Original Article

Differences in finished case quality between Invisalign and traditional fixed

appliances:
A randomized controlled trial
Eric Lina; Katie Julienb; Matthew Kesterkec; Peter H. Buschangd

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ABSTRACT
Objectives: To compare the treatment and posttreatment effects of Invisalign aligners that
incorporated SmartForce features and attachments to traditional fixed appliances.
Materials and Methods: This randomized controlled trial included 66 patients, 32 aligners, and 34
fixed-appliance patients. The median ages of the aligner and braces patients were 26.7
(interquartile range [IQR]: 9.8) and 25.9 (IQR: 16.6) years, respectively. Pretreatment occlusion
was assessed using the ABO Discrepancy Index. Posttreatment (T1) and 6-month retention (T2)
occlusions were quantified using the ABO Objective Grading System (OGS) scores.
Results: The braces group finished treatment significantly (P , .001) earlier (0.4 years) than the
aligner group. The median DI scores for the aligner and braces groups were 4.5 and 7.0,
respectively, which was a statistically significant (P ¼ .015), but clinically insignificant, difference.
There were no statistically significant between-group differences for the total OGS scores or any of
the individual component scores at debond (T1) or after 6 months of retention (T2). During the
posttreatment period, alignment and overjet worsened significantly in the aligner group, while
buccolingual inclinations and occlusal relations improved. Over the same period, alignment
worsened in the braces group and buccolingual inclinations improved. There was no statistically
significant between-group difference in posttreatment changes of the total OGS scores.
Conclusions: While patients with simple malocclusions require 4.8 months longer treatment times
with aligners than traditional braces, the treatment and 6-month posttreatment occlusal outcomes
are similar. (Angle Orthod. 2022;92:173–179.)
KEY WORDS: Invisalign; Traditional fixed appliances; RCT; Human; ABO-OGS; Discrepancy
index

INTRODUCTION currently available and patient demographics have

drastically changed over time. Increasing numbers of
Orthodontics has traditionally focused on younger, adults are seeking treatment, and they often present
growing patients.1 However, the appliances that are with greater esthetic demands.2 To meet their de-
mands, an emphasis has been placed on developing
a
Private Practice, Irving, TX, USA. appliances to treat adult patients.
b
Employee Practitioner, Southeast Alaska Regional Heath The advent of clear aligner therapy is one of the
Consortium, AK, USA. most significant developments in orthodontics over the
c
Assistant Professor, Department of Biomedical Sciences,
past 30 years.2 Among the many clear aligners
Texas A&M University College of Dentistry, Dallas, TX, USA.
d
Regents Professor and Director of Orthodontic Research, available, Invisalign (Align Technology, Tempe, AZ) is
Department of Orthodontics, Texas A&M University College of the most widely used.3 Originally meant to treat mild-to-
Dentistry, Dallas, TX, USA. moderate cases, Invisalign has since been used to
Corresponding author: Peter H. Buschang, PhD, Gaylord treat more complex cases, including open bites,
Endowed Chair in Orthodontics, Texas A&M University College
crossbites, underbites, spacing, and even orthognathic
of Dentistry, Dallas, TX 75246, USA
(e-mail: phbuschang@tamu.edu) surgery cases.4,5
With the increasing popularity of clear aligners,
Accepted: July 2021. Submitted: March 2021.
Published Online: October 8, 2021 studies have been conducted to assess their limita-
Ó 2022 by The EH Angle Education and Research Foundation, tions. It has been shown that aligners are ineffective for
Inc. intruding teeth or extruding posterior teeth.6–8 Derota-

DOI: 10.2319/032921-246.1 173 Angle Orthodontist, Vol 92, No 2, 2022

174 LIN, JULIEN, KESTERKE, BUSCHANG

tion of teeth is one of the most difficult movements with of 4 mm or less, and no missing teeth (from the
clear aligners, especially for canines and premolars second molar to the second molar).
that are cylindrical.1,7,9,10 Part of the problem appears to  Exclusion criteria: anterior or posterior crossbite,
have been ClinCheck, which overestimated the anterior or lateral open bite, maxillary overjet
amount of rotation and tooth movement that occur.7,10,11 exceeding 4 mm, and impacted teeth.
Studies evaluating benefits have found that patients
Of the 80 patients, two had no final models, four had
treated with clear aligners have better periodontal
no final panoramic radiographs, five dropped out before
health, better hygiene, and lower oral bacterial counts
the completion of treatment, and three had no initial
than their counterparts wearing braces.12–15 Clear cephalogram (Figure 1). The Invisalign patients were
aligner patients also have less severe root resorption

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26.7 (IQR: 9.8) years old and the braces patients were
and less discomfort than patients with braces.16–18 25.9 (IQR: 16.6) years old at the start of treatment.
Treatment duration can also be shorter with clear Among the patients who completed the study, 24 were
aligners than with braces.16,19 male and 42 were female. There were 32 Invisalign and
Studies comparing treatment outcomes of Invisalign 34 braces patients with complete records at the end of
and fixed appliances have been inconsistent. A treatment. Of those who completed treatment, 54
comparison of non-extraction treatments showed no returned for their 6-month retention visit, including 26
statistically significant between-group differences in Invisalign and 28 braces patients.
the peer assessment rating (PAR) index or compo-
nents of the PAR.19 Another study showed that Sample Allocation
Invisalign patients had significantly higher objective
grading system (OGS) scores at the end of treatment Power analyses were performed using descriptive
than patients treated with traditional braces.1 Both statistics previously reported for Invisalign treatment
studies evaluated differences immediately after treat- outcomes.3,20 The analysis assumed a clinically mean-
ment had been completed, making it impossible to ingful group difference of 10 OGS points, which has
determine whether settling could have occurred. The been used by the American Board of Orthodontics
only comparison that included retention visits was a (ABO) for distinguishing between acceptably and
cohort study showing that alignment, as measured by unacceptably treated cases. Using an alpha error of
the OGS, was significantly worse at the end of 0.05, it was estimated that 31 subjects per group were
treatment among Invisalign than traditionally treated needed to achieve a power of 90%, with an effect size
patients.20 Importantly, all three studies were retro- of 0.8. An Excel spreadsheet was used to generate the
spective and none of the comparisons were based on random assignment of patients to treatment groups
patients treated after 2010, when Invisalign introduced (Invisalign or fixed appliances). The study was ap-
SmartForce features and attachments that have been proved by the institutional IRB #2012-21-BCD-FB, and
informed consent was obtained from all patients and
claimed to allow for more accurate and a wider range of
parents. The study was registered at the National
tooth movements.
Institutes of Health Clinical Trials website.
The purpose of the present study was to compare
patients treated with traditional braces to patients
Treatment Protocols
treated with Invisalign that incorporated SmartForce
features and attachments. To minimize bias, the All patients were treated in the Orthodontics Depart-
design was prospective, the patients were randomized, ment at Texas A&M College of Dentistry by an ABO-
and the observer was blinded. certified orthodontist. A series of custom-made clear
aligners was fabricated for each patient. The patients
MATERIALS AND METHODS were instructed to wear their trays 22 hours per day
and to change trays every 2 weeks. Patients were
Data Collection evaluated at 4-week intervals. A full set of diagnostic
The present study was designed as a randomized records were taken at the first appointment. At the
controlled trial. Eighty patients were recruited from second appointment, an intraoral scan was taken using
screenings at the Graduate Orthodontic Clinic of Texas an iTero scanner (Align Technology, Tempe, AZ) and
A&M College of Dentistry and advertisements on the sent to Align Technology. The ClinCheck (Invisalign)
school website. To be selected for the study, patients digital models were used to fabricate a treatment plan.
had to meet the following criteria: If correction of malocclusion was deemed to be
unsatisfactory, patients were brought in for a refine-
 Inclusion Criteria: Class I molar and canine relation- ment scan to fabricate additional aligners. All aligner
ships, non-extraction treatment, mandibular crowding patients had at least one refinement scan, but no one

Angle Orthodontist, Vol 92, No 2, 2022

CASE QUALITY OF INVISALIGN VS TRADITIONAL BRACES 175

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Figure 1. Flow diagram of patients enrolled in the present study.

had more than two refinement scans. Each refinement maxillary and mandibular teeth at the second appoint-
increased treatment time by approximately 4 weeks. At ment. Adjustment appointments were scheduled every
the debond appointment, final records were taken. One 4 weeks until the malocclusions were corrected. Once
month after the completion of treatment, patients were good occlusion had been achieved, brackets were
seen for a retainer check and new photographs were debonded and final records were taken. One month
taken. At the 6-month retention check visit, another set after the completion of treatment, patients were seen
of records was taken. for a retainer check and photographs. At the 6-month
The traditional fixed appliances consisted of 0.018 3 retention check visit, another set of alginate impres-
0.028-inch Radiance MBT (American Orthodontics, sions and photographs was taken.
Sheboygan, WI) brackets on the upper arch and
Alexander prescription brackets on the lower arch. Retention
The cases were all finished in 17325 stainless steel
wires. A combination of elastic O-rings and stainless After the completion of treatment, patients were
steel ligatures was used to tie the archwires to the retained with upper wrap-around Hawley and lower
brackets. Fixed appliances were bonded to the extended Gemini retainers. If severe lower incisor

Angle Orthodontist, Vol 92, No 2, 2022

176 LIN, JULIEN, KESTERKE, BUSCHANG

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Figure 2. Box whisker plot of treatment duration. Figure 3. Box whisker plot of discrepancy index (DI) scores.

irregularity was present at pretreatment, patients were Statistical Methods

also retained with bonded lower 3-3 fixed retainers. If a
diastema was present at the start of treatment, patients Based on the skewness and kurtosis statistics, the
were retained with an additional bonded upper 2-2 variables were not normally distributed. The variables’
fixed retainer. Thirteen patients received both a central tendencies and dispersion were described
bonded lower 3-3 and an upper 2-2 fixed retainer, using medians and interquartile ranges (IQR). The
including 12 braces patients and 1 Invisalign patient. Mann-Whitney U-test was used to evaluate differences
Thirty-seven patients received just a bonded lower 3-3 in treatment times, total ABO-OGS scores, and
retainer: 17 braces patients, and 20 Invisalign patients. component scores.
One braces patient received only an upper 2-2 fixed
retainer. In total, 29 braces patients and 22 Invisalign RESULTS
patients received fixed retention. Average treatment times from initial records to
debond for the Invisalign and braces groups were 1.7
Evaluations years (IQR: 0.7) and 1.3 years (IQR: 0.7), respectively
Three time points were included in this study: T0 (Figure 2), which was a statistically significant differ-
ence (P , .001). Patient ages and posttreatment
(initial), T1 (final), T2 (6 months retention).
duration showed no statistically significant between-
Each patient’s initial Discrepancy Index (DI) was
group differences (Table 1).
assessed using the patients’ T0 cephalograms and
models.21 The primary outcomes of this study were the
Group Comparison
ABO-OGS scores, including the component and
overall scores at T1 and at T2.22 The secondary The median DI scores for the Invisalign and braces
outcome was the between-group differences in treat- group at the start of treatment were 4.5 (IQR: 6.0) and
ment time (T0-T1). 7.0 (IQR: 5.0), respectively (Figure 3). This difference
All cephalograms for DI calculations were digitally was statistically significant (P , .05).
traced by one blinded investigator using Dolphin Imaging At the end of treatment (T1), the Invisalign group had
software. Examiner reliability was based on eight better alignment, occlusal contacts, overjet, and root
randomly selected sets of records that were scored again angulation scores, while the braces group had better
after 2 weeks. Reliability of over 90% was achieved. marginal ridge scores (Table 2). Buccolingual inclina-

Table 1. Invisalign (INV) and Fixed Orthodontic Appliance (FOA) Patient Ages (Years) at Initial (T0), End of Treatment (T1), 6-Month Recall (T2)
Appointment, as Well as the Duration Between Appointments a
Aligner Group Braces Group Difference
Time Points (Years) Median IQR Median IQR P Value
T0 Age 26.7 23.1; 32.9 25.9 23.4; 39.1 .778
T1 Age 28.6 24.7; 35.4 27.1 24.8; 40.5 .672
T2 Age 28.1 24.8; 37.7 27.6 24.8; 37.7 .849
Tx time (T0-T1) 1.7 1.5; 2.2 1.3 1.1; 1.8 ,.001
Retention (T1-T2) 0.5 0.4; 0.5 0.5 0.4; 0.5 .646
a
IQR indicates interquartile range.

Angle Orthodontist, Vol 92, No 2, 2022

CASE QUALITY OF INVISALIGN VS TRADITIONAL BRACES 177

Table 2. Medians and Interquartile Ranges (IQR) of OGS Scores at the End of Treatment (T1)a
Aligner Group Braces Group Difference
OGS Component and Overall Scores Median (50%) IQR (25%; 75%) Median (50%) IQR (25%; 75%) P Value
Alignment 2.0 1.0; 4.75 3.0 1.0; 4.0 .770
Marginal ridges 2.0 1.0; 2.0 1.0 0.0; 2.25 .472
Buccolingual inclination 2.0 1.0; 3.0 2.0 2.0; 4.0 .158
Occlusal contacts 1.0 0.0; 4.75 2.0 0.0; 3.25 .532
Overjet 1.0 0.0; 3.0 2.5 0.0; 6.0 .286
Interproximal contacts 0.0 0.0; 0.0 0.0 0.0; 0.0 .719
Root angulation 0.0 0.0; 1.0 1.0 0.0; 2.0 .127

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Occlusal relations 2.0 0.0; 4.0 2.0 1.0; 5.25 .219
OGS 12.0 7.0; 25.0 17.0 11.75; 23.75 .158
a
OGS indictes objective grading system.

tion, interproximal contacts, and occlusal relationships occlusal relations improved. The marginal ridges,
of the two groups were very similar at T1. There were buccolingual inclination, occlusal contacts, overjet,
no statistically significant between-group differences at interproximal contacts, and root angulation of the
T1. Overall OGS scores at the end of treatment were aligner patients changed minimally. None of the OGS
12.0 (IQR: 18.0) and 17.0 (IQR: 12.0) for the Invisalign component scores showed statistically significant
and braces groups, respectively, a difference that was between-group posttreatment differences. Between
not statistically significant. the end of treatment (T1) and the 6-month recall visit
At the 6-month retention visit, the Invisalign group (T2), total OGS scores did not change for the aligner
scored better for buccolingual inclination, occlusal group and decreased for the braces group, but the
contacts, overjet, root angulation, and occlusal rela- difference was not statistically significant.
tionships, while the group braces scored better for
alignment and marginal ridges (Table 3). There were DISCUSSION
almost no differences between the two groups for
interproximal contacts. Again, none of these differenc- Braces patients in the present study finished 4.8
es were statistically significant. The overall OGS months earlier than the aligner patients. Invisalign
scores of the Invisalign and braces groups at the 6- patients have previously been reported to finish 3.6-
month recall were 12.5 (IQR: 9.25) and 14.5 (IQR: 5.53,16,19 months faster than braces patients. The longer
12.5) for, respectively, a difference that was not treatment times with aligners in the present study could
statistically significant (P ¼ .367). have been related to the 2-week intervals between
Between T1 and T2, braces patients showed trays, compliance, and refinements. All of the patients
improvements in buccolingual inclination, occlusal started treatment with Class I molars and canines,
contacts, and occlusal relationships, but only the minimal crowding, no major overjet, and no open bites,
alignment and buccolingual inclination changes were which negated the need for anteroposterior and vertical
statistically significant (Table 4). Braces patients corrections. This minimized patient compliance among
exhibited minimal changes for marginal ridges, overjet, the braces patients because they did not have to wear
interproximal contacts, and root angulation. The elastics. In contrast, the aligner patients had to wear
alignment and overjet of the aligner patients worsened their appliances, making their lack of compliance a
significantly, but their buccolingual inclinations and greater likelihood and extending the treatment times of

Table 3. Medians and Interquartile Ranges (IQR) of OGS Scores at the 6-Month Recall (T2)
Aligner Group Braces Group Difference
OGS Component and Overall Scores Median (50%) IQR (25%; 75%) Median (50%) IQR (25%; 75%) P Value
Alignment 3.5 2.0; 5.5 3.0 2.0; 5.75 .993
Marginal ridges 1.5 0.0; 2.0 1.0 0.0; 2.0 .474
Buccolingual inclination 1.0 0.0; 2.25 2.0 0.0; 2.0 .586
Occlusal contacts 0.0 0.0; 2.25 1.0 0.0; 2.0 .373
Overjet 2.0 1.0; 5.25 3.0 1.0; 4.75 .740
Interproximal contacts 0.0 0.0; 0.0 0.0 0.0; 0.0 .209
Root angulation 0.0 0.0; 1.0 0.50 0.0; 2.0 .050
Occlusal relations 1.5 0.0; 4.0 2.5 0.25; 5.0 .289
OGS 12.5 8.0; 17.25 14.5 9.25; 21.75 .367
a
OGS indictes objective grading system.

Angle Orthodontist, Vol 92, No 2, 2022

178 LIN, JULIEN, KESTERKE, BUSCHANG

Table 4. Medians and Interquartile Ranges (IQR) of OGS Score Changes Between End of Treatment (T1) and the 6-Month Recall (T2)a,*,**
Aligner Group Braces Group Difference
OGS Component and Overall Scores Median (50%) IQR (25%; 75%) Median (50%) IQR (25%; 75%) P Value
Alignment 1.0** 0.0; 2.0 0.0* 0.0; 1.0 .307
Marginal ridges 0.0 1.0; 0.0 0.0 1.0; 0.0 .897
Buccolingual inclinations 0.0* 1.25; 0.0 1.0* 2.75; 0.0 .274
Occlusal contacts 0.0 2.0; 0.0 1.0 2.0; 0.0 .823
Overjet 0.0* 0.0; 1.0 0.0 0.0; 1.0 .551
Interproximal contacts 0.0 0.0; 0.0 0.0 0.0; 0.0 .113
Root angulation 0.0 0.0; 0.0 0.0 0.0; 0.0 .000

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Occlusal relations 1.0* 2.0; 0.25 0.50 1.75; 0.0 .578
OGS 0 4.5; 2.0 1.5 5.75; 2.75 .677
Probability of within-group changes over time [*prob ,.05;** prob ,.01].
a
OGS indicates objective grading system.

at least some individuals. In addition, previous aligner appliance removal.20 Both their study and the present
studies did not specify whether there were refinements. study showed no significant changes in the total OGS
The Invisalign patients in the present study had 1-2 score, with a limited number of significant changes in
refinements, which could have added weeks to months the component scores, between the end of treatment
onto treatment duration. and post-retention. This indicates that the components
The initial case difficulty cannot explain the differ- of occlusion that improved were offset by other
ence in treatment times. Each point increase of the DI components that worsened over time, essentially
is thought to increase treatment duration by 11 days.23 negating any changes of the total OGS score.
However, the braces patients in the present study Both groups in the present study showed worsening
started treatment with significantly higher DI scores of alignment and overjet from T1-T2, and improve-
(7.0) than the aligner patients (4.5) and, yet, they ments in buccolingual inclination and occlusal relation-
finished 4.8 months faster without the adjustment, and ships. Aligner and braces patients followed 3 years
more than 7 months faster after the adjustment. It is posttreatment showed more pronounced worsening of
important to emphasize that, even though the between- alignment than the present study and no change in
group difference in the DI was statistically significant, it buccolingual inclination.20 The smaller changes ob-
was small. Based on ABO discrepancy index guide- served in the present study could have been due to the
lines, a DI score of 7-15 is considered mild, 16-24 is
duration of the posttreatment period or to the low initial
moderate, and scores 25 are considered to be
DI score for aligner patients. Nett et al., who evaluated
severe.3
100 randomly chosen patients not treated with align-
At the end of treatment, the present study showed no
ers, also reported significant worsening of alignment
significant between-group differences in the total OGS
and improvement of buccolingual inclinations after a
score, or for any of the component scores. Kuncio et al.
minimum of 10 years post-retention.24 Together, these
also found no differences between braces and aligners
findings suggest that the posttreatment changes
in OGS scores or component scores.20 In contrast,
braces patients have been shown to end treatment observed for the aligner cases were not treatment-
with significantly better posttreatment buccolingual related.
inclination, occlusal contacts, occlusal relationships, The cases in the present study had excellent
overjet, and total OGS scores than aligner patients.3 treatment results. The overall and component OGS
The difference between this and the present study scores were much lower than those previously
could be that, due to initial case complexity, their reported after treatment and post retention. For
starting DI scores were 14.1 and 12.9 points higher example, Djeu et al. had average total OGS scores
than the aligner and braces patients in the present of 45.4 and 32.2 for aligners and braces patients,
study, respectively. It is also possible that the different respectively.3 Kuncio et al. had average total OGS
outcomes were due to the newer materials and scores of 39.5 and 43.0 for aligner and braces patients,
technologies used to treat the Invisalign patients in respectively.20 The present study had median total
the present study. OGS scores of 12.0 and 17.0 for aligner and braces
The present study also showed that there were no patients, respectively. The present study also found
between-group differences 6 months post-retention. much lower component scores than previously report-
Kuncio et al. also found no statistically significant ed in the literature, partially reflecting the fact that the
between-group differences in OGS scores 3 years after cases were initially simpler.

Angle Orthodontist, Vol 92, No 2, 2022

CASE QUALITY OF INVISALIGN VS TRADITIONAL BRACES 179

CONCLUSIONS 11. Ke Y, Zhu Y, Zhu M. A comparison of treatment effective-

ness between clear aligner and fixed appliance therapies.
 Invisalign patients with simple Class I malocclusions, BMC Oral Health. 2019;19–24.
treated with SmartForce features and attachments, 12. Rossini G, Parrini S, Castroflorio T, Deregibus A, Debernardi
require 4.8 months longer treatment times than CL. Periodontal health during clear aligners treatment: a
patients with simple malocclusions treated with systematic review. Eur J Orthod. 2014;37:539–543.
traditional braces. 13. Jiang Q, Li J, Mei L, et al. Periodontal health during
orthodontic treatment with clear aligners and fixed applianc-
 For simple Class I malocclusions, aligners produce
es. J Am Dent Assoc. 2018;149:712–720.
the same excellent occlusal results as traditional 14. Abbate G, Caria M, Montanari P, et al. Periodontal health in
braces at the end of treatment. teenagers treated with removable aligners and fixed

Downloaded from http://meridian.allenpress.com/angle-orthodontist/article-pdf/92/2/173/3015542/i1945-7103-92-2-173.pdf by Indonesia user on 04 August 2023

 For simple Class I malocclusions, there are no orthodontic appliances. J Orofacial Orthop. 2015;76:240–
differences in occlusal results between aligners and 250.
braces 6 months posttreatment. 15. Karkhanechi M, Chow D, Sipkin J, et al. Periodontal status of
adult patients treated with fixed buccal appliances and
removable aligners over one year of active orthodontic
REFERENCES therapy. Angle Orthod. 2013;83:146–151.
16. Buschang PH, Shaw SG, Ross M, Crosby D, Campbell PM.
1. Rossini G, Parrini S, Castroflorio T, Deregibus A, Debernardi Comparative time efficiency of aligner therapy and conven-
CL. Efficacy of clear aligners in controlling orthodontic tooth tional edgewise braces. Angle Orthod. 2014;84:391–396.
movement: a systematic review. Angle Orthod. 2015;85: 17. White DW, Julien KC, Jacob H, Campbell PM, Buschang
881–889. PH. Discomfort associated with Invisalign and traditional
2. Melsen B. Northcroft Lecture: how has the spectrum of brackets: a randomized, prospective trial. Angle Orthod.
orthodontics changed over the past decades? J Orthod. 2017;87:801–808.
2011;38:134–143. 18. Almasoud NN. Pain perception among patients treated with
3. Djeu G, Shelton C, Maganzini A. Outcome assessment of passive self-ligating fixed appliances and Invisalignt align-
Invisalign and traditional orthodontic treatment compared ers during the first week of orthodontic treatment. The
with the American Board of Orthodontics objective grading Korean J Orthod. 2018;48:326–332.
system. Am J Orthod Dentofac Orthop. 2005;128:292–298. 19. Gu J, Tang JS, Skulski B, et al. Evaluation of Invisalign
4. Taub DI, Palermo V. Orthognathic surgery for the Invisalign treatment effectiveness and efficiency compared with
patient. Sem Orthod. 2017;23:99–102. conventional fixed appliances using the Peer Assessment
5. Kankam H, Madari S, Sawh-Martinez R, Bruckman KC, Rating index. Am J Orthod Dentofac Orthop. 2017;151:259–
Steinbacher DM. Comparing outcomes in orthognathic 266.
surgery using clear aligners versus conventional fixed 20. Kuncio D, Maganzini A, Shelton C, Freeman K. Invisalign
appliances. J Craniofac Surg. 2019;30:1488–1491. and traditional orthodontic treatment postretention outcomes
6. Khosravi R, Cohanim B, Hujoel P, et al. Management of compared using the American Board of Orthodontics
overbite with the Invisalign appliance. Am J Orthod Dentofac Objective Grading System. Angle Orthod. 2007;77:864–869.
Orthop. 2017;151:691–699. 21. Cansunar HA, Uysal T. Relationship between pretreatment
7. Charalampakis O, Iliadi A, Ueno H, Oliver DR, Kim KB. case complexity and orthodontic clinical outcomes deter-
Accuracy of clear aligners: a retrospective study of patients mined by the American Board of Orthodontics criteria. Angle
who needed refinement. Am J Orthod Dentofac Orthop. Orthod. 2014;84:974–979.
2018;154:47–54. 22. Cangialosi TJ, Riolo ML, Owens S, et al. The ABO
8. Duncan LO, Piedade L, Lekic M, Cunha RS, Wiltshire WA. discrepancy index: a measure of case complexity. Am J
Changes in mandibular incisor position and arch form Orthod Dentofac Orthop. 2004;125:270–278.
resulting from Invisalign correction of the crowded dentition 23. Parrish LD, Roberts WE, Maupome G, Stewart KT, Bandy
treated nonextraction. Angle Orthod. 2016;86:577–583. RW, Kula KS. The relationship between the ABO discrep-
9. How accurate is Invisalign in non-extraction cases? Are ancy index and treatment duration in a graduate orthodontic
predicted tooth positions achieved? Brit Dent J. 2018;224: clinic. Angle Orthod. 2011;81:192–197.
156–156. 24. Nett BC, Huang GJ. Long-term posttreatment changes
10. Papadimitriou A, Mousoulea S, Gkantidis N, Kloukos D. measured by the American Board of Orthodontics objective
Clinical effectiveness of Invisalignt orthodontic treatment: a grading system. Am J Orthod Dentofac Orthop. 2005;127:
systematic review. Prog Orthod. 2018;19:37. 444–450.

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