Transverse Maxillary discrepancy

Abstract

Transverse maxillary deficiency is a common problem among orthodontic patients.

Orthopedic and orthodontic forces are used to correct transverse maxillary deficiency

(TMD) in young patients. Correction of TMD in a skeletally mature patient is carried out

by Surgically assisted rapid palatal expansion (SARPE). The aim of this article is to present a

comprehensive review of the literature, including diagnosis, etiology, indications for

maxillary expansion, an overview of Slow maxillary expansion, Rapid maxillary Expansion

, Surgically assisted rapid palatal expansion, Stability and Retention of Maxillary expansion.

Introduction

Transverse maxillary deficiency is characterized by narrow maxilla in relation to the rest of

the craniofacial structures, and narrow palatal vault. Transverse maxillary deficiency leads to

crossbite, anteroposterior discrepancies, dental crowding, and airway problems. The

etiologies of transverse maxillary deficiency are numerous. It can be due to both genetic and

environmental factors, soft tissue influences, cleft palate, and habits.1 Different treatment

modalities used to correct Transverse maxillary deficiency are , slow maxillary expansion

,Rapid maxillary expansion (RME),Surgically assisted Rapid maxillary expansion (SRME)

etc. Selection of appliance is based on the age of patient, nature of the discrepancy, etiology

and type of malocclusion.

Growth of Mid Palatal Suture

The midpalatal suture develops at about 12 weeks in utero.

According to a study by Snodell et al55 The transverse dimension is the first to reach adult

size, followed by sagittal and vertical. It is known that the midpalatal suture does not fuse

until somewhere between the ages of 15-18 years on average and even older in some cases.
56
Bjork found that age 17 was the average age in which the median suture fused. Melsen
found growth of the suture of the maxilla to fuse at age 16 years in females and 18 years 5 in

males, while Snodell et al. found that transverse growth was completed for the majority of

females at age 15 and 17 years for males. 55This is important in the timing of rapid maxillary

expansion treatment, as it is expected to be successful in patients that have not reached the

age in which their midpalatal suture has fused. Implant studies by Bjork and Skieller state

that a greater amount of transverse growth posteriorly than anteriorly. 56

Etiology of transverse discrepancies:

Transverse maxillary deficiency can be dental or skeletal in origin or a combination of both.

Likewise, the discrepancy may originate in the maxilla or the mandible or a little of both.

Haas makes an important point in distinguishing true maxillary deficiency from relative

maxillary deficiency.6,7

Etiology of TMD 50
Palatal dimensions and inheritance 15,16

Iatrogenic (cleft repair) 12,13,14

Cleft lip and palate 19,20

Muscular8-11,17

Habits–thumb sucking 8-11

Obstructive sleep apnea8-11

Klippel-Feil syndrome18

Marfan syndrome20

Duchenne muscular dystrophy17

Non-syndromic palatal synostosis21

Osteopatia striata22

Treacher Collins22

Multifactorial
Diagnosis There is much literature on the various methods used to diagnose the maxillary

transverse deficiency. Clinical evaluation, model analysis, occlusograms, and radiographic

measurements have been recommended for an accurate assessment.50

Clinical evaluation includes assessment of the maxillary arch form and symmetry, shape of

the palatal vault, width of the buccal corridors on smiling, Unilateral or bilateral crossbite,

severe crowding, and predominant mode of breathing , The soft-tissue thickness should also

be evaluated because it can mask TMD. Another factor that needs assessment is a mandibular

shift on closure. This can often be a chin deviation with a unilateral crossbite.23,24

Study models should be used to assess the arch form and the shape and make specific

measurements to evaluate for TMD. Several indices have been proposed to measure lateral

discrepancies. The most common include the indices of Pont, Linder-Harth, and Korkhaus. 25.

The digital model are also useful in diagnosis, It can be viewed in desired cross-sections that

permit better visualization of the buccolingual inclination of the teeth, It can also generate

images for occlusograms.26,27

Lehman et al28 recommended a palatal or an occlusal radiograph as an essential tool to

evaluate the ossification of the midpalatal suture. This, however, is unreliable because of the

superimposition of other bony structures on the midpalatal suture .

Betts et al29 suggested that postero-anterior cephalograms are the most readily available and

reliable means to identify and evaluate transverse skeletal discrepancies between the maxilla
30
and the mandible, Using cephalometric landmarks as described by Ricketts, The advent of

3-dimensional imaging techniques is the most recent tool for diagnosis that has enabled an

accurate visualization of the craniofacial region. It also allows for evaluation of the spatial

relationships of various areas of the jaws.31

INDICATIONS FOR MAXILLARY EXPANSION

The clinical situations in which maxillary expansion should be considered are:

Crossbites: Unilateral and bilateral crossbites.

Distal Molar Movement

Headgear is often used to distalize the maxillary molars in order to increase arch length for

the relief of crowding and overjet reduction. During distal molar movement, it is important

that the intermolar distance is also increased, so that a crossbite is not created in the molar

region as a narrower part of the upper arch is moved back against a wider part of the lower

arch. Expansion in these cases can be achieved by slightly expanding the inner bow of the

headgear,32

Functional Appliance Treatment

Functional appliances are commonly used in the treatment of moderate Class II malocclusion

in growing patients. In the majority of cases, it is important to expand the maxillary arch

during treatment in order to maintain arch co-ordination as the maxillary dentition is

distalized relative to the mandibular dentition. The amount of expansion required can be
judged by asking the patient to bite the incisors in an edge-to-edge position and noting the

size of the transverse discrepancy that develops in the buccal segments

A number of techniques can be used to increase inter-molar width during functional

appliance treatment, including use of a midline expansion screw (e.g. the Twin Block

appliance), and buccal shields (The Function Regulator appliances of Frankel). 32

Surgical Cases

Arch expansion may be indicated in a number of joint orthodontic-orthognathic cases in order

to maintain arch coordination following correction of the sagittal skeletal discrepancy. 32

Maxillary Protraction

Rapid maxillary expansion may be used to facilitate maxillary protraction using reverse pull

headgear as it disrupts the circummaxillary sutures, It can be used for the management of

skeletal Class III malocclusion in growing patients.

Mild Crowding : Maxillary expansion may be used in carefully selected cases for the relief

of mild crowding.

TECHNIQUES AVAILABLE FOR MAXILLARY EXPANSION

Rapid maxillary expansion

Rapid maxillary expansion (RME) is one of the most frequent methods used by orthodontics

to treat this problem. RME is based on the concept of widening the dental arch by means of

opening the mid palatal suture. The concept dates back to 1860 when Angell described rapid

expansion in a paper to the dental community. RME produces expansion that is 50% dental

and 50% skeletal. 41

 Factors to be considered prior to RME 4

1. Discrepancy between maxillary and mandibular first molars & bicuspid width is more

than 4mm is indicated.

2. Severity of cross bite: i.e number of teeth involved.

3. Initial angulation of molars or premolars

4. Assessment of roots of deciduous tooth

5. Physical availability of space for expansion.

6. Rate of expansion

Expansion of dental arch increases as rate of expansion is increased.

7. Form of expansion

Effect of expansion increases as rigidity is increased

8. Age of patient

Effect of expansion diminishes as age advances.

Tooth borne RME Appliances

HYRAX TYPE

43
Use of special type of screw HYRAX (Hygienic rapid expander) which consist of

heavy gauge wire extensions adapted to follow palatal contour and are soldered to

bands on premolars and molars ,can produced expansion of 11 mm in very less period

of time ,each activation of screw produced 0.2 mm of lateral expansion.

ISAAC SON TYPE

Spring loaded screw - MINNE expander (Developed at university of Minnesota Dental

school) are used and First premolars and molars are banded. Metal flanges - soldered to

bands - buccal and lingual sides. Coil spring made to extend between the lingual metal

flanges. Activated by closing the nut. 43

Tooth and tissue born

HAAS TYPE

First premolar and molar of either side banded , 0.045 inch length SS wire is welded and

soldered in buccal and palatal aspects of bands. Lingual wire is kept long and extends

anteriorly and posteriorly. Extension are bent palatally and embedded in palatal acrylic.

Produced expansion in 10-14 days.7 Force produced up to 3-10 pounds.

Derichsweiler type

First premolars and first molars are banded. Wire tags are soldered onto

palatal aspect of bands. Wire tags get inserted into split palatal acrylic plate with

screw at its centre.

The principle advantage of the banded appliance is that oral hygiene is facilitated . The

Haas appliance has palatal flanges, which contact the palatal mucosa, through which

expansion forces are transmitted directly to the skeletal structures. However, cleaning is very

difficult. The bonded appliance can be easily cemented during the mixed dentition stage,

when retention from other appliances can be poor. The buccal capping is thought to limit

extrusion of the molars during treatment and therefore improve overbite control.40

Mode of action

RME produces expansion by a greater degree of skeletal movement and less tipping of the

molars. Wertz 44 found that approximately 40% of the expansion achieved could be attributed

to skeletal changes. The ratio between anterior to posterior skeletal expansion was

approximately 2:1 and the greatest skeletal response was achieved when treatment was

carried out before or during puberty. The posterior maxilla expands less readily because of

the resistance produced by the zygomatic buttress and pterygoid plates. In long-term, it

appears that there is continual relapse even up to five years after initial treatment. 45

Clinical Management of RME

Activation schedule: Schedule by Timms46 : Patients of upto 15 years of age, 90° rotation

in the morning and evening. In patients over 15 years, Timms recommends 45° activation 4

times a day.

Schedule by Zimring and Isaacson :

In young growing patient, two turns each day for 4-5 days and later one turn each day till the

desired expansion is achieved.

In case of non growing adult patients, two turns each day for first two days, one turn per day

for next 5-7 days and one turn every alternate day till the desired expansion is achieved.43

Active treatment is usually required for a period of 2–3 weeks, after which a retention period

of three months is recommended to allow for bony infilling of the separated suture. During

retention, a ligature wire can be tied around the expansion screw to prevent it turning

inadvertently.32

Effect of RME on The Maxillary Complex

Structure Effect of RME

 Maxillary halves  The two halves of the maxilla rotated in both the
sagittal and frontal planes

Palatal vault  Maxilla displaced downward and forward 7.

Alveolar process  The palatal vault height decreased significantly

during RME

 lateral bending of the alveolar processes occurs

early during RME 34.

Circummaxillary sutures  Increased width in the intermaxillary,

internasal, maxillonasal, frontomaxillary, and
frontonasal sutures.57

Maxillary teeth  Midline diastema between 1/1

Posterior Teeth show buccal tipping and
believed to extrude to a limited extent 5

Effects of RME on the mandible  RME could lead to a concurrent expansion of

the lower arch as much as 4 mm in inter-canine
width and 6 mm in inter-molar width 47

Effects of RME on nasal volume  Nasal width and volume increases by RME 48
changes

Effect of RME on soft tissue  Nihat Kilic and et al , concluded in their study
that the soft tissue facial angle decreases and the
H angle and profile convexity increases after
RME 49

SURGICAL TECHNIQUES

Surgically assisted expansion techniques can be considered in skeletally mature individuals

with significant transverse discrepancies.

The techniques available include:

- Surgically Assisted Rapid Palatal Expansion (SARPE);

- Segmental maxillary surgery.

SARPE

The main resistance to maxillary skeletal expansion comes from the buttressing effect of the

zygomatic and sphenoid bones at their point of attachment to the maxilla and from the

integrity of the midpalatal suture. With SARPE, these attachments are surgically severed

which allows expansion to be easily achieved using a conventional RME appliance. Fixed

appliances can be used to move apart the roots of the central incisors before surgery so that

the roots are not damaged by the midline maxillary cuts. Expansion is typically carried out at

a rate of 0.5 mm a day and patients develop a significant midline diastema. Surgical

expansion has a high relapse tendency, probably because of the inelasticity of the palatal

mucoperiosteum, and a degree of over correction is valuable. 32

Segmental Maxillary Surgery

Transverse expansion can be produced during a Le Fort 1 osteotomy by creating an additional

surgical cut along the midpalatal suture. The maxillary halves are then separated and retained

in the new position. The relative inelasticity of the palatal mucoperiosteum limits the degree

of expansion that may be achieved. Before surgery, orthodontic treatment involves moving

the roots of the maxillary central incisors apart to improve surgical access to the osteotomy

site. This is the technique of choice in patients who require expansion and have co-existing

sagittal and/or vertical maxillary discrepancies32,

Slow Maxillary expansion(SME)

Slow maxillary expansion produced less tissue resistance around the circummaxillary

structures and, therefore improved bone formation in the intermaxillary sutures, which

reduced the limitations of RME.

Slow expansion has been found to promote greater post expansion stability. 5,34 if given an

adequate retention period. It delivers a constant physiologic force . The desirable force level

is 400 g 450 to 900 gm , which may be insufficient to separate a progressively maturing

suture.4, 5,32,33.Maxillary arch width increases ranged from 3.8 to 8.7 mm with slow expansion

of as much as 1 mm per week.

Slow maxillary expansion Appliance

Coffin spring

Given by Walter coffin 1975.It is a Removable appliance capable of slow dento alveolar

expansion. Consist of omega shape wire of 1.25 mm thickness, placed in mid palatal

region.The spring is activated by pulling two asides apart manually.

W –ARCH

Originally used by rickets to treat cleft palate conditions . 35 It is constructed of 36 mil

steel wire soldered to molar bands . The w –arch is activated simply by opening the

apices of w- arch and is easily adjusted to provide more anterior than posterior
 expansion, or vice versa . The appliance delivers proper force levels when opened 3-4mm

wider than the passive width and should be adjusted to this dimension before being

inserted .40

The Quadhelix Appliance

The quadhelix appliance is a modification of Coffin’s W-spring and was described by

Ricketts.36 The incorporation of four helices into the W-spring helped to increase the

flexibility and range of activation. The length of the palatal arms of the appliance can be

altered, depending upon which teeth are in crossbite. The appliance is retained by

orthodontic bands which are cemented with glass ionomer cement onto the first permanent

Molars.

Mode of Action

The quadhelix appliance works by a combination of buccal tipping and skeletal expansion in

a ratio of 6:1 in prepubertal children.37

Clinical Management
The desirable force level of 400 g can be delivered by activating the appliance by

approximately 8 mm, which equates to approximately one molar width. Patients should be

reviewed on a six-weekly basis. A three-month retention period, with the quadhelix in place,

is recommended . 32

NiTi Expander

The nickel titanium expanders were introduced by Wendell V 38 , generates optimal, constant

expansion forces . Its central component is fabricated from a thermally activated nickel

titanium alloy, The rest of the appliance, including the anterior arms, is made of stainless

steel. The nickel titanium component has a transition temperature of 94°F 39 . At room

temperature, the expander is too stiff to bend for insertion. Chilling the expander softens the

central component, allowing easy manipulation. A 3mm increment of expansion exerts only

about 350g of force, and the nickel titanium alloy provides relatively uniform force levels as

the expander deactivates. 40

The Spring jet

The active components of the spring Jet are soldered or attached to the molar bands as with

any traditional expander. The transpalatal arch is replaced by a telescopic unit with a nickel

titanium coil spring and a lock screw. Activation of the coil spring is achieved simply by

moving the lockscrew horizontally along the telescopic tube. A ball stop on the transpalatal

wire allows the spring to be compressed.

The telescopic unit is placed 5mm up from the center of the molar bands, so that the line of

force passes close to the center of resistance of the maxillary teeth. Two different coil springs

are available using the 240g spring in the mixed dentition and the 400g spring in the

permanent dentition.40

Removable Appliances

A removable appliance, with a midline expansion screw, is a popular device for achieving

maxillary expansion. Expansion is produced predominately by tipping the molar teeth

buccally. A very small amount of skeletal expansion, by separation of the mid-palatal suture,

may be expected in prepubertal children.

The patients should be instructed to turn the expansion screw a quarter turn (0.2 mm

expansion) once a week. Following expansion, the appliance is used as a retaining appliance

for at least three months. However, they do rely on patient cooperation. 32

EXPANSION WITH FIXED APPLIANCES

Expansion with Archwires

Significant expansion may be produced by using overexpanded stainless steel archwires,

particularly those with a large dimension (for example, 0.021" x 0.025"). The archwire

should be over expanded by approximately 10 mm. 32

Auxiliary Arches

Expansion arches, also known as jockey arches, are auxiliary wires incorporated into a fixed

appliance during treatment. The expansion arch, which can be made from 0.019" x 0.025"

rectangular stainless steel or a larger round steel wire with a diameter of 1–1.13 mm, runs

over the main archwire and is inserted into the extra-oral traction tubes of the first molar

bands posteriorly and secured anteriorly with a ligature 32

Self-Ligating brackets- The Damon System

The Damon System is a passive self-ligation system that was invented by Dr. Dwight

Damon.52 Damon System’s ability to achieve transverse arch development helps minimize the
51
need for tooth extractions and procedures such as rapid palatal expanders or surgery. the

necessary expansion can be achieved by the force of the archwires.52

Pandis et al.53 found that conventional and self-ligating brackets alleviate crowding by lower

incisor proclination and slight expansion of the dental arches . The intermolar width gained

in the Damon2 bracket reached 1.5 mm above the value of conventional appliances. The

difference in posterior expansion may be solely attributed to the differences in the archwire

forms and cross-sectional thicknesses.

STABILITY OF CROSSBITE CORRECTION

The factors which may be important in enhancing the stability of maxillary

expansion include:
 - Achievement of good intercuspation;

- Alteration in tongue position.

Expanding the maxilla in some cases may allow the tongue to adopt a higher resting position

which may help to maintain increases in transverse arch dimensions; Mode of respiration.

Expansion may be less stable in mouth breathers because of the lower natural tongue

position. 32

Retention: Retainers should be constructed from acylic and the Hawley type is

recommended. The more flexible Essix type of retainer may not have adequate rigidity to

counteract relapse forces. 32

CONCLUSIONS

Maxillary transverse Deficiency can be treated successfully by proper diagnosis and

treatment planning. Review of literatures suggest different mechanisms for expansion. The

precise method selected will depend on the nature of the crossbite (i.e. skeletal versus dental),

the size of the discrepancy, the age of the patients and other factors related to the dentition

(e.g. amount of dento-alveolar compensation). There are chances of high relapse potential in

transverse expansion, so it is important to achieve a degree of over correction and provide

adequate retention.

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