclination (Fig. 8.7c).
illary elastics on incisors. For example, the heavy
use of Class III elastics can result in unfavorable
lingualizing forces on the mandibular incisors. In The Efficacy of Power Ridges
these circumstances, to counter this effect, the
clinician should consider the incorporation of Certain in vitro studies have argued that the effi-
power ridges on the mandibular incisors to sup- cacy of power ridges may be compromised by
plement lingual root torque. Conversely, in cases the nature of the clear aligner appliance [8]. In
involving the heavy use of Class II elastics, the particular, Hahn et al. showed that because align-
clinician should consider supplementing labial ers tend to “lift up” during torquing movements,
root torque on the mandibular incisors, either the incisor edge will not remain in close contact
with pressure lines when available or the manual with the aligner surface [8]. This biomechanical
alteration of aligner geometry. phenomenon limits the production of an effec-
tive force couple for root movement and sup-
ports the need for overcorrection. It has also
Distalization in Class II Treatment been postulated that the distortion of the aligner
during the torquing movement causes an unde-
Power ridges are also important in controlling sired intrusive effect [9]. Nevertheless, these
maxillary incisor torque with Class II division 1 in vitro studies have also concluded that
cases treated non-extraction with significant improved root control might be achievable for
maxillary arch distalization. The power ridges incisors with the use of attachments and altera-
should be considered because of the significant tions in aligner geometry [10].
retraction involved (Fig. 8.7a, b). It is important Although no clinical trials have rigorously
to note that during Clincheck design, the clini- evaluated the efficacy of power ridges for pro-
cian should be mindful in only prescribing the ducing root torque, case studies have shown an
number of stages of power ridges necessary, average of 55–70% of requested lingual root
The Efficacy of Power Ridges 133
Fig. 8.7 (a, b) Power ridges should be incorporated for torque during the entire duration of the first course of
maxillary incisors within normal inclination or that are aligners. (c) Power ridges can be requested for a specific
lingualized during significant retraction. For patient K.W., number of stages rather than the entire treatment to con-
who presented with a Class II div II malocclusion and trol the amount of lingual root torque and prevent exces-
severe deep bite, power ridges were placed on the maxil- sive incisor proclination
lary central incisors during retraction for lingual root
torque achieved with the incorporation of power References

ridges [11]. Our clinical findings have shown
comparable results of approximately 1° of procli- 1. Sfondrini MF, Gandini P, Castroflorio T, et al.
Buccolingual inclination control of upper central
nation achieved with 2–3 stages of power ridges. incisors of aligners: a comparison with conven-
Clinicians should be mindful of this margin of tional and self-ligating brackets. Biomed Res Int.
error and consider overcorrection when prescrib- 2018;2018:9341821.
ing power ridges, especially in cases requiring 2. Haouili N, Kravitz ND, Vaid NR, Ferguson DJ,
significant root torque. tive follow-up study on the efficacy of tooth move-
Torque control can be enhanced by combin- ment with Invisalign. Am J Orthod Dentofac Orthop.
ing pressure lines and pressure points on the 2020;158(3):420–5.
incisal region of the opposing surface (as dis- 3. Jiang T, Jiang YN, Chu FT, Lu PJ, Tang GH. A cone-
beam computed tomographic study evaluating the
cussed in Chap. 1). For example, lingual root efficacy of incisor movement with clear aligners:
torque can be enhanced by placing the power assessment of incisor pure tipping, controlled tip-
ridge on the labial surface near the gingival mar- ping, translation, and torque. Am J Orthod Dentofac
gin of a mandibular incisor in addition to a pres- Orthop. 2021;159(5):635–43.
4. Pan HY, Yang H, Zhang R, Yang YM, Wang H, Hu
sure point on the lingual surface near the incisal T, et al. Use of cone-beam computed tomography
edge. Currently, unlike the uLab software which to evaluate the prevalence of root fenestration in a
allows for the free manipulation of pressure Chinese subpopulation. Int Endod J. 2014;47:10–9.
lines and pressure points, the Invisalign system 5. Simon M, Keilig L, Schwarze J, Jung BA, Bourauel
C. Forces and moments generated by removable ther-
does not allow the clinician placement of either moplastic aligners: incisor torque, premolar derota-
power ridges or pressure points. Pressure points tion, and molar distalization. Am J Orthod Dentofac
would have to be manually incorporated with Orthop. 2014;145(6):728–36.
dimple pliers when not automatically placed by 6. Simon M, Keilig L, Schwarze J, Jung BA, Bourauel
the software. technique--regarding incisor torque, premolar dero-
2014;14:68.
Controlling Torque with Clear 7. Dai FF, Xu TM, Shu G. Comparison of achieved and
Aligners and central incisors: first premolar extraction treatment
The incorporation of power ridges is essential 8. Hahn W, Zapf A, Dathe H, Fialka-Fricke J, Fricke-
for improving torque control during clear Zech S, Gruber R, Kubein-Meesenburg D, Sadat-
Khonsari R. Torquing an upper central incisor with
aligner treatment. Clinical and in vitro trials aligners--acting forces and biomechanical principles.
have shown the adjunct’s efficacy in enhancing Eur J Orthod. 2010;32(6):607–13.
the accuracy of root movement. Planned torque 9. Brezniak N. The clear plastic appliance: a biomechan-
is frequently not achieved, likely due to the ical point of view. Angle Orthod. 2008;78(2):381–2.
10. Bollen AM, Huang G, King G, Hujoel P, Ma
nature of the clear aligner appliance and the dif- T. Activation time and material stiffness of sequential
ficulty of root movement. Because of this mar- removable orthodontic appliances. Part 1: ability to
gin of error, torque control remains a major complete treatment. Am J Orthod Dentofac Orthop.
liability in clear aligner therapy. Consequently, 2003;124(5):496–501.
11. Boyd R. How successful is Invisalign for treatment
the clinician should consider the judicious use of anterior open bite and deep overbite? American
of adjunctive strategies for significant torquing Association of Orthodontics. 2013. https://www.aao-
movements and torque control, including pres- info.org/system/files/media/documents/Boyd,Robert
sure lines, pressure points, manual alteration of %2D%2DTreatmentofDeepandOpenbitewithClearAl
igners.pdf. Accessed 13 Jun 2021.
aligner geometry, and overcorrection.
Overcoming Limitations
in Extraction Therapy
9
Contents
How Predictable Is Extraction Therapy with Clear Aligners? 135
Treatment Planning Considerations for Predictable Extraction Therapy 136
Clincheck Development for Extraction Therapy 136
Clinical Management of Extraction Therapy 142
Improving the Efficacy of Clear Aligner Extraction Therapy 146
References 146
ow Predictable Is Extraction
H adjacent to extraction spaces for supplementing
Therapy with Clear Aligners? posterior anchorage and optimized attachments
on canines to improve the bodily retraction of
Extraction therapy remains one of the most for- canines. Also, the protocol introduced aligner
midable challenges for clear aligners. Clinical tri- activations or specific force systems to reduce
als and case reports have shown that extraction undesired tipping and incisor extrusion during
cases with clear aligners often do not achieve pre- retraction. Early clinical trials have shown greater
dicted outcomes [1]. Notably, teeth adjacent to accuracy with G6-optimized attachments in con-
premolar extraction spaces tend to tip signifi- trolling the mesial translation of first molars
cantly during space closure. Also, in first premo- when compared to conventional vertical attach-
lar extraction cases, clear aligners have ments [2]. Other clinical trials have also sug-
demonstrated poor incisor torque control, charac- gested similar effectiveness as measured by ABO
terized by greater lingual tipping than pro- scores between clear aligners and fixed appli-
grammed for the maxillary incisors [2]. ances in four premolar extraction cases after the
Anchorage loss and poor incisor torque control G6 modifications, though the clear aligner cases
constitute two of the major limitations of extrac- typically required longer treatment times with
tion therapy with clear aligners. courses of refinement [3].
In 2015, Invisalign introduced the G6 protocol For extraction therapy with clear aligners,
to improve the efficacy of extraction therapy strategic treatment planning and Clincheck devel-
(Fig. 9.1). Specifically, the protocol incorporated opment and the judicious use of adjuncts and
optimized attachments on premolars and molars auxiliaries such as power ridges and partial fixed
https://doi.org/10.1007/978-3-030-92810-0_9
136 9 Overcoming Limitations in Extraction Therapy
Fig. 9.1 For patient Z. L., we designed a four premolar retraction attachments on all four canines allegedly sup-
extraction pattern to decrowd the maxillary and mandibu- plement bodily movement during retraction, while the
lar arches and to reduce the significant overjet. Invisalign’s optimized moderate anchorage attachments on the premo-
G6 attachments were placed in all four quadrants for lars and molars supposedly enhance posterior anchorage
space closure with moderate anchorage. The optimized during space closure
appliances are essential for ideal outcomes. The Studies have shown a trend for greater tipping of
careful planning of incisor retraction and space mandibular teeth into extraction spaces when
closure with adjunctive measures such as virtual compared to that of maxillary teeth [1]. Therefore,
gable bends can minimize undesired tooth move- it would be prudent for the clinician to consider
ments. The incorporation of auxiliaries such as a atypical extraction patterns instead of four premo-
course of partial fixed appliances can be applied lar extractions. Commonly, an atypical pattern of
either during or after clear aligner therapy to extraction such as the extraction of maxillary pre-
assist in achieving planned movements by molars and IPR or the extraction of a mandibular
uprighting tipped teeth adjacent to extraction incisor can be a viable alternative for the treatment
sites [4]. Anchorage management can also be of crowding in the mandibular arch. An atypical
supplemented with intermaxillary elastics and extraction pattern can often minimize the adverse
auxiliary miniscrews. effects of conventional four premolar extractions,
In this chapter, we describe the current limita- including excessive tipping of teeth adjacent to
tions of extraction therapy with clear aligners. extraction sites, lateral open bites, and loss of
We then discuss both current and prospective torque in the mandibular incisors (Fig. 9.3).
approaches in treatment planning and mechano- Therefore, the clinician should plan for two pre-
therapy for their management. molar extractions in the mandibular arch, along
with extractions of two maxillary premolars, only
when truly necessary.
reatment Planning Considerations
T
for Predictable Extraction Therapy
Clincheck Development
Premolar extractions in the mandible are usually for Extraction Therapy
more challenging than those in the maxilla, most
likely due to resistance to bodily movement from Tipping During Space Closure
the greater density of the mandible [5]. As a result,
significant undesired tipping can occur in the teeth In Clincheck development for extraction ther-
adjacent to extraction sites in both arches, often apy, it is important to judiciously plan space
with greater severity in the mandible (Fig. 9.2) [6]. closure to minimize adverse effects, especially
Fig. 9.2 Excessive tipping tends to occur with more Excessive tipping in the mandible can be avoided or mini-
severity in teeth adjacent to mandibular extraction sites mized with treatment planning for atypical extractions
compared to those adjacent to maxillary extraction sites. and careful virtual setups of extraction space closure
excessive tipping in the teeth adjacent to the root torque for incisors during retraction [2].
extraction space. One of the current limitations The clinician should be mindful that the appli-
of available clear aligner software is that they cation of anterior lingual root torque will
do not allow the clinician to visualize the move- result in a reciprocal mesial tipping force for
ments produced by virtual gable bends (VGB). the first molar [7]. As a result, the clinician
As a result, the clinician can only approximate should consider overcorrecting distal crown
the predicted effects of the VGB. Ideally, clear tip, analogous to a tip-back bend in fixed
aligner software should display the precise appliances. Studies have suggested that over-
movements created by the VGB so the clinician correcting the distal tip of first molars in addi-
can adjust its staging. At present, the clinician tion to attachment use during space closure
can only request a certain number of stages of might help counteract a mesial tipping force
VGB, with an arbitrary amount of movement and maintain tooth angulation for more bodily
produced in each stage. Nevertheless, the clini- tooth movement.
cian should ensure that the VGB has been Ideally, excessive tipping and associated
incorporated during extraction space closure to adverse effects including lateral open bite could
prevent excessive tipping and to achieve root be controlled through the incorporation of pres-
parallelism. sure points or power ridges on the lingual sur-
In addition to the VGB, the clinician should faces of posterior teeth. Early studies have
consider overcorrection of root movement to demonstrated that the G6 optimized attachment
prevent excessive crown tipping (Fig. 9.4). showed improved resistance to mesial tipping of
The overcorrection can be requested along maxillary molars compared to conventional
with the VGB. Overcorrection during extrac- attachments [2]. Opposing pressure points could
tion therapy has been advocated for move- enhance G6 optimized attachments to produce a
ments challenging for aligners, such as body coupling effect and more bodily translation
movement during space closure and lingual (Fig. 9.5).
Fig. 9.3 In patient K.J., an atypical extraction pattern of loss of torque in the mandibular incisors. Nearly ideal root
two maxillary first premolars and IPR in the lower arch parallelism was achieved, as shown by the final panoramic
allowed for avoiding adverse effects, such as lateral open radiograph
bite, excessive tipping of mandibular posterior teeth, and

Fig. 9.4 For patient N.P., an implant space for the man- teeth. However, a VGB was not incorporated in the first
dibular left canine was required, as the mandibular left course, leading to excessive tipping of both teeth and poor
canine was planned to substitute the congenitally missing root parallelism. In a 12-month refinement course, a VGB
left mandibular lateral incisor. In the first course of align- in addition to overcorrection of root movement was incor-
ers, which lasted 10 months, the mandibular left canine porated to separate the roots. The addition of the VGB and
was mesialized, while the mandibular left first premolar overcorrection of root movement allowed for full separa-
was distalized to create an implant space between the two tion of the canine and premolar roots
Controlling Posterior Torque
Controlling buccolingual inclination of the poste-

rior teeth is essential for achieving proper poste-
rior interdigitation, ideal buccal overjet, and
preventing occlusal interferences. Commonly,
the posterior teeth exhibit inadequate buccal root
torque, resulting in plunging palatal cusps, occlu-
sal interferences, and lateral open bites. To
achieve proper posterior buccolingual inclina-
tion, the clinician should ensure in the virtual
setup that the arches are sufficiently expanded
and the posterior maxillary molars have adequate
buccal root torque [4].
Invisalign’s G8 modifications have suppos-
edly improved the application of buccal root
torque during posterior expansion through opti-
Fig. 9.5 Ideally, a pressure point could be incorporated mized expansion attachments and specific con-
on the lingual surfaces of the posterior teeth near their
touring in aligner surfaces [9]. However, the
occlusal tables. The pressure point’s buccal force can
oppose the lingual force created by the G6 attachment to efficacy of the G8 modifications has not been rig-
produce a couple. This couple would allow for more orously evaluated and they are frequently not
bodily translation of posterior teeth during space closure triggered in extraction cases (G8 activation is
only triggered when a specific amount of expan-
Considerations for Posterior sion has been programmed). Ideally, aligner acti-
Protraction vation should be default whenever significant
buccal root torque is programmed. Likewise,
One of the most important considerations during power ridges or pressure points should be made
Clincheck development is the amount of p osterior available for posterior teeth to supplement buccal
protraction during space closure. If the posterior root torque in the Invisalign software, although
teeth are planned for significant protraction, such they can be currently incorporated in the uLab
as >3 mm, then the clinician should anticipate software (Fig. 9.6).
excessive crown tipping, lateral open bite, and
loss of incisor torque. During extraction therapy,
the greater the amount of planned translation, the ontrolling Incisors During
C
greater the likelihood for crown tipping. This is Retraction
supported by clinical trials which have shown
that extraction therapy in cases with greater One of the primary challenges of extraction ther-
crowding showed less translation and less mesial apy is controlling incisor torque and vertical
tipping of first molars [2]. It has also been dem- position during retraction. Incisors tend to dem-
onstrated that less anchorage loss is correlated onstrate greater lingual tipping than programmed
with greater severity of initial crowding [8]. In leading to over-retraction and deep overbites [2].
crowded arches, the extraction space is predomi- Often, the clinician will have to overcorrect the
nately used for relieving crowding and anterior planned intrusion of the maxillary incisors to
retraction instead of posterior protraction. The prevent excessive bite deepening (Fig. 9.7). This
clinician should be cautious in planning for is in accordance with recommendations from
extraction therapy involving significant posterior studies which have suggested overcorrection to
protraction and consider a non-extraction improve the efficacy of anterior intrusive move-
approach to avoid adverse effects. ments [10]. As discussed in Chap. 6, overcorrec-
software is the lack of integration of cephalomet-

ric data into the virtual setup. This would greatly
improve the accuracy of treatment planning inci-
sor movements, especially for both torque and
vertical position (Fig. 9.8).
linical Management of Extraction

C
Therapy
Frequency of Aligner Changes
Invisalign has suggested that 7-day aligner

changes are viable for successful clinical out-
comes and shorter treatment times [11]. However,
studies have contested this claim and have shown
that complex movements such as distal crown
tipping, buccal-crown torque, and mandibular
posterior intrusion were more accurate with
14-day aligner changes when compared to both 7
and 10-day aligner changes [12]. Early studies
also demonstrated that patients with 14-day
Fig. 9.6 Ideally, the incorporation of a power ridge or
pressure point on the lingual surfaces of posterior teeth
aligner changes were more likely to complete a
near their cervical areas can supplement buccal root course of aligners compared to those changing
torque during extraction therapy. However, at present, the aligners weekly [13]. Considering the complex-
Invisalign software does not allow a power ridge or pres- ity of the movements involved in extraction ther-
sure point placement on lingual surfaces or on posterior
teeth (though the uLab software does offer these options).
apy, which include significant posterior crown
It is important to confirm in the software that posterior tipping and torquing, 14-day aligner changes are
teeth have adequate buccal root torque to prevent plunging recommended for accurate tooth movement. This
palatal cusps, occlusal interferences, and lateral open bites 14-day regimen would be especially recom-
mended for adults, whose velocity of orthodontic
tion of intrusion for the incisors will often result tooth movement has been shown to be slower
in a final simulated overbite that appears shallow. than that of children [14].
The incorporation of power ridges in extraction
arches should also be considered, especially if
initial incisor inclinations are within normal Tipping During Therapy
range or retroclined. Studies have also advocated
overcorrecting lingual root torque for incisors Commonly, the teeth adjacent to the extraction
during the virtual setup for torque control. site will excessively tip during the course of ther-
In patients who initially present with exces- apy and manifest as poor tracking with the
sively deep overbites and vertical maxillary aligner. In these cases, the clinician can consider
excess, the use of anterior TADs should be con- extending wear time for the patient on the poorly
sidered to supplement maxillary incisor intrusion tracking aligner to allow for more movement on
and to avoid bite deepening during incisor retrac- the tipped teeth toward their programmed posi-
tion (Fig. 9.7). tions. The clinician can also incorporate pressure
One of the limitations in controlling incisors points with hand instruments onto the aligner in
during extraction therapy with the various current problematic areas for improved tracking and
Fig. 9.7 In patient W.W., a clinician extracted maxillary intrusion and lingual root torque on the maxillary incisors.
first premolars with poor torque control of the maxillary The clinician also planned for a final bite that was exces-
incisors during retraction. As a result, there was a signifi- sively deep. To minimize the gingival display, TADs will
cant loss of incisor torque, as shown by the progress ceph- be placed distal to the maxillary lateral incisors for an
alometric radiograph. The loss of torque also led to incisor intrusive force. The incisors will have to be torqued and
extrusion, bite deepening, and an unesthetic increase of significantly intruded to aid in bite opening
gingival display. The clinician planned for inadequate
encapsulation. For example, dimples can be Combination Treatment

placed in the cervical area of the aligner to
improve retention for an excessively tipped The timely intervention with combination treat-
molar. Importantly, addressing poor tracking dur- ment is essential for successful outcomes and
ing the course of aligners can minimize the dura- minimizing treatment times in clear aligner
tion of refinement and the need for auxiliaries, extraction therapy. Frequently, excessively tipped
including partial fixed appliances. teeth adjacent to extraction sites will require aux-
iliary methods for uprighting. The clinician

should consider either partial braces or metal but-
tons for vertical elastics prior to a course of
refinement (Fig. 9.9) [6]. After the posterior
crowns have been significantly uprighted, a
refinement course can be employed for additional
detailing and finishing. A comparison between
fixed appliances and clear aligners in the treat-
ment of first premolar extraction cases showed
comparable efficacy but as much as 7 months of
refinement for cases treated with clear aligners
[3]. This method of timely combination treatment
can more predictably upright tipped crowns and
Fig. 9.8 At present, no software has fully integrated
cephalometric data with teeth movement. Ideally, clear lessen the duration of the refinement course and
aligner software should allow for projections of cephalo- overall treatment time.
metric changes over the course of treatment. This integra-
tion would allow for more precise planning of incisor
movements in all dimensions
Fig. 9.9 The addition of an auxiliary at the end of the first sion cut on the right mandibular second premolar). After
course of aligners during extraction therapy can correct 3 months of vertical elastic wear, the molar was extruded
tipped posterior teeth in an efficient manner. For this into ideal inclination and proper interdigitation prior to a
patient, a button was bonded on the maxillary right molar refinement for detailing and finishing
for vertical elastics to the opposite arch (usually a preci-
I mproving the Efficacy of Clear appliances in first-premolar extraction cases. J Clin

Orthod. 2020;52(5):294–301.
Aligner Extraction Therapy 4. Bowman SJ, Celenza F, Sparaga J, Papadopoulos
MA, Ojima K, Lin JC. Creative adjuncts for clear
Recent studies have suggested improved efficacy aligners, part 3: extraction and interdisciplinary treat-
for extraction therapy with clear aligners due to ment. J Clin Orthod. 2015;49(4):249–62.
5. Devlin H, Horner K, Ledgerton D. A comparison of
the G6 protocol and the use of auxiliaries [15]. maxillary and mandibular bone mineral densities. J
However, the method is still limited by major lia- Prosthet Dent. 1998;79(3):323–7.
bilities during space closure and anterior teeth 6. Zhu Y, Li X, Lai W. Treatment of severe anterior
retraction, which can result in loss of anterior crowding with the Invisalign G6 first-premolar extrac-
tion solution. J Clin Orthod. 2019;53(8):459–69.
torque, deepening of overbite, excessive tipping 7. Tuncay O, Bowman SJ, Amy B, Nicozisis J. Aligner
of teeth adjacent to extraction sites, and poor pos- treatment in the teenage patient. J Clin Orthod.
terior interdigitation. These sequelae can be mini- 2013;47:115–9.
mized or avoided through treatment planning in 8. Geron S, Shpack N, Kandos S, Davidovitch M,
Vardimon AD. Anchorage loss--a multifactorial
view of the appliance’s typical behavior with response. Angle Orthod 2003;73(6):730–37.
extraction therapy, judicious planning of incisal 9. Align Technology. Align Technology announces
and molar movements during the virtual setup, Invisalign G8 with new Smartforce aligner activa-
and timely treatment modification, with auxilia- tion features. 2020. https://investor.aligntech.com/
ries as necessary, during the course of therapy. announces-invisalign-g8-new-smartforce. Accessed
These methods aim at improving the predictabil- 25 Jul 2021.
ity of movements during extraction therapy and 10. Haouili N, Kravitz ND, Vaid NR, Ferguson DJ,
therefore minimizing adverse effects. It is evident Makki L. Has Invisalign improved? A prospec-
tive follow-up study on the efficacy of tooth move-
the future of clear aligner extraction therapy lies ment with Invisalign. Am J Orthod Dentofac Orthop.
in innovating its biomechanical features, whether 2020;158(3):420–5.
within the aligner material or its auxiliaries, for 11. Fry R. Weekly aligner changes to improve
producing more ideal force systems for more Invisalign treatment efficiency. J Clin Orthod.
2017;51(12):786–91.
accurate movements. 12. Al-Nadawi M, Kravitz ND, Hansa I, Makki L,
Ferguson DJ, Vaid NR. Effect of clear aligner wear
protocol on the efficacy of tooth movement. Angle
Orthod. 2021;91(2):157–63.
References 13. Bollen AM, Huang G, King G, Hujoel P, Ma
T. Activation time and material stiffness of sequential
1. Baldwin DK, King G, Ramsay DS, Huang G, Bollen removable orthodontic appliances. Part 1: ability to
AM. Activation time and material stiffness of sequen- complete treatment. Am J Orthod Dentofac Orthop.
tial removable orthodontic appliances. Part 3: premo- 2003;124(5):496–501.
lar extraction patients. Am J Orthod Dentofac Orthop. 14. Dudic A, Giannopoulou C, Kiliaridis S. Factors
2008;133(6):837–45. related to the rate of orthodontically induced
2. Dai FF, Xu TM, Shu G. Comparison of achieved and tooth movement. Am J Orthod Dentofac Orthop.
predicted tooth movement of maxillary first molars 2013;143(5):616–21.
and central incisors: first premolar extraction treatment 15. Gaffuri F, Cossellu G, Lanteri V, Brotto E, Farronato
with Invisalign. Angle Orthod. 2019;89(5):679–87. M. Comparative effectiveness of Invisalign and fixed
3. Gaffuri F, Cossellu G, Lanteri V, Brotto E, Farronato appliances in firstpremolar extraction cases. J Clin
M. Comparative effectiveness of Invisalign and fixed Orthod. 2020;52(5):294–301.
The Predictability of Bite Jumps
10
Contents
What Are Bite Jumps? 147
Indications for Bite Jumps 148
Principles of Bite Jump Use 152
Controversial Uses of the Bite Jump 154
olutions for Discrepancies Between Clinical Outcomes and Outcomes
S
Predicted by Bite Jumps 158
Optimal Planning of Bite Jumps in Clear Aligner Treatment 160
References 161
What Are Bite Jumps? setup or request a bite jump during the develop-
ment of the setup.
Bite jumps constitute a significant feature of The most common issues associated with bite
virtual setups for the treatment of complex jumps are its proper indications and its timing for
malocclusions. The bite jumps simulate exten- use during therapy. During the virtual setup, the
sive movements in the maxilla, mandible, or a bite jump should be considered as a projected
combination, resulting in changes in maxillo- change in skeletal relationships in the anteropos-
mandibular relationships. These include large terior, vertical, or transverse dimensions. The pri-
anteroposterior movements, rotation of the mary indications for the bite jump include
maxilla or mandible for anterior open bite clo- growing patients in which the clinician antici-
sure, and rotation of the maxilla or mandible pates significant jaw growth, open bite closure
about a vertical axis for the correction of asym- involving mandibular autorotation, and cases
metries. Currently, the Invisalign software pos- involving orthognathic surgical correction. The
sesses the most developed bite jump feature use of the bite jump to project unrealistic move-
among available software for anteroposterior, ments such as extensive space closure or signifi-
vertical, and transverse movements in either the cant Class II correction in the absence of a
maxilla or mandible. The clinician can select the functional regulator or growth can result in the
bite jump in the prescription form for the virtual planning of unachievable dental and jaw move-
ments and an inaccurate virtual setup.
https://doi.org/10.1007/978-3-030-92810-0_10
148 10 The Predictability of Bite Jumps
The bite jump can be incorporated as a sin- Table 10.1 The common indications and contraindica-
tions for the use of the bite jump
gle stage or as a series of stages for incremen-
tal skeletal movements. Typically, a single Indications Contraindications
stage is employed to simulate open bite closure Growing patients Correction of excessive overjet
without adequate
or surgical correction, though the precise tim- mechanotherapy
ing of open bite closure in nonsurgical treat- Mandibular Extraction space closure
ments can be difficult to predict. Multiple autorotation during
incremental stages would be applicable for open bite closure
Orthognathic surgery TAD-assisted movements
treatment with a functional regulator, such as
Dental functional shift Extensive space closure
the MA appliance. This setup would simulate
the effects of traditional functional appliances,
which have shown greater short-term gains in late both the significant forward movement of
Class II correction with incremental mandibu- the maxilla and the jumping of the anterior
lar advancement when compared to maximal crossbite (Fig. 10.1).
mandibular advancement [1]. A shorter series Similarly, a Class II patient can be treated with
of stages can also be incorporated to simulate a combination approach consisting of clear align-
maxillary arch distalization with a distalizing ers and a Class II orthopedic appliance, such as
appliance. the cervical headgear. This form of therapy would
In this chapter, we describe the major indica- also require a bite jump to simulate the forward
tions, contraindications, and principles for the growth of the mandible during treatment. The
use of the bite jump in virtual setups for accurate incorporation of the bite jump would allow for a
treatment planning and predictable outcomes. We more realistic representation of the Class II cor-
will also consider their application in both grow- rection (Fig. 10.2). When planning for a bite
ing and nongrowing patients, as well as in cases jump, the clinician should also consider the
involving functional regulators, orthopedic appli- amount of growth remaining with growth indica-
ances, distalizing appliances, and orthognathic tors frequently used for the treatment of Class II
surgery. malocclusions, such as the hand and wrist matu-
ration method, standing height, and the cervical
vertebrae maturation method (CVM) [2]. For
Indications for Bite Jumps Class II patients with little to no growth remain-
ing, a bite jump simulating significant forward
Growing Patients movement of the mandible would be contraindi-
cated (unless the clinician were planning for a
One of the most essential indications for bite surgical correction).
jumps is the realistic simulation of skeletal Importantly, in Phase I treatment with grow-
growth in growing children and adolescents ing patients, the bite jump would also be indi-
(Table 10.1). The bite jump is frequently indicated for Class II and Class III patients treated
cated for Phase I treatment with clear aligners, with clear aligners and intermaxillary elastics
or Invisalign First, as these patients are certain (without an orthopedic appliance). Though it has
to experience significant jaw growth during been shown that the effects of intermaxillary
treatment. In particular, the bite jump should be elastics are primarily dentoalveolar, a bite jump
prescribed for growing Class II or Class III would still be indicated because the growing
patients to predict anteroposterior orthopedic patient will predictably experience significant
changes. For example, as discussed in Chap. 2, mandibular growth [3]. The clinician can pro-
a Class III patient can be treated with a combi- gram the bite jump to simulate jaw growth during
nation approach consisting of clear aligners and therapy (Fig. 10.3).
RPFM for maxillary protraction. The incorpora- In patients treated with clear aligners and the
tion of a bite jump would be necessary to simu- mandibular advancement feature, the bite jump
Fig. 10.1 For patient A.P., a bite jump was planned for stage 29 to represent forward movement of the maxilla through
growth and orthopedic maxillary protraction with RPFM
Fig. 10.2 The orthopedic treatment of Class II malocclu- mandible. In patient M.S., cervical headgear supple-
sion in a growing patient can be simulated using continu- mented a distalizing force to the maxillary arch for Class
ous bite jumps to represent the forward growth of the II correction
Fig. 10.3 For patient O.S., the incorporation of a bite aligners. Class II correction was also supplemented with
jump on stage 37 simulates Class II correction from pre- Class II elastics
dicted mandibular growth during the initial course of
is necessary to set up the mandibular forward Open Bite Closure

position. As discussed in Chap. 3, the MA appli-
ance is more likely to produce skeletal effects in Studies on open bite treatment with clear aligners
patients during the pubertal peak as compared to have demonstrated that bite closure occurs
those in a prepubertal stage [4]. The bite jump through a combination of incisor extrusion, molar
must be incorporated in the virtual setup for the intrusion, and counterclockwise rotation of the
MA appliance, usually in 2 mm advancements mandible [5]. A bite jump would be indicated to
of the mandible until an edge-to-edge position realistically model the autorotation of the man-
(or an overcorrected position), though the exact dible. In most cases of open bite treatment, the
amount of advancement can be adjusted by the virtual setup will show intrusion of the posterior
clinician. teeth, extrusion of the maxillary and mandibular
incisors, and a bite jump simulating autorotation Principles of Bite Jump Use
and anterior open bite closure toward the end of
therapy. Predictability of the Bite Jump
When prescribing bite jumps, the clinician should

Orthognathic Surgery confirm that the planned dental and skeletal
movements are likely to occur. If there is a high
The significant jaw movements in orthognathic degree of uncertainty regarding the movements
surgery should be modeled with a bite jump at represented by a bite jump, then it should be
the end of the presurgical course of therapy. It avoided in the virtual setup. Conceptually, the
is recommended that the clinician coordinate bite jump should be considered as a simulation of
the design of the bite jump with the attending skeletal movements of either the maxilla, mandi-
surgeon for a definitive treatment plan and the ble, or a combination. An exception would be the
planning of presurgical movements that will correction of a functional shift, whose bite jump
optimize the effectiveness of the surgery [6]. would represent dental movements.
For example, the bite jump and the presurgical It is essential to note that the bite jump should
movements will differ significantly for a Class not be employed as an alternative for movements
III patient treated with a mandibular setback that are biomechanically unrealistic. For exam-
and maxillary advancement compared to those ple, if there is excessive overjet remaining at the
for the same patient treated with only a man- end of a virtual setup for a nongrowing patient,
dibular setback. In either case, presurgical then it would be impractical to prescribe a bite
movements would include incisor decompensa- jump to simulate the correction of the overjet.
tion to increase the negative overjet but exact This sort of bite jump would not be indicated if
movements in all dimensions would differ mechanics were not applied to realistically pro-
depending on the type of surgery planned. If the duce significant Class II correction (Fig. 10.4).
patient has a transverse discrepancy severe Recent studies have shown that no anteroposterior
enough to warrant a segmental maxillary sur- improvement was achieved in clear aligner treat-
gery, then a posterior crossbite and midline dis- ments of Class II malocclusion with Class II elas-
crepancy would be left untreated in the tics [7]. Therefore, it is questionable whether
presurgical phase. In contrast, for a single-jaw Class II elastics alone would be able to produce
surgery, a midline discrepancy can be corrected the significant overjet correction predicted by a
in the nonsurgical arch during the presurgical bite jump.
phase [6].
Timing
Dental Functional Shift
For open bite closure, the bite jump is usually
In certain cases, occlusal interferences can result prescribed at the end of the course of aligners in
in functional shifts that manifest in midline devi- the virtual setup. The bite jump can be repre-
ations, posterior crossbites, and other transverse sented as the final stage following the virtual
discrepancies. The bite jump would be indicated maxillary and mandibular first molar-to-first
for such dental functional shifts. Typically, the molar power chains (known as maxillary and
bite jump would be planned at the end of the mandibular virtual C-chains for Invisalign clear
course of aligners on the virtual setup after the aligners). It is difficult to predict when precisely
interference has been relieved through dental open bite closure will occur, so it would be more
movements. judicious to place the bite jump toward the end
Principles of Bite Jump Use 153
Fig. 10.4 Bite jumps should not be used to simulate the correction and overjet reduction without applying mecha-
corrections of large overjet without the application of notherapy to predictably produce these effects. This
adequate Class II mechanotherapy. In this virtual setup, approach would result in discrepancies between predicted
the clinician programmed a highly unrealistic bite jump in and achieved occlusal outcomes
stage 28, in which they simulated both significant midline
of therapy (rather than at the middle or near the In growing patients, the bite jump may need to
beginning of the course of aligners). be incorporated throughout the entire treatment
Nevertheless, we have observed that bite closure to accurately simulate continuous jaw growth
usually occurs in the middle of the course of (Fig. 10.5). In this case, the bite jump would
aligners. The bite jump would also be placed at appear in every aligner stage. This continuous
the end of the virtual setup for a presurgical mode of bite jumps is indicated for Class II ortho-
phase of clear aligner therapy to represent the pedic treatment, Class II and Class III mechanics
surgical correction after all presurgical move- in actively growing patients, and Class III ortho-
ments have been completed. pedic treatment, typically with RPFM.
Fig. 10.5 For growing patients, a continuous bite jump orthopedic maxillary protraction through RPFM was sim-
may have to be incorporated to represent jaw growth. For ulated by a continuous bite jump throughout the initial
patient W. W., the patient’s forward maxillary growth and course of aligners
For the mandibular advancement appliance, distalization of maxillary or mandibular posterior

the bite jump can also be prescribed as incremen- teeth (Fig. 10.6), in ranges of 2–2.5 mm [9]. The
tal changes for gradual forward movement of the bite jump would represent the stages of Class II
mandible. This mode of activation agrees with correction (or Class III correction) during distal-
recent studies that have observed a stepwise ization, showing retraction of the maxillary arch.
mandibular advancement in either fixed or
This scenario would likely require an auxiliary
removable functional appliances allowed for a device, such as a distalizer, to predictably achieve
greater reduction of ANB and greater control of the planned amount of distalization.
incisor proclination compared to single-step
maximum bite jumping [8]. Typically, each bite
jump advances the mandible about 2 mm. But the Controversial Uses of the Bite Jump
clinician can calibrate the precise amount of
mandibular advancement for each bite jump until xcessive Overjet in Nongrowing
E
an edge-to-edge position. Class II Patients
Another less common but viable timing pat-
tern for the bite jump would be a short sequence One of the most common misuses of the bite
of stages in the middle of a course of aligners. jump is its prescription for significant overjet cor-
This pattern would be indicated for significant rection in nongrowing Class II patients in the
Fig. 10.6 A bite jump can be used to simulate the effects of distalization. For patient A.C., the bite jump distalizes the
right maxillary posterior segment by about 1.5 mm
absence of adequate mechanics, such as a func- of the maxillary anterior teeth can be achieved
tional regulator or a distalizer. This application of with supplementary forces from TADs. The cli-
the bite jump is impractical because it represents nician should program overcorrection of the
an unrealistic movement. As a result, the overjet maxillary anterior teeth rather than a bite jump to
correction will likely not be achieved, so that the realistically portray the intrusive movements. An
clinical outcome will significantly deviate from exception would be TAD-supplemented intrusion
the outcome rendered on the virtual setup. of maxillary and mandibular posterior teeth for
This misuse is also commonly observed in open bite closure (Chap. 7). A bite jump would
compromised treatments for adults with severe be indicated to represent the mandibular autoro-
Class II or Class III discrepancies. In these cases, tation, as it is a realistic movement [10].
without a surgical correction or auxiliaries for
Class II correction, it is recommended to avoid
prescription of the bite jump and to develop a Extraction Cases
more realistic virtual setup.
In extraction cases, the bite jump is usually not
indicated, as it may mispresent dental movements
TAD-Assisted Cases and changes in jaw relationships in all dimensions.
As discussed in Chap. 9, the clinician should plan
For movements that are supplemented with TADs, extraction cases with measures such as the G6 pro-
it is more predictable to incorporate overcorrec- tocol to ensure predictable extraction space clo-
tion for the movement rather than a bite jump sure and incisor movements [11]. The extensive
(Fig. 10.7). For example, as discussed in Chap. jaw movements of the bite jump would typically
6, in patients with deep bites and vertical maxil- not occur in extraction cases (except in cases
lary excess, an additional 2–3 mm of intrusion involving mandibular autorotation).
a b c
d e
Fig. 10.7 (a, b) For patient O.L., the left maxillary first necessary to create adequate clearance for the opposing
molar required significant intrusion to create space for an molar restoration. (f, g) A bite jump should not be
opposing implant restoration. A bite jump was not pro- employed to simulate extensive space closure. Instead, clo-
grammed for left maxillary first molar intrusion, as this sure of large spaces should be programmed in a stepwise
would reflect unrealistic tooth movements. (c) Combination fashion for predictability. For patient J.Y., the residual
therapy with partial fixed appliances and a TAD was space between the left maxillary second premolar and left
employed to supplement intrusion, while controlling the maxillary second molar was closed with an initial course
buccolingual inclination of the molar. (d, e) Significant of aligners without the use of a bite jump followed by a
intrusion of the left maxillary first molar was achieved short course of partial fixed appliances in the left maxillary
after six months of treatment. Additional intrusion will be posterior segment to upright the maxillary second molar
Extensive Space Closure first molar space can be supplemented with

braces and a mesializing force from an anterior
The bite jump is rarely indicated for representing anchoring segment of the mandibular first and
the movements involved in extensive space clo- second premolars (Fig. 10.7).
sure. Instead, the clinician should realistically
stage the dental movements, such as the mesial-
ization of a second molar into a first molar space. Mandibular Shifts
Significant space closure may require combina-
tion treatment with fixed appliances. For exam- The bite jump is sometimes indicated for man-
ple, the mesialization of a second molar into a dibular shifts in cases where the resolution of the
Fig. 10.8 For patient F. C., a bite jump was programmed patient’s right, the coordination of maxillary and mandib-
for stage 23 to represent the differential BSSO. The bite ular midlines, and the correction of the left posterior
jump portrays the translation of the mandible to the crossbite
shift can be predictably achieved. For a patient tional shift was caused by a single-tooth anterior
with a mandibular asymmetry treated with a dif- crossbite, as the crossbite would likely be allevi-
ferential BSSO orthognathic surgery, a bite jump ated in the course of aligners.
would be indicated to represent the surgical cor- However, for a patient with skeletal mandibu-
rection (Fig. 10.8). Another viable use of the bite lar asymmetry treated without skeletal correction
jump would be for patients with dental-related in a compromised fashion through methods such
shifts, in which one is certain orthodontic treat- as asymmetrical elastics, a bite jump would be
ment would address the etiology. For example, a contraindicated, as significant skeletal correction
bite jump would be indicated if the dental func- of the asymmetry would not occur.
Solutions for Discrepancies of the mandible will almost always result in

Between Clinical Outcomes heavy anterior interferences and a bilateral poste-
and Outcomes Predicted by Bite rior open bite, which must be closed with a
Jumps refinement course. The MA appliance also
restricts posterior movements due to the presence
Frequently, even with judicious application of the of the precision wings, so the refinement course
bite jump, clear aligner treatments will not will detail posterior teeth positions and their
achieve clinical outcomes as programmed. In occlusion (Fig. 10.9).
these cases, it is necessary to further adjust the
occlusion toward the outcome simulated by the
bite jump, either through refinements or alterna- Orthognathic Surgery Cases
tive methods, such as combination therapy with
fixed appliances. A refinement course usually cannot be avoided
for ideal detailing and finishing in cases involv-
ing orthognathic surgery [12]. An intraoral scan
Growing Patients can be performed during the fourth week follow-
ing the surgery and a course of refinement devel-
For growing Class II and Class III patients, a oped. For more complicated orthognathic surgical
comprehensive course of additional aligners is procedures, such as triple jaw surgery (LeFort I
usually required for detailing and finishing. This osteotomy, sagittal split osteotomy, and genio-
is especially common for patients receiving man- plasty), a refinement course will most likely be
dibular advancement, as the forward positioning required and last longer compared to that of a
Fig. 10.9 In patient A.A, after an initial course of man- terior teeth and commonly results in heavy anterior
dibular advancement, an additional course of refinement interferences. The refinement included the closure of the
was necessary to detail the positions of the posterior seg- bilateral posterior open bites and minimization of heavy
ments. The MA appliance restricts the movements of pos- anterior contacts
Solutions for Discrepancies Between Clinical Outcomes and Outcomes Predicted by Bite Jumps 159

simpler orthognathic surgery. For example, a sur- residual mild anterior open bite, a short course of
gery involving both a segmental maxillary oste- anterior vertical elastics can be considered to
otomy and BSSO would require further achieve proper bite closure.
adjustments to the maxillary arch form and trans-
verse relationships between the maxilla and man-
dible, such as the correction of posterior Dental Functional Shifts
crossbites [6].
Though dental functional shifts are usually
resolved once the etiology is addressed, the
Open Bite Closure occlusion may require further adjustments after
the initial course of aligners to achieve outcomes
Further detailing and finishing will frequently be projected by the bite jump. Specifically, a mid-
required after an initial course of aligners treating line discrepancy may persist despite the allevia-
open bite closure [10]. Clinical outcomes often tion of the shift and the removal of the etiological
do not coincide with the ideal bite closure pro- factor. Minor midline discrepancies can be cor-
jected by the bite jump, although the treatment of rected with an additional course of aligners
mild anterior open bites may result in outcomes incorporating unilateral IPR and a short course of
closer to the projected occlusion, only requiring asymmetric elastics (Fig. 10.10).
minor adjustments. A bilateral posterior open
bite often manifests after anterior open bite clo-
sure due to heavy anterior contacts, intrusive ptimal Planning of Bite Jumps
O
forces in the maxillary and mandibular posterior in Clear Aligner Treatment
segments, and the unpredictability of the skeletal
and dental movements involved in mandibular Bite jumps represent one of the most misused
autorotation [5]. In these cases, the clinician features in the virtual setups for clear aligner
should consider a course of refinement to extrude treatment. The misapplication of the bite jump
the maxillary and mandibular posterior segments. can result in planning for impractical changes in
Alternatively, the clinician can employ auxilia- maxillomandibular relationships and significant
ries, such as buttons on the posterior teeth for discrepancies between projected and clinical out-
vertical elastics wear to achieve proper comes. The guiding principle when considering
interdigitation. the incorporation of the bite jump should be a
Conversely, the initial course of aligners may determination of its predictability—that is, the
result in an anterior open bite that has not been likelihood of the planned jaw movements with
fully closed. As a result, the clinician will have to respect to mechanotherapy and the patient’s den-
incorporate additional bite closure mechanics. tofacial growth. Nevertheless, even when the bite
These can be applied through a refinement course jump is applied in a realistic manner, clinical out-
with additional extrusion of the anterior teeth and comes frequently require further adjustments to
intrusion of the posterior teeth. For cases with a achieve its projections.
References 161
Fig. 10.10 After the correction of a functional shift coordination through asymmetric mandibular IPR and
through the relief of a heavy interference, a mild midline relief of heavy anterior interferences. Afterward, a short
discrepancy may persist. This can be treated with a course of asymmetric elastics (Class II on the left, Class
3–4 month course of asymmetric elastics to ideally coor- III elastics on the right) were worn for 3 months to fully
dinate maxillary and mandibular midlines. For this achieve maxillary and mandibular midline coordination
patient, an initial course of aligners improved midline
References 7. Patterson BD, Foley PF, Ueno H, Mason SA,

Schneider PP, Kim KB. Class II malocclusion cor-
rection with Invisalign: is it possible? Am J Orthod
1. Santana LG, Avelar K, Flores-Mir C, Marques
LS. Incremental or maximal mandibular advance-
8. Knösel M, Espinoza-Espinoza GE, Sandoval-
ment in the treatment of class II malocclusion through
Vidal P, Zaror C. Angle class II correction: step-
functional appliances: a systematic review with meta-
wise mandibular advancement or bite jumping?:
analysis. Orthod Craniofac Res. 2020;23(4):371–84.
a systematic review and meta-analysis of skel-
2. Perinetti G, Contardo L. Reliability of growth indica-
etal, dental and condylar effects. J Orofac Orthop.
tors and efficiency of functional treatment for skeletal
2020;81(4):286–300.
class II malocclusion: current evidence and controver-
9. Ravera S, Castroflorio T, Garino F, Daher S, Cugliari
sies. Biomed Res Int. 2017;2017:1367691.
G, Deregibus A. Maxillary molar distalization with
3. Janson G, Sathler R, Fernandes TM, Branco NC,
aligners in adult patients: a multicenter retrospective
Freitas MR. Correction of class II malocclusion with
study. Prog Orthod. 2016;17:12.
class II elastics: a systematic review. Am J Orthod
10. Harris K, Ojima K, Dan C, Upadhyay M, Alshehri A,
Dentofac Orthop. 2013;143(3):383–92.
Kuo CL, Mu J, Uribe F, Nanda R. Evaluation of open
4. Ravera S, Castroflorio T, Galati F, Cugliari G, Garino
bite closure using clear aligners: a retrospective study.
F, Deregibus A, Quinzi V. Short term dentoskeletal
Prog Orthod. 2020;21(1):23.
effects of mandibular advancement clear aligners in
class II growing patients. A prospective controlled
study according to STROBE guidelines. Eur J
Paediatr Dent. 2021;22(2):119–24.
2019;89(5):679–87.
12. Kankam H, Madari S, Sawh-Martinez R, Bruckman
KC, Steinbacher DM. Comparing outcomes in
Press J Orthod. 2017;22(5):30–8.
orthognathic surgery using clear aligners versus
6. Lou T, Caminiti M. Orthognathic surgery com-
conventional fixed appliances. J Craniofac Surg.
bined with clear aligner therapy. J Clin Orthod.
2019;30(5):1488–91.
2021;55(1):44–58.
Overcoming Limitations
in Finishing
11
Contents
Detailing with Clear Aligner Therapy 163
Intra-arch Occlusal Discrepancies 164
Inter-arch Discrepancies 169
Finishing for Treatment Efficacy 173
References 174
etailing with Clear Aligner

D and lateral incisors and infraerupted lateral inci-
Therapy sors, are resolved by an additional course of
aligners. In such cases, the need to resolve minor
Despite the significant advances to clear aligner occlusal discrepancies often results in a signifi-
therapy since its inception, it is still inhibited by cant increase in treatment time, either in the form
a number of limitations in controlling orthodon- of interrupting a course of aligners or extended
tic tooth movement, many of which manifest in courses of refinement. However, there exist alter-
the finishing stages [1]. Frequently, there is a native methods of modifying aligner material
mismatch between clinical and predicted treat- with hand instruments or incorporating auxilia-
ment outcomes in clear aligner software models ries during a course of aligners to either resolve
[2]. Research has shown that extrusion is the least or improve minor occlusal discrepancies
accurate movement with clear aligner therapy, (Fig. 11.1, Table 11.1). In some cases, tooth
with one study reporting 30% predictability [3]. movement through staging of the aligners and
Rotation was the second least accurate movement attachments may not be adequate to produce the
with clear aligner therapy [1]. A prospective desired tooth movements. Hand instruments,
study analyzing the effects of attachments and allowing for the alteration of aligner geometry,
interproximal reduction on canine movement and auxiliaries like fixed appliances can both
showed a mean accuracy in rotation of 36% [4]. enhance movements difficult for clear aligners.
These inaccuracies in tooth movement often As a result, the clinician can either avert or mini-
manifest as poor tracking for individual teeth mize an additional course of aligners. In this
during the course of therapy. Typically, these manner, the clinician can decrease overall treat-
minor discrepancies, such as unrotated canines
https://doi.org/10.1007/978-3-030-92810-0_11
164 11 Overcoming Limitations in Finishing
problems and allows for increased adaptability

of the appliance for problems that may arise
during treatment.
In this chapter, we start by describing intra-
arch occlusal discrepancies in a variety of dimen-
sions that may arise during the finishing stages
and their solutions. Then we discuss common
inter-arch problems and their treatment with
methods for enhancing the clear aligners through
the incorporation or modification of mechano-
therapy. Lastly, we outline the decision-making
process and timing behind intervention for the
management of discrepancies during the finish-
Fig. 11.1 Hand instruments can enhance the effective-
ness of detailing and finishing by supplementing difficult ing stages.
movements or enhancing mechanotherapy. Their proper
application can minimize or avoid courses of refinement
and shorten overall treatment time Intra-arch Occlusal Discrepancies
Table 11.1 Description of finishing instruments and Discrepancies in the First Order
their indications
Instrument Indication Discrepancies in the buccolingual dimension
1 mm dimple For labialization, derotation, most often manifest themselves in teeth that
plier lingualization and additional
retention. have not derotated as predicted and as a result,
Spacer plier To create space for labial or lingual fail to track with the aligner. Research has
tooth movement and derotation. shown that among the maxillary and mandibular
Eraser plier To remove unwanted attachments or anterior teeth, the maxillary and mandibular
dimples. canines are the least accurate in regards to accu-
3 mm dimple To create power ridges and additional
plier vertical or horizontal attachments.
racy of rotation [4]. Inadequacies in premolar
Bite ramp plier For the addition or modification of rotations have also been observed [5]. Though
bite ramps. we have observed increased accuracy of derota-
Hole punch To create precision cuts and button tion in the maxillary anterior region with recent
plier cutouts. innovations, including Invisalign’s G7 opti-
Precision cut To create precision cuts.
plier
mized attachments for lateral incisor control,
rotational discrepancies still persist and mani-
fest themselves in the late stages of courses of
ment time for more effective orthodontic clear aligners. We note that lateral incisors are
treatment. often unforgiving with patient incompliance.
In the finishing stages, intervention with Nevertheless, we still observe maxillary lateral
hand instruments or auxiliaries during the incisors and maxillary canines that remain
course of aligners can also be applied to inter- rotated despite satisfactory patient compliance
arch discrepancies in a variety of dimensions. (Fig. 11.2).
During treatment, they can be used to enhance For teeth that have not been derotated and
or modify mechanotherapy that did not achieve poorly track with their aligners, the respective
the desired effects or incorporate mechanother- aligner material can be modified with a hand
apy in response to a need that was initially over- instrument to supplement the rotational force
looked. The incorporation of hand instruments supplied by the aligner. Firstly, the non-tracking
and auxiliaries expands the capabilities of the tooth’s adjacent contacts should be verified that
clear aligner to treat complex interocclusal adequate space has been created for derotation.
Fig. 11.2 For patient J. X., the right maxillary lateral

incisor and right maxillary canine failed to derotate com-
pletely after an initial course of aligners
If the contacts are overly tight, the clinician Fig. 11.3 The 1 mm dimple plier (right) can be used to
should create sufficient interproximal space by alter aligner geometry and supplement forces for move-
stripping prior to modifying the aligner mate- ments such as labialization, derotation, or lingualization
rial. After, the aligner material can be modified
with a dimple plier to create a coupled force to suggested that the clinician rescan the patient’s
aid in derotation (Fig. 11.3). Dimples (indenta- occlusion and address the rotational discrep-
tions) should be placed on the mesiolingual and ancy in a mid-course correction or refinement
the distolabial surfaces to create a couple that course. Alternatively, severely rotated teeth
rotates the tooth in a distolingual direction can also be treated with vertical elastics to
(Fig. 11.4a). Conversely, the dimples would be bonded buttons or a combination of sectional
reversed for rotation in the opposite direction. brackets and archwires with clear aligners for a
The dimples should be about 1 mm in diameter short period of time (Fig. 11.5a, b). In this
so that the modified aligner can reseat onto the method, the patient would be maintained on
non-tracking tooth. Slightly larger dimples, the same aligner, usually the final aligner,
such as 3 mm, can be used for additional force while the tooth is adjusted with fixed appli-
to address larger discrepancies. Thirdly, it ances. The aligner would be sectioned to allow
should be noted greater force than usual will be for simultaneous wear of the aligner and the
needed for the patient to seat the aligner because sectional brackets. We have observed that this
it has been slightly deformed. Clinically, one combination type of treatment allows for the
can advise the patient to use a chewie (Fig. 11.4b) correction of rotated anterior teeth with greater
to secure the seating of aligners that have been efficiency than with forces produced solely by
modified with dimples. clear aligners.
There are limitations to this method of mod- Another discrepancy in the first order can also
ifying the aligner to generate additional rota- manifest in the form of a tooth that is labially or
tional forces. It seems to be more effective for lingually tipped from its predicted position and
anterior teeth as opposed to posterior teeth, failing to track with the aligner. In this case, the
most likely because of the latter’s greater tooth clinician should verify that the tooth’s contact
mass. If the tooth is significantly off-track, areas are not overly tight and perform light strip-
such as greater than 15° from the predicted ping as necessary for the tooth to move freely.
position, then it is unlikely the aligner can Subsequently, the aligner can be modified with
properly encapsulate the tooth to generate an both a dimple plier and a spacer plier (Fig. 11.6).
appreciable rotational force. In such cases, it is If an additional labializing force to the tooth is
Fig. 11.4 (a) The placement of mesiolingual (left) and aligner may result in more difficulty for the patient in seat-
distolabial (right) dimples within the aligner can enhance ing the aligner. The patient is recommended to use a
the distolingual rotation of a maxillary lateral incisor. (b) chewie to improve fitting after alterations of aligner
After the placement of dimples, the distortion of the geometry
desired, then a 1 mm dimple should be placed on Optimizing Tooth Movement

the lingual surface of the aligner, while additional
space should be added to the labial surface with In certain cases, the aligner can be modified by
the spacer plier so that the tooth can move labi- other means to enhance orthodontic movements
ally (Fig. 11.7a). For additional labial movement, that are challenging for the appliance either
two 1 mm dimples can be added on the lingual because of the difficulty or the extent of tooth
surface of the aligner material (Fig. 11.7b). For a movement. Hand instruments can be used to
lingualizing force, the placement of the dimple incorporate new attachments or modify previ-
and the enlargement would be reversed. It should ously programmed attachments. We have dis-
be noted that the dimple should be placed along cussed the significance of attachments in
the long axis of the tooth to produce a labializing optimizing tooth movements [5, 6]. During treat-
or lingualizing force that is as bodily as ment, the addition of attachments can serve as a
possible. means to increase retention of the aligners and
There are cases when dimples are mistakenly facilitate the execution of planned tooth move-
placed in an area of the aligner that is not ideal ments within the arch. For example, precision
for the optimal delivery of forces. The clinician cuts on lower molars offer significant benefits for
can remove the dimple and restore the aligner Class II elastics. However, one of the disadvan-
material to its original state with an eraser plier tages of precision cuts as opposed to button cut-
(Fig. 11.8). In this way, the clinician can ensure outs is the possibility of the patient dislodging the
optimal force delivery when intervening during a mandibular aligner during elastic wear. Beveled
course of aligners and when modifying the attachments, including horizontal and vertical
aligner material. attachments, have been shown to increase reten-
Fig. 11.6 The 1 mm dimple plier (left) can create a labi-

alizing or lingualizing force, while the spacer plier (right)
can be concurrently used to create space into which the
displaced tooth can be moved
retained with additional attachments on the man-

dibular molars and allow for both regular elastic
wear and execution of the planned molar
movements.
Discrepancies in the Third Order
It has been discussed that torque is difficult to

achieve with clear aligners (Chap. 8). Studies
have analyzed the efficacy of torque in clear
aligner therapy and shown an improved move-
ment accuracy with altered aligner geometry [5].
Fig. 11.5 (a, b) For patient J. X., the maxillary right
These geometric alterations can be applied dur-
canine remained rotated and infraerupted after the first ing the course of treatment to enhance torquing
course of aligners. A course of partial fixed appliances movements in upright or proclined anterior teeth.
with metal buttons was employed to derotate and extrude For a tooth that is overly upright and not torqued
the canine through a course of vertical elastics. The
aligner was cut to allow vertical elastics wear. After
in accordance with the software model, a hori-
4 months, the canine rotation was completely corrected zontal dimple of 3 mm can be placed in the labio-
and the tooth extruded into ideal interdigitation gingival region of the aligner material respective
to the upright tooth with the horizontal dimple
tion significantly, as compared with ellipsoid plier (Fig. 11.10a). The 3 mm horizontal dimple
attachments and when no attachments are used will serve as a power ridge and aid in tipping the
[7]. To address the situation, a 3 mm horizontal crown labially and the root lingually (Fig. 11.10b).
dimple can be placed on either the mandibular Another point of force or pressure point can be
first molar or the mandibular second molar with a placed on the aligner material corresponding to
3 mm horizontal dimple plier (Fig. 11.9). The the lingual surface of the incisor near the incisal
horizontal dimple will serve as the template for edge. The two-point application of forces will
an additional attachment on the mandibular create a couple to more effectively produce lin-
molar. Consequently, the aligner would be better gual root torque.
a b
Fig. 11.7 (a) The enlargement on the labial surface of the lingual surface of the aligner material can supplement the
aligner facilitates the labial movement of a lingually dis- labializing force of the aligner
placed tooth. (b) The placement of two dimples on the
Fig. 11.8 The eraser plier (left) can remove attachments

for the placement of dimples or remove dimples produc-
ing undesired forces
Fig. 11.10 (a) The 3 mm horizontal dimple plier can cre-

ate an indent on either labial or lingual surfaces near cer-
vical areas for lingual root torque or labial root torque,
respectively. (b) A power ridge has been created with a
3 mm horizontal dimple plier for lingual root torque
Conversely, the horizontal dimple can also be

placed in the lingual regions of the aligner mate-
rial respective to maxillary and mandibular inci-
sors for labial root torque. At present, power
ridges for lingual regions of incisors cannot be
programmed with most software, except for that
of uLab. Therefore, in most software, the addi-
tion of power ridges with hand instruments is the
Fig. 11.9 The 3 mm horizontal dimple plier can create only current method of altering aligner geometry
indentations for additional attachments or power ridges
during the course of treatment
to supplement labial root torque.
Inter-arch Discrepancies a
During the course of a series of aligners, inter-

arch discrepancies can arise that either were not
anticipated, such as a midline discrepancy, or
may persist due to inadequate biological response
in the patient as a result of one’s mechanics, such b
as a residual deep bite, open bite, or overjet. In
these cases, the clinician can intervene with hand
instruments and auxiliary measures to either
shorten a refinement course or to aid in detailing
and finishing to avoid an additional refinement
course altogether.
Midline Discrepancies Fig. 11.11 (a, b) A midline discrepancy can occur dur-
ing the course of treatment due to heavy occlusal interfer-
Midline discrepancies may manifest during the ences resulting in functional shifts, Bolton discrepancies,
course of treatment as a result of an inadequate underlying skeletal asymmetries, or undesired tooth
movements. A midline deviation of 1–2 mm can be cor-
biological response within the patient or as an rected by creating precision cuts on opposite canines for
unanticipated effect of tooth movement cross midline elastics wear with 1/4’’, 2.7 oz. or 1.4’’, 4
(Fig. 11.10). Practitioners have shown that cross oz. elastics
midline elastics can be effective in the correction
of dental asymmetries [8]. The cross midline The clinician should also be conscious of the
elastic effect can be simulated in clear aligners by possibility that the aligners may dislodge with
incorporating precision cuts on the aligner mate- the use of cross elastics, especially with heavier
rial respective to the mandibular left canine and elastics, like ¼”, 4 oz. or 3/16”, 4 oz. elastics. A
the maxillary right canine to shift the mandibular solution to dislodging is the creation of button
midline to the right. Conversely, in order to shift cutouts on the respective teeth, bonding metal or
the midline to the left, precision cuts would be clear buttons, and instructing the patient to run
incorporated on the aligner material respective to the cross elastics between the buttons. The clini-
the mandibular right canine and the maxillary left cian should be cautious that the forces produced
canine. A minor midline discrepancy of 1–2 mm by the cross elastics do not cause unwanted rota-
can be remedied in 6–8 weeks in a compliant tions in the canines.
patient (Fig. 11.11). These precision cuts can be
programmed into the course of aligners during
the initial Clincheck; however, they may have Deep Bites
been initially omitted, often because of limita-
tions in the clear aligner software. If a midline Previously, we have discussed the difficulties in
discrepancy manifests toward the end of a course clear aligner therapy for the treatment of deep
of aligners, the clinician can modify the aligner overbites (Chap. 6) [9]. Though the G5 protocol
material with either a hole punch plier has allowed for increased effectiveness, it is still
(Fig. 11.12a) or a precision cut plier (Fig. 11.12b) common for deep bites to persist toward the end
to create the appropriate precision cuts and allow of the first or even second course of aligners. In
the patient to wear cross midline elastics these cases, the clinician can modify the aligner
(Fig. 11.13). In this way, the clinician can coordi- material during the course of treatment to
nate the maxillary and mandibular midlines in the enhance bite opening mechanics. Often, the pro-
final stages of a course of aligners. grammed placement of the bite ramps will be
a b
Fig. 11.12 (a) A hole punch plier can be useful in creating precision cuts for intermaxillary elastics or vertical elastics
to opposing teeth. (b) The precision cut plier can create cuts for elastics wear
Fig. 11.13 The precision cut plier can be used for the addition of precision cuts for cross midline elastics
nonideal due to limitations in the software. For the lingual surfaces of the maxillary canines for
instance, in Class II patients with significant a greater disoccluding effect.
overjet, the bite ramps on the material respec-
tive to the lingual surfaces of the maxillary cen-
tral and lateral incisors may not occlude with Anterior Open Bites
the opposing mandibular incisors. As a result,
the bite ramps may not properly disocclude the Clear aligners have been historically effective in
posterior teeth and will therefore remain non- the treatment of anterior open bites even when
functional. The clinician can enlarge the bite compared with fixed appliances (Chap. 7) [10].
ramps with the bite ramp plier so that they prop- However, situations may arise during a course of
erly contact the opposing mandibular teeth aligners in which the open bite has not been com-
(Fig. 11.14). Alternatively, the clinician can add pletely closed or more rarely, manifests for the
bite ramps to the aligner material respective to first time during treatment. In these cases, the
Posterior Open Bites
One of the most common criticisms leveled at

clear aligner therapy is its clinical performance in
finishing with solid posterior contacts and proper
posterior interdigitation. In 2016, Invisalign
introduced a number of enhancements in its G7
generation to improve finishing, including the
minimization of posterior open bites. Specifically,
heavy anterior contacts triggered the Invisalign
software, which automatically created a 0.5 mm
more than normal overjet to remove anterior
interferences. This enhancement has lessened the
Fig. 11.14 The bite ramp plier allows the enlargement of
bite ramps for contact with the mandibular incisors and frequency and severity of posterior open bites in
proper disocclusion of the buccal segments to enhance the finishing stages of clear aligner therapy. The
bite opening in deep bite cases clinician should ensure that no heavy anterior
interferences remain during Clincheck develop-
ment as a means of preventing the development
of posterior open bites later in treatment (we fur-
ther discuss posterior open bite prevention in
Chap. 12). However, despite these precautions
and the incorporation of G7 innovations, poste-
rior open bites still commonly manifest them-
selves. These discrepancies vary widely in
severity and etiology and must be addressed with
the appropriate strategy.
Minor posterior open bites which present with
fewer than 1 mm interocclusal distance are most
often due to the thickness of the aligner itself.
These minor discrepancies can be resolved by
Fig. 11.15 In open bite cases, the addition of bite ramps switching the patient to nightly wear with Essix
onto maxillary molars can simulate a bite block effect and
promote molar intrusion
retainers to allow for occlusal settling. For a
greater settling effect, the clinician can consider
patient will most likely require an additional wraparound Hawley retainers for the maxilla and
course of refinement. However, the clinician can an Essix in the mandible (Fig. 11.16c−e).
promote open bite closure by modifying aligner Posterior open bites of moderate severity
material to reduce total treatment time. In partic- (1–2 mm interocclusal distance) are often attrib-
ular, bite ramps can be placed with a bite ramp uted to residual heavy anterior interferences. One
plier on the occlusal surfaces of both maxillary or of the first solutions the clinician should consider
both mandibular molars to simulate the intrusive is the sectioning of the maxillary aligner at the
effects of a posterior bite block (Fig. 11.15). In distal of the maxillary canines. The patient can
this way, the clinician can enhance intrusive then wear the sectioned canine-to-canine aligner
forces on maxillary or mandibular molars to pro- for 4–6 weeks for extrusion of the posterior seg-
mote open bite closure. ments. If the posterior open bite persists, the cli-
a b
c d
Fig. 11.16 (a, b) For this patient who completed a single illary posterior teeth extruded into ideal interdigitation.
refinement course but still showed a lateral open bite, the (c−e) During retention, a wraparound maxillary Hawley
upper aligner was sectioned distal to both maxillary retainer can allow for occlusal settling and proper inter-
canines for settling of the posterior teeth. After 2 months digitation if a mild posterior open bite persists following
of patient wear with the sectioned upper aligner, the max- clear aligner treatment
Finishing for Treatment Efficacy 173
Fig. 11.17 For local posterior open bites caused by the infraeruption of 3–4 teeth, metal buttons can be bonded on the
problematic teeth for a short course of vertical elastics to achieve lateral open bite closure
nician can either bond buttons and run vertical opening in both the anterior and posterior seg-
elastics between the infraerupted teeth or develop ments. The most prudent resolution would be
an additional refinement course to extrude the for the clinician to rescan the arches and to
posterior segments. develop a refinement course of aligners for cov-
Severe posterior open bites (greater than erage and intrusion of the erupting second
2 mm) often result from residual heavy anterior molars for open bite closure.
interferences, overly tipped posterior teeth, or a
combination of both. In extraction therapy, unde-
sired tipping of premolars and molars often Finishing for Treatment Efficacy
occurs resulting in severe lateral open bites. If the
posterior open bite is local and caused by 3–4 A number of intraocclusal and interocclusal dis-
posterior teeth, the clinician might consider verti- crepancies can arise during the finishing stages
cal elastics between the improperly tipped teeth largely due to the limitations of the clear aligner
to close the open bite (Fig. 11.17). We have suc- appliance. A variety of methods including hand
cessfully demonstrated this method of posterior instruments and other adjunctive means can be
open bite closure in complex cases involving employed for both finishing and correcting more
extraction therapy [11]. In other cases, when the global discrepancies during the course of treat-
posterior open bite is severe or widely d istributed, ment in order to reduce treatment time and
the most effective means of closure is most likely increase effectiveness of therapy. The clinicians
an additional course of refinement. should exercise clinical judgment when deciding
In certain cases, a patient may develop a when to intervene with adjunctive measures as
combination of an anterior open bite and lateral opposed to immediately continuing toward an
open bites, often due to a heavy posterior inter- additional course of refinement. There are situa-
ference. This scenario is commonly seen in ado- tions when discrepancies are too significant, such
lescent patients whose second maxillary or as significant rotations and residual deep over-
mandibular molars were not completely covered bites, for hand instruments and adjunctive strate-
with aligner material due to complete lack of gies and require more extensive intervention.
eruption or partial eruption. During treatment, Nevertheless, the appropriate use of auxiliaries
the eruption of the second molars leads to a pos- can alleviate minor discrepancies as well as
terior premature contact and significant bite enhance aligner biomechanics.
References 6. Djeu G, Shelton C, Maganzini A. Outcome assess-

ment of Invisalign and traditional orthodontic treat-
ment compared with ABO objective grading system.
1. Rossini, et al. Efficacy of clear aligners in controlling
Am J Ortho Dentofac Orthop. 2005;128:292–8.
orthodontic tooth movement: a systematic review.
7. Dasy H, Dasy A, Asatrian G, Rózsa N, Lee H-F,
Angle Orthod. 2015;85(5):881–9.
Kwak JH. Effects of variable attachment shapes and
2. Izhar A, Singh G, Goyal V, Singh R, Gupta N, Pahuja
aligner material on aligner retention. Angle Orthod.
P. Comparative assessment of clinical and predicted
2015;85(6):934–40.
treatment outcomes of clear aligner treatment: an
8. Ikeda Y, Kokai S, Ono T. A patient with mandibu-
in vivo study. Turk J Orthod. 2019;32(4):229–35.
lar deviation and 3 mandibular incisors treated
3. Kravitz ND, Kusnoto B, Agran B, Viana G. How
with asymmetrically bent improved superelastic
well does Invisalign work? A prospective clini-
NiTi alloy wires. Am J Ortho Dentofac Orthop.
cal study evaluating the efficacy of tooth movement
2017;153(1):131–43.
with Invisalign. Am J Orthod Dentofac Orthop.
9. Papadimitriou A, Mousoulea S, Gkantidis N, Kloukos
2009;35:27–35.
4. Kravitz ND, Kusnoto B, Agran B, Viana G. Influence
2018;19(1):37.
accuracy of canine rotation with Invisalign: a prospec-
10. Garnett BS, Mahood K, Nguygen M, Al-Khateeb A,
tive clinical study. Angle Orthod. 2008;78(4):682–7.
Liu S, Boyd R, Oh H. Cephalometric comparison of
adult anterior open bite treatment using clear aligners
and fixed appliances. Angle Orthod. 2019;89(1):3–9.
technique—regarding incisor torque, premolar dero-
11. Cisneros G, Huang AT, Huang D. Situational extrac-
tion therapy with clear aligner therapy in complex
2014;14:68.
malocclusions. Orthod Pract US. 2019;10(2):14–20.
When and How to Overcorrect?
12
Contents
The Various Roles of Overcorrection 175
Indications and Methods for Overcorrection 176
A Conservative Approach for Overcorrection 184
References 186
The Various Roles of Overcorrection The method of overcorrection also plays a

vital role in the treatment planning of extensive
One of the most controversial aspects of clear jaw movements, such as mandibular autorotation
aligner therapy is the role of overcorrection for open bite closure, the simulation of jaw
during treatment planning and the design of vir- growth, and mandibular forward repositioning
tual setups. Frequently, overcorrection serves with the MA appliance (Chap. 3).
as a measure to counteract the inaccuracy of A less commonly discussed application of
unpredictable tooth movements. Various stud- overcorrection is for residual space closure, espe-
ies have recommended overcorrection to cially following extractions or IPR. The planning
achieve planned movements considered diffi- for precise space closure can pose a dilemma, as
cult for clear aligners, including anterior tooth underprescribing virtual C-chains can result in
extrusion and intrusion, posterior tooth expan- unclosed spaces, while overprescribing can cause
sion, and canine and premolar derotation [1, 2]. adverse effects, such as an excessive overjet.
Overcorrection should also be considered for These considerations are especially important for
tooth movements involved in the treatment of extraction cases, as extraction space closure has
Class II malocclusions, especially those involv- been shown to be highly unpredictable [4].
ing posterior teeth distalization. Studies have One of the most controversial uses of overcor-
shown effective maxillary molar distalization rection has been for the proper finishing of the
within the range of 2–3 mm, but overcorrection occlusion. Specifically, the correction of deep
should be considered for movements at the bites and posterior open bite closure can benefit
upper end or beyond this range to achieve from overcorrection [5]. However, excessive
desired outcomes [3]. overcorrection can introduce another element of
https://doi.org/10.1007/978-3-030-92810-0_12
176 12 When and How to Overcorrect?
unpredictability to treatment and result in adverse expression of overbite reduction programmed

effects, especially in the vertical dimension. in the Clincheck software [6]. This result is
There remains uncertainty regarding the most likely associated with the low accuracy of inci-
judicious methods of overcorrection for achiev- sor intrusion, even following technological
ing a proper final occlusion. advancements, such as the G5 protocol [7].
Overcorrection has emerged as a viable Various studies have recommended the incor-
approach for enhancing the predictability of both poration of auxiliary appliances, such as TADs,
dental and jaw movements, as well as an essential or the modification of the software projection,
tool for achieving a harmonious final occlusion. in the form of overcorrection, to improve over-
However, although overcorrection has been fre- bite control with clear aligners [5]. The clini-
quently referenced in the literature, its exact use cian should seriously consider overcorrection
has not been thoroughly discussed. To address for severe overbites, as the deeper the initial
the ambiguities surrounding overcorrection, this overbite, the more difficult it will be to achieve
chapter details its indications and methods for overbite reduction [6].
clinical applications ranging from treatment Because of these limitations in the predictabil-
planning challenging movements to occlusal ity of overbite control with clear aligners, it is
finishing. recommended in the treatment of deep bite cases
that the clinician overcorrect the amount of intru-
sion of maxillary incisors and mandibular inci-
Indications and Methods sors by 1–1.5 mm for each arch so that the
for Overcorrection programmed final occlusion shows 0 mm over-
bite. This is in accordance with the findings of
Unpredictable Tooth Movements previous studies, which have shown significant
overbite reduction through the G5 protocol, ade-
Unpredictable Tooth Movements: quate leveling of curves of Spee, and overcorrect-
Anterior Teeth Intrusion ing overbites to 0 mm [5]. A similar overcorrection
One of the most common indications for over- approach can be employed in programming max-
correction is the intrusion of maxillary and illary incisor intrusion supplemented with TADs:
mandibular anterior teeth for the correction of 2 mm of additional intrusion can be incorporated
deep overbites (Table 12.1). Recent studies for the maxillary incisors (Fig. 12.1).
have shown low predictability in the clinical
Unpredictable Tooth Movements:
Table 12.1 Indications for overcorrection among chal- Anterior Teeth Extrusion
lenging tooth movements Recent studies suggest the accuracy of incisor
Indications for Guidelines for extrusion has significantly improved from ear-
overcorrection overcorrection lier generations of clear aligners [7]. These
Intrusion Overcorrect 1–1.5 mm/arch improvements are likely due to multiple factors,
Extrusion 0.5–1 mm for extensive including the introduction of SmartTrack mate-
extrusive movements
rial in 2013, the use of optimized extrusion
Derotation Overcorrect canine and
premolar rotations by 5° attachments, and variations in study designs.
Expansion Overcorrection of an Studies have also observed efficacy in clear
additional 1 mm of aligners for open bite closure through incisor
expansion extrusion, molar intrusion, and autorotation of
Root uprighting Overcorrection of root tip by the mandible. However, despite these improve-
approximately 5°
Relative extrusion/ 1–2 mm intrusion/1–2 mm
ments, extrusion accuracy remains low, relative
relative intrusion extrusion to other movements such as rotation or crown
Lingually displaced Overcorrect labial root tip [1]. As discussed in Chap. 7, the predictabil-
maxillary lateral incisors torque by approximately 5° ity of anterior teeth extrusion, especially in
Fig. 12.1 For maxillary incisor intrusion assisted with TADs, an additional 2 mm of intrusion can be programmed to
simulate the supplementary intrusive force
treatments of open bite closure where a signifi- Unpredictable Tooth Movements:

cant amount of incisor extrusion is required, can Derotation
be enhanced by combining pure extrusion with The rotation of canines and premolars has been
retraction for relative extrusion and through shown to be imprecise when compared to planned
overcorrection of the movement. movements on virtual setups, even in aligner sys-
Specifically, the clinician should consider an tems alternative to Invisalign [8]. Various studies
overcorrection of approximately 0.5–1 mm for have shown mandibular canine rotation is one of
extensive extrusive movements, such as those the least accurate movements and its accuracy
>3.5 mm, which Align Technology classifies as falls significantly in rotations exceeding 15° [9].
an advanced amount of extrusion (<2.5 mm is Because of the low accuracy in both canine and
considered mild extrusion, while 2.5–3.5 mm is premolar rotation, since early generations of
classified as moderate extrusion). Recent studies clear aligners, clinicians have recommended
have similarly advocated for overcorrection by measures such as IPR adjacent to the tooth to be
0.5 ± 0.1 mm, based on a difference between pre- rotated, slowing down the velocity of rotation per
dicted and achieved values for extrusion, whether aligner, and overcorrection [10]. Recent studies
with optimized or conventional attachments [1]. have suggested overcorrection for canines and
For open bite cases, the amount of extrusion for premolars, even with the incorporation of opti-
the maxillary and mandibular incisors can be mized attachments [1].
overcorrected by 1 mm per arch to enhance the Various strategies have been proposed for
predictability of open bite closure. overcorrection in the derotation of canines and
premolars, including overcorrecting by an Unpredictable Tooth Movements:

additional 10% of the programmed amount of Complex Movements
rotation [11]. It is recommended that the clinician We have discussed the significance of overcorrec-
overcorrect the rotations of canines and premo- tion for complex movements, such as molar
lars by 5°, especially for rotations greater than uprighting and root torquing. Studies on the per-
15°. This method was also suggested by a recent formance of clear aligners in extraction cases have
study which found the mean difference between suggested overcorrecting the distal tip by 6° on
predicted and achieved amounts of rotation rang- first molars adjacent to extraction spaces to main-
ing from 4.01° to 6.01° (with the use of optimized tain root angulation and to achieve more bodily
attachments for the former and conventional tooth movement [4]. For significant space closure
attachments for the latter) [1]. For the treatment in both extraction and non-extraction cases, the
of extremely rotated teeth, such as those requir- amount of root tip may have to be overcorrected in
ing greater than 45° rotation, the clinician should the teeth adjacent to the edentulous space for
consider adjunctive fixed appliances [12]. bodily movement and proper root parallelism.
For extensive space closure, the virtual gable
Unpredictable Tooth Movements: bend should be requested as a form of overcor-
Expansion rection to help ensure root parallelism. Similarly,
Studies that have investigated the predictability for significant root tipping for uprighting teeth,
of expansion with clear aligners have observed such as in the preparation for implant restora-
discrepancies between planned and achieved tions, the clinician should consider overcorrect-
movements in both arches. One of the most inac- ing the amount of root tip by approximately 5° to
curate sites for expansion has been bodily expan- achieve desired movements.
sion for the maxillary molars, while the canine
region has been demonstrated to show greater ontrolling the Vertical Position
C
accuracy for expansion [13]. Therefore, the clini- of Incisors
cian should consider overcorrection for signifi- Studies on efficacy of clear aligners in first pre-
cant expansion of the posterior region of the molar extractions have shown greater loss of
maxilla, especially for the first and second maxil- torque than planned in incisors during retraction,
lary molars. resulting in relative extrusion of incisors and
Studies have observed in the treatments of undesired deepening of overbite [4]. A loss of
patients with transverse malocclusions, a dis- torque also occurs even with the application of
crepancy between predicted and achieved values attachments or power ridges [14]. To control the
of expansion of 0.69 mm at the first molar, vertical position and angulation of incisors dur-
0.81 mm at the second premolar, and 0.77 mm at ing significant retraction, it has been recom-
the first premolar [2]. To correct for this inaccu- mended to overcorrect lingual root torque for the
racy, in cases that require significant maxillary maxillary incisors. Additionally, the clinician
expansion, such as patients with teeth in poste- should consider overcorrection of the amount of
rior crossbite, an overcorrection of an additional intrusion prescribed for the maxillary incisors to
1 mm of expansion can be incorporated for the counteract the relative extrusion associated with
posterior segment with the transverse discrep- loss of torque. Similarly, in non-extraction cases
ancy to achieve desired outcomes. In addition to with significant retraction of the maxillary or
overcorrecting the amount of expansion, the cli- mandibular incisors, overcorrection should be
nician should also consider presetting buccal considered for both torque and intrusion of the
root torque for posterior expansion due to the incisors to be retracted.
low accuracy of bodily expansion with clear Conversely, for incisors planned for move-
aligners (although this efficacy may have ments associated with relative intrusion, the cli-
improved since the incorporation of Invisalign’s nician should consider overcorrection for the
G8 modifications). amount of extrusion to maintain the desired
v ertical position of the incisors. For example, incisors, will require difficult movements includ-
for cases involving expansion or significant ing extrusion and derotation. Overcorrection
labialization of the incisors, such as the pro- should be incorporated as high maxillary canines
traction of maxillary incisors for the treatment will require extensive extrusion, which as dis-
of Class III malocclusions, extrusive move- cussed, remains a weakness for clear aligner ther-
ments should be incorporated to counteract the apy. The clinician should consider an
relative intrusion associated with labialization overcorrection of an additional 1 mm extrusion
(Fig. 12.2). for high maxillary canines to counteract the
For incisors planned for significant retraction, unpredictability of the appliance in extrusive
the clinician can incorporate power ridges in movements, as observed in previous studies.
addition to an overcorrection of 1–2 mm intru- Often, even with overcorrection, high maxillary
sion to counteract loss of torque and relative canines will need auxiliary measures, such as
extrusion. Likewise, for incisors that will be labi- vertical elastics for a supplementary extrusive
alized, an overcorrection of 1–2 mm extrusion force, for ideal finishing.
can be employed to compensate for the effects of Lingually displaced maxillary lateral incisors
relative intrusion. will typically require significant derotation,
exceeding 15°, and therefore warrant overcor-
Irregularly Positioned Teeth rection of approximately 5°. The roots of these
Severely displaced teeth, such as high maxillary lateral incisors also tend to be lingually inclined
canines or lingually displaced maxillary lateral and often require labial root torque to achieve
Fig. 12.2 For incisors to be labialized by significant amounts, the clinician should consider overcorrecting extrusion
by 1–2 mm to compensate for relative intrusion
proper labiolingual inclination. As clear align- J aw Growth in Growing Patients

ers tend to perform inaccurately with torque As discussed in Chap. 3, the MA appliance
control, it would be prudent for the clinician to advances the mandible, typically in a stepwise
overcorrect for labial root torque by approxi- fashion, for the treatment of Class II malocclu-
mately 5° [14]. sions. The position of the mandible should be
overcorrected to an edge-to-edge incisor rela-
tionship with slightly overcorrected Class I
Unpredictable Jaw Movements canine and molar relationships, bilaterally
(Fig. 12.3). This method accounts for relapse
Mandibular Autorotation and simulates the protocol successfully employed
We have discussed the significance of posterior in treatments with the Herbst appliance, which
intrusion for mandibular autorotation and suc- frequently advance the mandible to edge-to-edge
cessful open bite closure (Chap. 7). Though the incisor relationships [16]. For cases requiring
intrusion of mandibular second molars has significant advancement, such as an overjet
been shown to be more accurate than their >6 mm, the clinician should consider overcor-
extrusion, intrusion remains unpredictable at rection of the mandible 1–2 mm forward of the
about 50% accuracy [7]. A study on the effi- edge-to-edge position so that the canines and
cacy of open bite closure with clear aligners molars will lie in Class III relationships,
without auxiliaries demonstrated that even bilaterally.
with intrusion programmed into the trays, a Conversely, the virtual setups for the orthope-
mean of only about 0.6 mm of intrusion of dic treatment of a growing Class III patient, such
maxillary molars and 0.4 mm of intrusion of as with the RPFM, should be overcorrected so
mandibular molars were achieved during treat- that the final occlusion shows 1–2 mm of positive
ment [15]. These data suggest in severe open anterior overjet (Fig. 12.4). This setup will
bite cases, measures such as overcorrection account for the supplementary orthopedic forces
and skeletal anchorage should be employed to applied to the maxilla and maxillary teeth.
enhance molar intrusion. Studies have also frequently recommended over-
For severe open bite cases, the clinician should correction in skeletal Class III correction for
consider overcorrection by an additional 1 mm of long-term stability [17].
intrusion for both the maxillary and mandibular
molars (Table 12.2). This amount of overcorrec-
tion should also be incorporated for TAD- O cclusal Finishing
supported molar intrusion to realistically simulate
the effects of supplementary intrusive force from O verjet
the TADs. As discussed in Chap. 11, one of the most fre-
quent challenges of clear aligner therapy is the
development of a posterior open bite during treat-
Table 12.2 Indications for overcorrection among jaw
movements
ment. Though some practitioners have claimed
that posterior open bites can be attributed to
Indications for
overcorrection Guidelines for overcorrection intrusion of the molars from a bite block effect of
Molar intrusion for Additional 1 mm for the clear aligners, recent studies have shown pos-
mandibular autorotation maxillary and (or) terior intrusion does not occur with clear aligners
mandibular molars when not prescribed [18]. Therefore, it is likely
MA appliance Correction to 1–2 mm that most posterior open bites are due to heavy
beyond edge-to-edge for
severe discrepancies anterior interferences. The primary method for
Orthopedic treatment of Overcorrect positive overjet avoiding heavy anterior interferences is to con-
growing Class III by 1–2 mm firm light contacts in the maxillary and mandibu-
patient lar anterior teeth within the final occlusion of the
Fig. 12.3 For cases with severe overjets treated with the relationships and 1 mm beyond the edge-to-edge position.
MA appliance, the clinician shoulder consider overcor- This approach can more predictably achieve ideal sagittal
recting the final occlusion to Class III molar and canine relationships and overjet reduction
virtual setup. The clinician should also set a teeth remains inaccurate relative to movements
0.5 mm more than normal overjet of 1–2 mm to like crown tipping and intrusion and the amount
reduce the likelihood of heavy anterior interfer- of extrusion necessary is typically extensive,
ences (the G7 modifications may automatically exceeding 0.5 mm, it is recommended that the
trigger this default overcorrection in the Invisalign clinician overcorrect extrusion of posterior teeth
system, which the clinician should consider within 0.5 mm to achieve posterior open bite clo-
accepting during the development of the virtual sure (Fig. 12.5).
setup).
Overbite Residual Space Closure

In programming the final overbite in the virtual
setup for the treatment of deep bite cases, the cli- Virtual C-Chain
nician should consider overcorrection of The judicious use of virtual C-chains, the equiva-
0.5–1 mm for both the maxillary and mandibular lent of the power chain in fixed appliances, is
incisors to approximately 0 mm overbite, as sug- essential for proper closure of residual spaces in
gested by studies on efficacy of incisor intrusion both extraction and non-extraction cases and the
with clear aligners [19]. It is important to note avoidance of adverse effects, such as excessive
that overcorrection to beyond 0 mm overbite is overjet or undesired tipping. In premolar extrac-
not recommended, as this method may result in tion cases, the canine to canine C-chain should
an anterior open bite if the patient is not closely not be employed or employed sparingly, as its
monitored. overuse will result in the reopening of extraction
spaces distal to the canines. Instead, in these
Posterior Interdigitation cases, a first molar to first molar or second molar
Often, the reduction or equilibration of heavy to second molar C-chain should be requested for
anterior interferences may not be adequate for complete closure of all residual spaces. A canine
the closure of a posterior open bite. Instead, the to canine C-chain is suitable for cases with
posterior teeth may have to be extruded for proper extractions of exclusively anterior teeth, such as a
interdigitation. Because extrusion of posterior single mandibular incisor.
Fig. 12.4 Orthopedic treatment of growing patients with for the supplementary forces supplied by orthopedic max-
Class III patients should employ a bite jump with overcor- illary protraction
rected amount of positive overjet. This method accounts
For non-extraction cases, a C-chain from mandibular arch can result in over-retraction of
canine to canine can be employed for cases the mandibular incisors and increased overjet.
involving anterior spacing or exclusively anterior Therefore, C-chains should be used in a conser-
IPR. Typically, a single C-chain should be ade- vative fashion to prevent compromising proper
quate if the IPR prescribed were not excessive for occlusal outcomes. In most cases, a single
the initial severity of crowding. However, for C-chain for either arch should be adequate; if
non-extraction cases with generalized spacing or greater than one C-chain for a single arch is nec-
requiring posterior IPR, a first molar to first molar essary, then the clinician should program passive
or second molar to second molar C-chain, rather aligners for the opposing arch to avoid excessive
than a canine to canine chain, should be requested movements.
for complete closure of all residual spaces.
The overuse of C-chains can result in adverse
effects, such as the skewing of the arches, the tip- Distalization
ping of posterior teeth due to significant mesial
movement without adequate root control, and Studies have shown that clear aligners in the
posterior open bite due to the tipping of posterior absence of auxiliaries can distalize molars by
teeth (Fig. 12.6). Excessive use of C-chains in the approximately 2 mm without significant tipping
Fig. 12.5 It is recommended that the clinician overcor- amount of extrusion for the right maxillary first molar has
rect the extrusion of posterior teeth within 0.5 mm when been overcorrected by about 0.3 mm
seeking to achieve ideal interdigitation. In this case, the
or extrusive movements [3]. Distal movements of

molars significantly greater than 2 mm are likely
to be more unpredictable than more minor move-
ments. As a result, for extensive distalization of
molars, such as movements exceeding 2 mm, the
clinician should consider auxiliaries, such as a
bonded molar distalizer, and overcorrect the
amount of distalization by 0.5–1 mm to account
for the supplementary distalizing force (Fig. 12.7).
Fig. 12.6 The excessive application of VCCs can result

in tipping of posterior teeth. In this patient, excessive Conservative Approach
A
VCCs for the maxillary arch resulted in tipping of the for Overcorrection
right maxillary first molar. This tipping was treated by
bonding a metal button on the mesiobuccal cusp of the
Despite an abundance of conflicting perspectives
right maxillary first molar and short round of vertical elas-
tics to the opposing arch on the proper use of overcorrection, there exist
clear indications for its application in challenging
Fig. 12.7 Maxillary distalization supplemented with dis- aligners and a Carriere distalizer, the amount of distaliza-
talizing appliances should be represented by overcorrect- tion programmed for the maxillary posterior teeth was
ing the amounts of distalization for the maxillary posterior overcorrected by about 0.5 mm
teeth. For patient A.C., who received treatment with clear
A Conservative Approach for Overcorrection 185
Fig. 12.8 Ideal overjet should not be deliberately com- a nonideal excessive overjet. Instead, the clinician should
promised for the sake of preventing heavy anterior con- consider alternative measures, such as adjusting maxillary
tacts. Above, the clinician has deliberately increased and mandibular incisor inclinations or incorporating
overjet and added excessively heavy posterior contacts to intrusion to these incisors. The clinician can also accept
minimize anterior contacts. However, this maneuver Invisalign’s G7 default adjustment for minimizing ante-
results in an end-on Class II canine relationship, as well as rior interferences
movements, modeling jaw movements, and Instead, the clinician should find alternative ther-
occlusal finishing. The method has been shown to apeutic means to maintain an acceptable overjet
be viable for improving the predictability of both while minimizing heavy anterior interferences,
teeth and jaw movements. such as adjusting the maxillary and mandibular
Nevertheless, overcorrection should be incisor inclinations or intruding the maxillary or
applied in a conservative, targeted manner, as its mandibular incisors.
overuse can adversely affect occlusal outcomes. The rapidly evolving nature of clear aligner
Notably, the overuse of virtual C-chains can therapy suggests that improvements will occur
result in excessive overjet, molar tipping, poste- in the accuracy of tooth movement. For exam-
rior open bites, and crowding. Similarly, overcor- ple, studies have shown a significant increase in
rection should not be employed in a manner that the accuracy of incisor extrusion between gen-
compromises another aspect of the occlusion. For erations of Invisalign. Therefore, the methods of
example, the overjet should not be significantly overcorrection will also have to evolve to remain
increased for the prevention of heavy anterior abreast of these improvements for the
interferences and posterior open bites (Fig. 12.8). appliance.
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gpso.org/events/2003_outline.pdf. Accessed 12 Sep
2021.
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Hernández A, Bellot-Arcís C. Arch expansion with
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the Invisalign system: efficacy and predictability.
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PLoS One. 2020;15(12):e0242979.
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G, Deregibus A. Maxillary molar distalization with
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aligners in adult patients: a multicenter retrospec-
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Alt-RAMEC and facial mask protocol in Class III
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with Invisalign. Am J Orthod Dentofac Orthop.
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changes in vertical dimension and molar position in
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treatment using Invisalign. The Greater Philadelphia
Index
A Class II malocclusion, 24, 53–56, 58, 59, 63, 64, 84, 85,
Anterior open bite 90, 108, 148, 152
bite jump, 120, 148 Clincheck Pro
efficacy, 103, 141 5.0, 2
factors, 102–106, 122
mandibular autorotation, 118
molar intrusion, 118, 120 D
orthodontic treatment, 125 Deciduous teeth, 35
strategies, 113–114 retention, 35, 47, 48, 63
TAD-assisted molar intrusion, 120–122 Derotation, 3, 26, 44, 68, 69, 71, 90
Attachment
design, 2–5, 11, 14, 16, 19, 20, 25, 62, 68, 70, 77–79
optimized, 4, 5, 8, 11, 14, 16, 20, 23–26, 34, 35, 50, E
68–70, 77, 79, 84, 101, 102, 114, 135, 137, 141 Expansion, phase I treatment, 23, 40
Extraction
combination treatment, 144–146
B G6, 135, 146
Bite jump gable bend, 136
controversial uses, 154–157 limitations, 135
functional shifts, 152, 160 predictability, 136
indications, 147–152 tipping, 136–144
open bite closure, 120, 148, 151–152, 155, 160 torque, 141
orthognathic surgery, 20, 152, 157 Extrusion, 1, 3–5, 11, 25, 35, 67, 68, 71, 101, 102, 106,
principles, 148, 152–154 108, 114–116, 118, 119, 121, 122, 124, 126,
timing, 103, 147, 152–154 151, 160
Bite opening accuracy, 67, 68, 114
accuracy, 112
bite ramps, 13, 19, 102–103
extraction, 122, 136, 141 F
G8 modifications, 103, 112 Finishing, 21, 28, 68, 70, 79, 97, 118, 145, 158, 160
leveling curve of spee, 102, 108, 109, 112 First molars, 24, 27, 40, 62, 79, 84, 108, 135, 137, 141
molar extrusion, 101, 108–112 tipping, 2
relative intrusion, 104, 105 Functional appliance
short clinical crowns, 4, 104–106 FR2, 55, 62
Herbst, 54, 55, 59, 62
Twin Block, 59, 62, 64
C
Cephalometric analysis, integration, 10, 17, 19, 142
Class II correction G
retrognathic mandible, 56, 58, 64 G4, 68–69, 84, 114, 115
Class II elastics, 11, 84, 85, 95, 104, 132, 152 G5, 101–104, 108, 112
https://doi.org/10.1007/978-3-030-92810-0
188 Index
G6, 8, 135, 137, 155 solutions, 63

G7, 68–69 vertical elastics, 62
G8, 69, 70, 101–103, 112, 141 Mandibular autorotation, 14, 115, 118, 124, 147,
155, 160
Maxillary lateral incisors
H aligner geometry, 69–70
Hard tissue, 2, 9, 16 combination treatment, 70
modeling, 9, 13, 15, 18–20 G4 attachments, 68–69
G7 attachments, 68–69
missing, 74–76
I overcorrection, 70–71
In-house aligner (IHA), 14, 18–21 restorative treatment, 73–74
Interceptive treatment tooth size discrepancy, 74
attachments, 23 torque control, 71–73
efficacy, 23 Maxillary molar
features distalization, 20, 90
applications, 27 tipping, 137
duration, 27
eruption compensation, 25
limitations O
clinical preferences, 36 Optimized attachments
expansion, 34 efficacy, 114
retention, 40 extrusion, 102, 103, 114
short clinical crowns, 34 maxillary lateral incisors, 69
solutions root control, 20, 77, 79, 84
expansion limits, 48 rotation, 4, 25
retention, 47 Overcorrection extrusion, 71
software calibration, 48
Interproximal reduction
asymmetries, 95 P
class II malocclusions, 90–94 Phase I
class III malocclusions, 90–94 cervical headgear, 43, 44, 148
decrowding, 90 RPFM, 28, 34, 35, 40
incisor uprighting, 95 treatment, 26, 27, 49
indications, 90–96 Power ridge
long-term consequences, 99 dental decompensation, 126
retention, 96 distalization, 132
round tripping, 97 efficacy, 5, 8, 126, 132–134
technique, 96–97 incisor retraction, 85, 126
timing, 97–99 intermaxillary forces, 132
tooth size discrepancy, 94–95 limitations, 6, 126
Invisalign software posterior protraction, 126
attachment design, 2, 5
diagnosis, 10
extraction therapy, 8 R
soft tissue modeling, 9 Root uprighting
torque application, 5, 6 attachment design, 77–79
treatment, 9 auxiliaries, 68, 79, 85, 136
class II treatment, 84–85, 126, 132
extraction, 79–84
M treatment duration, 79, 92
Mandibular advancement virtual gable bend (VGB), 76–77, 79, 85
calibration, 55
case selection, 58
efficacy, 63 S
expansion, 63 Soft tissue, 2, 9, 13, 15, 16, 18, 20, 27, 92, 113, 125
limitations, 54, 58, 63 modeling, 2, 9, 13, 18–20
mandibular incisor inclination, 62 Software
mechanism, 54 ideal, 19–21
precision wings, 59 Invisalign, 2, 4, 5, 8, 9, 11
Index 189
Suresmile, 14, 16 extraction therapy, 108, 126

3M, 11, 12, 14 limitations, 5, 6
U-Lab, 16, 18 power ridge, 5–7, 12, 15, 19, 126–132
Space closure, 1, 8, 21, 76, 78, 106, 108, 126, 135–141, pressure point, 19, 20, 73, 134, 141
146, 147, 155, 156
Suresmile
attachment design, 14 U
bite opening, 15 uLab
soft tissue modeling, 15 attachment design, 16
torque application, 15 bite opening, 18
treatment, 16 soft tissue modeling, 18
software, 16, 18
torque application, 18
T treatment, 18
3D printer, 21 Upper incisors
compatibility, 21 retraction, 76, 93, 125, 137, 141–142
3M software torque control, 71–73, 135
bite opening, 12 Uprighting
soft tissue modeling, 13 molar, 78–80
software, 11, 12, 14 root, 76–85
torque application, 12
treatment, 14
Torque V
aligner geometry, 5, 12, 15, 134 Virtual gable bend
application, 5, 6, 12, 15, 18–20 (VGB), 8, 16, 19, 21, 76–80, 85, 136, 137

Controversies in Clear Aligner Therapy Contemporary Perspectives

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Controversies

ISBN 978-3-030-92809-4 ISBN 978-3-030-92810-0 (eBook)

Authoring an orthodontic textbook to address controversies is refreshing,

illustrating suggested technological modifications, and future clinical appli-

New York, NY Anderson Huang

1 Optimizing Diagnosis and Treatment Planning

Hard and Soft Tissue Modeling �������������������������������������������������� 20

Maxillary Expansion in Conjunction to Mandibular

IPR Technique���������������������������������������������������������������������������������� 96

9 Overcoming Limitations in Extraction Therapy�������������������������� 135

Deep Bites������������������������������������������������������������������������������������ 169

AAO American Association of Orthodontists

 lear Aligner Software: A Brief

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 1

Fig. 1.4 Horizontal beveled attachments were placed on

Fig. 1.5 An Invisalign error message flags the necessary

Fig. 1.3 Invisalign Clincheck permits the clinician to

l­imited by the use of a nonideally configured

crown and root movements by placing lingual

 ingle Tooth Movement: Limitations

 eficiencies in Hard and Soft Tissue

large skeletal discrepancies in the simulated Limitations in Diagnostic Tools

 ptimizing Single Tooth Movement:

to application of the bite ramps is the fact that

Dentsply Sirona Suresmile Software

Like 3M, Dentsply Sirona introduced its

 ptimizing Single Tooth Movement:

 ptimizing Single Tooth Movement:

sions, such as a bite jump function, a mandibular

The uLab software is unique among the various

Fig. 1.21 The uLab

 ptimizing Single Tooth Movement:

Table 1.1 Comparison between major types of clear aligner software

lar to those modeled by imaging software, such References

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 23

For interceptive treatment, Invisalign has

etal Class II discrepancies. The feature sought to

will have to consider retention measures. These Duration of Aligner Wear

Fig. 2.5 (continued)

Fig. 2.5 (continued)

Fig. 2.5 (continued)

Fig. 2.5 (continued)

Fig. 2.5 (continued)

Fig. 2.6 (continued)

patient received a refinement course to distalize standardized cephalometric measurements such

 oftware Calibration for Treatment

Fig. 2.7 (continued)

Fig. 2.7 (continued)

Class III discrepancies, especially of greater

Fig. 2.9 (continued)

Fig. 2.9 (continued)

Fig. 2.10 (continued)

Fig. 2.10 (continued)

Retention to Small Clinical Crowns

The small clinical crowns of the deciduous teeth

gingival problems and recession [22]. Ideally,

The treatment simulation often fails to accurately

The Viability of Interceptive 4. Franchi L, Baccetti T, McNamara JA. Postpubertal

 lass II Functional Correction

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 53

New York, NY Anderson Huang

1 Optimizing Diagnosis and Treatment Planning

Hard and Soft Tissue Modeling �� 20

IPR Technique�� 96

9 Overcoming Limitations in Extraction Therapy�� 135

Deep Bites�� 169

lear Aligner Software: A Brief

limited by the use of a nonideally configured

ingle Tooth Movement: Limitations

eficiencies in Hard and Soft Tissue

large skeletal discrepancies in the simulated Limitations in Diagnostic Tools

ptimizing Single Tooth Movement:

Dentsply Sirona Suresmile Software

ptimizing Single Tooth Movement:

ptimizing Single Tooth Movement:

ptimizing Single Tooth Movement:

will have to consider retention measures. These Duration of Aligner Wear

oftware Calibration for Treatment

Retention to Small Clinical Crowns

The Viability of Interceptive 4. Franchi L, Baccetti T, McNamara JA. Postpubertal

lass II Functional Correction

fficacy in Comparison to Class II

axillary Expansion in Conjunction

ave Clear Aligners Improved

uxiliaries for Enhancement of Tooth

Combination Treatment with Fixed

1. The judicious prescription of virtual gable lements of Successful Uprighting—

Uprighting in Class II Treatment

Tooth Size Discrepancies [10]. IPR can address Bolton discrepancies,

Clincheck setup or through most types of cast Midline Coordination

he Challenge of Deep Bite

Relative Intrusion crowded anterior teeth, the incisors can be over-

Treatment Protocols In the design of the Clincheck, the intrusion of

urrent Strategies for Open Bite

bites treated nonsurgically, while a stability of fficacy of Movements Associated

The Incorporation of Bite Jumps

The most common indication for the use of Posterior Protraction

ingually Displaced Maxillary Lateral

Intermaxillary Forces rather than indiscriminately prescribing power

Controlling Posterior Torque

linical Management of Extraction

Frequency of Aligner Changes

encapsulation. For example, dimples can be Combination Treatment

I mproving the Efficacy of Clear appliances in first-premolar extraction cases. J Clin

is necessary to set up the mandibular forward Open Bite Closure

Extensive Space Closure first molar space can be supplemented with