Orthodontic Diagnosis And Treatment In Transverse Dimension • In orthodontics, among the three planes of space - sagittal, vertical, and transverse, the transverse is the least studied. • The transverse facial growth normally completes before the sagittal and vertical growth. • Understanding the transverse growth is important in making proper diagnosis and treatment planning of the transverse problems.

1. Diagnosis And Treatment In
The Transverse Dimension
Arun Bosco Jerald
2018 Batch

2. Contents
• Introduction
• Transverse skeletal growth
• Maxilla
• Mandible
• Maxillary and mandibular dental arches
• Buccolingual inclination changes of
molars with growth
• Etiology of Transverse Problems
• Diagnosis of Transverse Problems
• Presentation
• Maxillomandibular Transverse
Differential
• Transpalatal width
• Andrews’s WALA ridge
• CBCT evaluation
• Posterior cross bites
• Terminologies
• Classification
• Algorithm for treatment decisions
• Maxillary expansion
• Rationale for expansion treatment
• General indication of the expansion
• Contra-indications of maxillary
expansion
• Techniques & appliances

3. • Growth Modification in Transverse Plane
• Palatal Expansion in the Primary and
Early Mixed Dentition
• Palatal Expansion in Preadolescents
• Palatal Expansion in Adolescents
• Rapid Palatal Expansion
• Slow Palatal Expansion
• Alternative Expansion Approaches
• Surgically assisted rapid palatal expansion
• Implant-Supported Expansion
• Maxillary Expansion and Sleep-Disordered
Breathing
• Clinical Management of Palatal Expansion
Devices
• Treatment of Transverse Mandibular
Constriction
• Restriction of Excessive Transverse Growth
• Conclusion
• References

4. Introduction
• In orthodontics, among the three planes of space - sagittal, vertical, and
transverse, the transverse is the least studied.
• The transverse facial growth normally completes before the sagittal and
vertical growth.
• Understanding the transverse growth is important in making proper
diagnosis and treatment planning of the transverse problems.
• Malocclusion in the transverse plane has a prevalence of 8-16% in the
primary dentition (Foster & Hamilton 1969) and 9-24% in Adults (Helm S.
1968).
• 8-18% of referred pts have maxillary transverse deficiency. (Gill et al.,
2004)

5. • The presence of facial asymmetry, anteroposterior jaw differences, insufficient
buccal overjet and compensation in the posterior area can all contribute to a
relative or absolute maxillary transverse deficiency.
• Treatment of transverse problems in the primary or early mixed dentition
can still utilize conventional tooth-borne rapid maxillary expansion
appliance.
• However, adolescent patient with more mature skeletal development may
require bone-borne anchorage for maxillary expansion.

6. • The gold standard for treatment of transverse deficiencies in adults is still
the use of Surgical Assistant Rapid Palatal Expansion (SARPE) appliance.
• With the advent of Temporary Skeletal Anchorage Device (TSAD), the
envelope of nonsurgical treatment of maxillary transverse deficiencies can
be increased to include the young adults.

7. Transverse skeletal growth of maxilla
• Transverse growth of Maxilla is explained by oppositional growth that
follows the “V” principle (Enlow, 1982) as well as sutural growth (Sicher
and Weinnman,1952) along the mid-palatal suture.
• It is the presence of this line of fusion that enables us to expand the
maxilla effectively.
• There are two components of maxillary growth - sutural and periosteal.
• The sutures involved in the maxillary growth are - frontomaxillary,
lacrymomaxillary, nasomaxillary, ethmoidomaxillary, zygomaticomaxillary,
intermaxillary (mid palatal) and vomeromaxillary.

8. • The total growth between 4 and 17 years amounts to ~7mm. (Bjork &
Skieller 1974).
• Bjork and Skieller (1977) conducted a longitudinal study and found that in
the maxillary molar region, most transverse skeletal growth is from
sutural growth, with a small amount from periosteal growth (bone
remodeling).
• In addition, more sutural growth was found in the molar region than in
the incisor region. Thus, there was a rotation of the two halves of maxilla.

9. • Ricketts et al. (1982) reported the transverse growth changes from age 9
to 16, for both genders, on PA cephalograms.
• The maxillary skeletal width was determined as the distance between the
left and right J (Jugale), which increased 0.6 mm per year. In a later study,
• Ricketts and Grummons (2003) reported in males, from age 3 to 21, an
increase in J-J distance,1 mm per year.
• In a longitudinal study on PA cephalograms of subjects from age 5 to 18,
Cortella et al (1977) » males had greater maxillary transverse dimensions
than females. In addition, the maxillary transverse growth (J-J) for females
completed at age 14, but for males it continued to about age18.

10. • Wagner and Chung (2005) found that there was a relationship between the
transverse growth and vertical facial type.
• At age 6, the dolichofacial (high mandibular plane angle) subjects had
smaller maxillary (J-J) widths than the brachyfacial (low mandibular plane
angle) subjects. This trend continued until age 18.

11. Transverse skeletal growth of mandible
• Transverse growth of Mandible is explained by oppositional growth that
follows the “V” principle.
• There are two types of growth in the mandible - cartilaginous and
periosteal. The condyles are the only places in the mandible having
cartilaginous growth, the rest of mandibular growth is periosteal growth
and remodeling.
• The basal bone under dental arch almost completes its width development
at the end of pubertal growth.
• However, the condyles continue to grow and the rami continue to remodel
after the growth spurt.

12. • Ricketts et al. (1982) reported the distance between the left and right Ag
(antegonion) increased 1.4 mm per year for both sexes.
• Ricketts and Grummons (2003) reported for males, the Ag-Ag distance increased
1.5mm per year.
• Cortella et al.(1977) reported, females completed mandibular growth at around
age 16, and males continued to age 18.
• Wagner and Chung (2005) reported at age 6, the high-angle group had smaller
mandibular (Ag-Ag) widths than the low-angle group. This trend continued
until age 18.
• It should be noted that the Ag was located at the angular area of ramus, which is
far from dentition and should not represent the mandibular basal bone.

13. Transverse growth of maxillary and
mandibular dental arches
• Moyers et al. (1976) reported that the mandibular intermolar width at the
first molars was established at age 12 for girls with no more changes after
that; for boys, the increase was only 1mm to age 18.
• For maxillary intermolar width, it was established at age 12 for girls; for
boys it increased 1.4 mm from age 12 to 18.
• For intercanine width, it was established for maxillary and mandibular
arches at age 12 for both genders.
• McNamara and Brudon (2001) reported that, genders combined, the transpalatal
width increased only 2.6 mm from age 7 to 15. After age 12, there was no change
on the transpalatal width.

14. Safety valve mechanism
• The intercanine width of maxilla acts as “ safety valve” .
• Postnatally the mandible grows comparatively more than the maxilla.
• However intercanine width of mandible is completed earlier to that of
maxilla which may extend upto 12-16 years.
• This may check the any abnormal horizontal growth of mandible that
occurs upto 18 years of age.

15. Buccolingual inclination changes of molars
with growth
• Wilson G H (1911) was first to report the mandibular molars being
inclined lingually and the maxillary molars being inclined buccally. (curve
of Wilson)
• Dempster et al. (1963) studied the arrangement of the roots of the teeth
and confirmed the lingual inclination of the mandibular posterior teeth.
• Bjork and Skiller’s implant study showed that with growth, maxillary
molars become more upright with buccal root torque. Also reported: with
growth, maxillary canines become more upright with buccal root torque.

16. • Measuring clinical crowns of molars on dental casts, Marshall et al.(2003)
and Sayania et al.(2017) showed that buccolingual inclination changes with
growth.
• Normally, maxillary molars erupt with buccal inclination and become more
upright with age; mandibular molars erupt with lingual inclination and
become more upright with age.
• In adults, the lingual cusps of maxillary molars are more occlusal than the
buccal cusps, and the buccal cusps of mandibular molars are more occlusal
than lingual cusps. Thus, the curve of Wilson is maintained.

17. Etiology of Transverse Problems
• Congenital ( Morphogenetic)
• Developmental
• Long term thumb sucking habit,
• Adenoid problem can cause a low tongue position with an increased
lower facial height and subsequent cross bite. Aronson (1972) ,
Solow and Tallgren 1969 had suggested that this effect may be
produced as a result of mouth breathing or Airway obstruction
• Due to an anterior-posterior discrepancy resulting in relative cross bite
• Traumatic; Pathology of the TMJs
• Iatrogenic (Repaired Cleft lip & palate)

18. • Cleft lip & palate is a unique case where the congenital malformation leads
to a transverse discrepancy of expanded arch while its correction leads to
an iatrogenic constriction.
• Transverse discrepancies with congenital etiology as in the case of
syndromes are associated with genetically determined morphogenetic
patterns and are difficult to manage.

19. • On the other hand discrepancies with developmental etiology are
associated with environmental factors and respond well to interventions.
• Sagital skeletal discrepancies often manifest as transverse discrepancies. A
Class III skeletal malocclusion with maxillary retrognathism for instance
will present with a posterior crossbite as a narrow part of an arch is
occluding with a wider opposite arch.
• Interestingly the first report of rapid maxillary expansion by Emmerson
Colon Angell (1860) was in a case of Class III skeletal malocclusion

20. Diagnosis of Transverse Problems
Presentation
• A transverse discrepancy has diverse presentation.
• Midline shifts of greater than 2mm.
• Single tooth cross-bite.
• Unilateral or Bilateral posterior crossbite
• These can further be either Dentoalveolar or skeletal. A posterior crossbite
involving more than two teeth is likely to have a skeletal component
(Jacobs JD et al, AJODO 1980).

21. • Unilateral posterior crossbite can present with or without functional
displacement of mandible. There is wide consensus that unilateral
posterior cross bites with mandibular displacement require definitive
management as their persistence leads asymmetric muscle activity and
altered bite force in children.
• A bilateral crossbite can present as an unilateral crossbite due to a
“convenience swing” of the mandible. Hence assessment of transverse
dimension should be done both in CR (Centric relation) as well as CO
(Centric occlusion).

22. • Other clinical signs include:
• crowded, rotated and palatally or buccally displaced teeth
• narrow tapering maxillary arch form
• high palatal vault
• excessive buccal corridors

23. Transverse occlusal deviations

25. • Howe RP, McNamara JA Jr, O’Connor KA, AJODO 1983;
• The distance between the closest points of the upper first molars (ie,
transpalatal width) be measured.
• Typically a maxillary arch with a transpalatal width of 36 to 39 mm can
accommodate a dentition of average size without crowding or spacing,
• Whereas maxillary arches less than 31 mm in width may be crowded and
thus in need of orthopedic or surgically assisted expansion

26. Maxillomandibular Transverse Differential
• In 1999, Vanarsdall proposed it as a diagnostic tool for transverse skeletal
problems.
• The method was based on the Ricketts et al’s norms (Rocky Mountain
Analysis) of maxillary and mandibular growth measured from PA
cephalograms.
• The maxillary skeletal width (J-J) and mandibular skeletal width (Ag-Ag)
of patient are measured on a PA cephalogram and compared with the
norms of Ricketts’ et al.
• The maxillomandibular width difference (Ag-Ag and J-J) of the patient
and difference of Ricketts’ norms of the same age (Ag-Ag and J-J) were
calculated and compared.

27. • Normally the difference should be within 5 mm. If it is more than 5 mm, a
transverse skeletal problem exists.
• The limitation of this method is that the landmark Ag is far back from the
dentition and may not be an accurate landmark to be used to determine the
skeletal transverse width of the basal bone.
• In addition, there was no consensus on what the norms of transverse
skeletal widths (J-J, Ag-Ag) are for males and females determined from PA
cephalogram. Several reported studies have shown that this analysis was
not sensitive enough to detect the transverse problems.

28. Transpalatal width
• Is determined from the gingival margin of lingual groove of the first
molar to the first molar of the other side.
• As mentioned earlier, McNamara and Brudon reported the mean normal
values from age 7 to 15.
Age Mean transpalatal width
7 32.7 ± 1.4 mm
8 33.2 ± 1.5 mm
9 33.2 ± 1.4 mm
10 33.7 ± 1.5 mm
11 34.5 ± 1.4 mm
12 35.2 ± 1.4 mm
12-15 No change

29. • The patient’s transpalatal width can be compared with the reported values to
determine if the upper arch is normal.
• Cautions should be made when using this method, since the norms are combined
with both genders and the dental compensations (buccolingual inclination) are
not considered.
• Moreover, the transpalatal width may be affected by vertical facial types.
• Isaacson et al.(1971) reported that the width of palate (distance between the
mesiolingual cusp tips of the first molars) increased as the mandibular plane
angle (MP – SN) decreased.
• Forster et al.(2008) reported male arch widths were significantly larger than
those of females. For both males and females, there was a trend that as MP – SN
angle increased, the arch width Decreased.

30. Andrews’s WALA ridge
• When evaluating the dental casts, Andrews (2015) suggested that the
primary landmark for assessing mandibular arch width and shape is the
WALA Ridge.
• The WALA is an acronym for Will Andrews and Larry Andrews, who
defined the ridge as the most prominent portion of a mandible’s
mucogingival junction.
• Andrews suggested that when an optimal mandibular arch is viewed from
the occlusal perspective, the distance of FA point (center of facial axis of
the crown) of the first molar to WALA Ridge should be 2mm.

31. • In this position, the mandibular first molars are decompensated, and the
arch width between the central fossae of the mandibular first molars is the
optimal mandibular arch width.

32. • For the maxilla, the occlusal plane on the maxillary first molars should be
parallel to the transverse plane of the head from the frontal perspective.
• In this position, the maxillary first molars are decompensated and the
distance between the mesiolingual cusp tips of the right and left maxillary
first molars should be equal to the distance between the mandibular right
and left central fossa.
• It should be noted that since the diagnosis is made on the dental casts, the
root positions in the alveolar bone are not known unless a 3- dimensional
image such as a CBCT is taken.

33. CBCT evaluation
• When examining using CBCT on the transverse
dimension, normally there should be proper
skeletal widths of maxilla and mandible and a
harmonious relationship.
• The roots of teeth are positioned in the center
of alveolar bones, the maxillary molars slightly
incline buccally and mandibular molars slightly
incline lingually.

34. • Miner et al.(2012) reported that in normal occlusion, at the mid alveolar
bone levels of lingual surfaces of the first maxillary and mandibular first
molars, the maxillary width is about 1.2 ± 2.9 mm less than mandibular
width with a wide range.
• For a narrow skeletal maxilla without dental crossbite, the maxillary
posterior teeth tend to compensate and incline buccally, and mandibular
posterior teeth tend to compensate and incline lingually.
• So, the palatal width at the mid-root level of maxilla is significantly less
than that of mandible. As a result, a significant curve of Wilson takes
place.

35. • For a wide skeletal maxilla without crossbite, the
maxillary posterior teeth tend to compensate and incline
lingually, and mandibular posterior teeth tend to
compensate and incline buccally.
• The palatal width at the mid-root level of maxilla is
significantly wider than that of mandible.
• As a result, a reverse curve of Wilson appears.
• The conventional PA cephalogram cannot detect these
problems.

36. Yonsei transverse index (YTI) – center of resistance perspective
• Kee-Joon Lee et.al, Sem in Ortho, 2018
• An estimated center of resistance was used to represent the transverse
position of the posterior segment from the CBCT
• The transverse widths at the crown or the estimated center of resistance
were measured and compared.
• The average difference between the maxillary and mandibular transverse
widths at the estimated center of resistance was -0.39±1.87 mm

38. Posterior cross bites
• Majority of posterior cross bites in children are associated with
mandibular displacement.
Displacement: When there is a discrepancy between the muscular
positioning of the mandible (centric position) and that dictated by the
teeth coming into occlusion (centric occlusion), the mandible encounters
a deflecting contact and it is displaced. Displacements can be anterior,
posterior or lateral.
• Establishing the presence or absence of mandibular shift therefore is an
important aspect of evaluation. The midlines in CR and in CO are to be
assessed. This takes us to two terminologies of significance.

39. • Latero-occlusion –Dental midlines coincide at postural rest position (CR)
but shift in occlusion (Habitual occlusion).
This is indicative of a dental prematurity and an associated
mandibular shift. It is extremely important to evaluate this in mixed
dentition.
• Laterognathy – Dental midlines do not coincide both in postural rest
position (CR) as well as in occlusion (CO).
This is indicative of a true transverse discrepancy, either
dentoalveolar or skeletal.

40. Classification of posterior crossbites
1. Unilateral Crossbite with Displacement
Clinical features
In most cases, the crossbite is accompanied by a mandibular shift, a so called forced
crossbite, which causes midline deviation
There is evidence of asymmetric muscle activity and altered bite force in children with a
posterior crossbite with displacement
Treatment options
1. Encourage habit to stop
2. Selective grinding of the primary canine success rate 27-90% (Harrison and Ashby,
2008 Cochrane)
3. Posterior onlay
4. Extraction if it is associated with severely displaced single tooth
5. Expand upper arch (Harrison and Ashby, 2008 Cochrane)

41. 2. Unilateral crossbite with no mandibular displacement
• Usually due to underlying skeletal asymmetry eg unilateral cleft, unilat. Condylar
hyperplasia
• Correction is seldom indicated
• Surgery for severe cases is indicated
3. Bilateral Crossbite
• Usually associated with a skeletal discrepancy in transverse, AP or both
• Usually there is no displacement & no functional indication for treatment
• Best treated with RME but you do get a lot of relapse » overcorrect
• Care should be taken to avoid the development of iatrogenic unilateral cross bite
with displacement post expansion.
4. Posterior mandibular displacement >This associated with Cl II D2 and better to
be treated ASAP to avoid TMJ problem

42. Algorithm for treatment decisions in transverse discrepancies
Posterior crossbite in centric occlusion
Assess occlusion in centric relation
CR=CO and bilateral
posterior crossbite
CR≠CO. bilateral posterior
crossbite in CR and shift to
unilateral crossbite in CO
CR=CO and unilateral
posterior crossbite
Result of either bilateral
maxillary arch constriction/
bilateral mandibular arch
expansion or combination of
both
Result of either asymmetric
maxillary
constriction/asymmetric
mandibular expansion or
combination of both

43. True unilateral posterior crossbite
Unilateral maxillary arch constriction Single
tooth or multiple teeth
Unilateral mandibular arch expansion
single tooth or multiple teeth
skeletal dental skeletal dental
Relatively rare
isolated occurrence-
typically part of
some syndromic
craniofacial anomaly
requiring complex
treatment planning
Asymmetric
dental
expansion
If severe- surgical
unilateral
mandibular
constriction
If not severe,
then orthodontic
camouflage
Orthodontic
unilateral
mandibular arch
constriction

44. Bilateral posterior crossbite
Bilateral maxillary arch constriction Bilateral mandibular arch expansion
skeletal skeletal
dental dental
Before mid-palatal
suture fusion
After mid-palatal
suture fusion
Orthopedic
maxillary
expansion by
using RME
If severe, then
surgical
maxillary
expansion
If not severe,
then
orthodontic
camouflage
Orthodontic
maxillary
dental arch
expansion
If severe, surgical
mandibular
constriction
If not severe,
then orthodontic
camouflage by
tipping
mandibular
posterior teeth
lingually
Orthodontic
mandibular
dental arch
constriction,
Possible when
interdental
spaces are
present.

45. Maxillary expansion
Rationale for expansion treatment
• Is to increase the distance between the two sides of the maxillary arch.
• This is achieved via:
1. Buccal tipping or bodily movement of the teeth
2. Separation of the mid-palatal suture, with induction of new bone formation.
• The aim of RME is to produce a greater degree of skeletal change.
• This is achieved by the use of a rigid appliance to limit tipping of the molars, and
the application of heavy forces very rapidly, so as to exceed the rate of dental
movement and produce splitting of the suture.
• The relative amounts of these changes vary depending on factors such as the
type of appliance used, rate of activation, and the age of the patient.

46. General indication of the expansion
1. Unilateral crossbite with displacement– Harrsion and Ashby 2001
2. Interceptive treatment of an ectopic canine (Armi & Baccetti, 2011)
3. To provide space in mild to moderate crowding
• 1mm of arch expansion in the molar region gives ~0.6mm of space for relief of
crowding (O’Higgins & Lee2000).
• So 3mm of expansion would allow relief of ~2mm of crowding without changing
the inclination of the labial segments.
4. Adjunctive to
• Functional appliances
• Molars distalization appliance to avoid potential posterior cross bite at the end
(expansion by inner bow HG or URA)
• Reverse facial mask treatment.
5. V shaped arch in a 'thumb-sucker’
6. Combined orthodontic surgical cases for arch coordination
7. Pre-bone graft in CLP patients

47. Contra-indications of maxillary expansion
1. Uncooperative patient
2. In a periodontally weak dentition
3. Severly buccally tipped teeth
4. High angle & reduced overbite
5. Convex profile
6. True skeletal asymmetry, Bishara 2001
7. Large amount of expansion required

48. Techniques &
appliances
0.9 mm SS expanded jockey

49. Growth Modification - Transverse Plane
• Customarily, treatment occurs by opening the midpalatal suture, as if on a
hinge superiorly at the base of the nose and also opens more anteriorly
than posteriorly.
• The expansion sometimes moves the maxilla forward a little (but is about
as likely to lead to backward movement), increases space in the arch, and
repositions underlying permanent tooth buds as they move along with the
bone in which they are embedded.
• Adequate expansion that coordinates the arches will also eliminate
mandibular shifts and interferences.
• Palatal expansion can be done at any time before the end of the adolescent
growth spurt, but the technique varies with the patient’s age, with
different procedures for preadolescents, early and late adolescents, and
adults.

50. Palatal Expansion in the Primary and Early Mixed Dentition
• Skeletal expansion is easiest when the midpalatal suture has not fused or
has only minor initial bridging, so that heavy force and extensive
microfracturing are not needed to separate the palatal halves.
• Almost any expansion device will tend to separate the midpalatal suture in
addition to moving the molar teeth in a child up to age 9 or 10.
• Three methods can be used for palatal expansion in children:
(1) a split removable plate with a jackscrew or heavy midline spring,
(2) a lingual arch, often of the W-arch or quad-helix design, or
(3) a fixed palatal expander with a jackscrew, which can be either attached to
bands or incorporated into a bonded appliance.

51. • With a split removable plate, the rate of
expansion must be quite slow, and the
force employed during the process must be
low because faster expansion produces
higher forces that create problems with
retention of the appliance.
• Multiple clasps that are well adjusted are
mandatory.
• Because of the instability of the teeth
during the expansion process, failure to
wear the appliance even for 1 day requires
adjustment of the jackscrew.

52. • Lingual arches of the W-arch and quad-
helix designs have been demonstrated to
open the midpalatal suture in young
patients.
• Generally deliver a few hundred grams of
force and provide slow expansion.
• Are relatively clean and reasonably
effective, producing a mix of skeletal and
dental change that approximates one-third
skeletal and two-thirds dental change.
• There is some evidence that these appliances are more effective than removable
appliances as well as more comfortable for the patient and more efficient.

53. • Fixed jackscrew appliances attached to bands or bonded splints also can be
used in the early treatment of maxillary constriction,

54. • But in comparison with an expansion lingual arch, two major disadvantages.
• First, a jackscrew appliance bulky and more difficult to place and remove.
• The patient inevitably has problems cleaning it, which leads to soft tissue
irritation, and either the patient or parent must activate the appliance.
• Banding permanent molars and primary second molars is relatively simple,
but banding primary first molars can be challenging.
• Use of a bonded jackscrew appliance in the mixed dentition is relatively
straightforward, but it can be difficult to remove if conventional bonding
techniques are used.
• Second, an appliance of this type can be activated rapidly, which in young children
is a disadvantage and can cause facial distortion

55. Rapid palatal expansion in young children can lead to undesirable changes in the nose, as in this 5-year-
old who had expansion at the rate of 0.5 mm per day (two quarter turns of the jackscrew per day).
(A) Nasal contours before treatment. (B) Jackscrew appliance after activation over a 10-day period.
(C) and (D) Nasal hump and paranasal swelling, which developed after the child complained of
discomfort related to the expansion.

56. • There is no evidence of any advantage of rapid movement and high forces
in children, and ample evidence that this can be dangerous.
• On balance, slow expansion with an active lingual arch is the preferred
approach to maxillary constriction in children with primary and early
mixed dentitions.
• A fixed jackscrew appliance is an acceptable alternative if activated
carefully and slowly. In fact, 10 years after treatment, both rapid and slow
palatal expansion, although sometimes used for different magnitudes of
constriction, have been found to be stable.
• It also appears that anteroposterior dental changes in terms of overjet are
not consistently correlated with maxillary expansion.

57. Palatal Expansion in Preadolescents (Late Mixed Dentition)
• With increasing age, the midpalatal suture becomes more and more tightly
interdigitated.
• By the late mixed dentition period, sutural expansion often necessitates
placement of a relatively heavy force directed across the suture, which
microfractures the interdigitated bone spicules so that the halves of the
maxilla can be moved apart.
• A fixed jackscrew appliance (either banded or bonded) is necessary.
• As many teeth as possible should be included in the anchorage unit.
• In the late mixed dentition, root resorption of primary molars may have
reached the point at which these teeth offer little resistance, and it may be
wise to wait for eruption of the first premolars before beginning
expansion.

59. • Many functional appliances for Class II treatment incorporate some
components to expand the maxillary arch, either intrinsic force-generating
mechanisms such as springs and jackscrews or buccal shields that reduce
cheek pressure against the dentition.
• When arch expansion occurs during functional appliance treatment, it is
possible that some opening of the mid-palatal suture contributes to it, but
the precise mix of skeletal and dental change is not well documented.
• Although some studies have reported increases in vertical facial height
with maxillary expansion, long-term evidence indicates this change is
transitory.

60. • A bonded appliance that covers the occlusal surface of the posterior teeth
may be a better choice for a preadolescent child with a long-face tendency
because it produces less mandibular rotation than a banded appliance, but
in the long term, this is not totally clear
• Perhaps the best summary is that the older the patient when maxillary
expansion is done, the less likely it is that vertical changes will be
recovered by subsequent growth.
• An important consideration in skeletal expansion is the rate of activation
of the expander, so that rapid or slow expansion is obtained.

61. • In the late mixed dentition, either rapid or slow expansion is clinically
acceptable, but simplicity and consideration for tissue irritation probably
favors slow expansion.
• It now appears that slower activation of the expansion appliance (at the
rate of <2 mm per week) provides approximately the same ultimate result
over a 10- to 12-week period as rapid expansion, with less trauma to the
teeth and bones

62. Palatal Expansion in Adolescents (Early Permanent Dentition)
• In mid-adolescence, there is a near-100% probability of opening the
midpalatal suture with a banded or bonded expansion device, but as the
adolescent growth spurt ends, interdigitation of the suture reaches the
point that opening it may no longer be possible.
• Guidance for decision making regarding the state of the midpalatal suture
could be gained from chronologic age or dental developmental age.
• Or, it could be provided by one of several developmental staging methods
that have been proposed, such as cervical vertebra maturation staging
(CVMS)

63. Baccetti and Franchi (Angle orthodontist 2001 and Seminars in orthodontics
2005)
• Skeletal outcomes of greater magnitude and stability can be obtained
when the expander is used before the pubertal growth spurt (stages 1 to 3
of CVM).
• Transverse changes shift to dentoalveolar level when RME therapy is
performed after the after the pubertal peak (stages 4 to 6 of CVM)

64. • Another option is to use the five-stage midpalatal suture maturation
method. (Angelieri et al,2013)
• Recently, Grünheid et al (2017) tested several methods including those
mentioned earlier and a novel one called the “midpalatal suture density
ratio” (MSDR).
• The calculation used gray levels (really substitutes for bone density levels)
from CBCT images of defined palatal regions. The ratio values were 0 to
1, with 0 indicating less calcification and gray levels closer to soft tissue
and 1 indicating a more calcified suture with gray levels closer to palatal
bone.

65. • The values for MSDR, chronologic age, CVM, and stage of midpalatal
suture maturation were correlated with actual measurements of skeletal
expansion to determine which was a good predictor of the potential and
desired expansion.
• The results showed that only MSDR was significantly correlated and at a
high enough level to provide clinical value (by explaining about half the
variability).
• As CBCT images become more common as diagnostic aids in orthodontics,
this method may prove helpful in determining whether rapid, slow, or
surgical expansion is recommended.

66. • Skeletal anchorage for expansion is more likely to be successful in
adolescents, because retention of bone screws and plates requires a level
of bone maturation that is not reached until mid-adolescence.
• Presumably, objective measures of bone maturation such as MSDR could
be used to decide whether skeletal anchorage in the form of bone screws
on each side of the palate would be feasible.
• The later years of adolescence are when decisions regarding maxillary
expansion become most difficult. By the end of adolescence, for some
patients, there is no expansion for 1 or 2 days as each turn of the screw
increases the amount of force, until the patient hears and feels suture
fracture.

67. • For others, increasing pain from the amount of force against the teeth
leads to giving up on expansion after that amount of time.
• For these late adolescents, rapid expansion does make some sense, because
force builds up rapidly to the point at which either the suture fractures or
the treatment is discontinued.
• Slow expansion would be likely to just move the teeth, not open the suture.

68. • A modern view would be that for patients of this type, tooth-supported
expansion should not be attempted. Instead, micro-implant assisted
palatal expansion (MARPE) should be used, with one activation of the
screw (0.25 mm) per day, rather than using heavy force against the teeth.
• This approach along with surgically assisted palatal expansion (SARPE)
and segmental osteotomy of the maxilla are the possibilities for the more
mature patients in whom tooth-supported expanders will not work.

69. Rapid Palatal Expansion
• Major goals of growth modification always are to maximize the skeletal
changes and minimize the dental changes produced by treatment.
• Rapid palatal expansion (RPE) was recommended to help meet this goal.
• Was first proposed by Emerson Colon Angell in 1860. his findings were
rejected at that time and Andrew J Haas reintroduced the concept in 1961.
The appliance that we use today is primarily the design proposed by Haas
• The theory was that with rapid force application to the posterior teeth,
there would not be enough time for tooth movement, the force would be
transferred to the suture, and the suture would open up while the teeth
moved only minimally relative to their supporting bone.
• It is true in the first couple of weeks, but not thereafter

71. • With RPE at a rate of 0.5 mm per day
(two quarter turns of the screw), a
centimeter or more of expansion is
obtained in 2 to 3 weeks, with 10 to 20
pounds of pressure across the suture.
• Sometimes a large coil spring is
incorporated along with the screw, which
modulates the amount of force,
depending on the length and stiffness of
the spring

72. • Most of the movement is separation of the two halves of the maxilla, but
force also is transmitted to adjacent posterior structures.
• A space between the central incisors develops because the suture opens
wider and faster anteriorly and suture closure begins in the posterior area
of the midpalatal suture.
• The space created at the midpalatal suture is filled initially by tissue fluids
and hemorrhage, and at this point the expansion is highly unstable.
• The expansion device must be stabilized so that it cannot screw itself back
shut and is left in place for 3 to 4 months. By then, new bone has filled in
the space at the suture, and the skeletal expansion is stable.

74. • The midline diastema decreases and may disappear during this time.
• The diastema closes from a combination of skeletal relapse and tooth
movement created by stretched gingival fibers, not from tooth movement
alone.
• The aspect of rapid expansion that was not appreciated initially was that
orthodontic tooth movement continues after the expansion is completed,
until bone stability is achieved.
• In most orthodontic treatment, the teeth move relative to a stable bony
base.

75. • It is possible, of course, for tooth movement to allow bony segments to
reposition themselves while the teeth are held in the same relationship to
each other, and this is what occurs during the approximately 3 months
required for bony fill-in at the suture after rapid expansion.
• During this time, the dental expansion is maintained, but the two halves
of the maxilla move back toward each other as a result of soft tissue
forces, which is possible because at the same time the teeth move laterally
on their supporting bone.

76. • After the 3-month retention period, the
fixed appliance can be removed, but a
removable retainer that covers the palate is
often needed as further insurance against
early relapse.
• A relatively heavy, expanded maxillary
archwire provides retention and support if
further treatment is being accomplished
immediately.
• If not, a transpalatal lingual arch or a large expanded auxiliary wire (36 or 40
mil) in the headgear tubes will help maintain expansion while a more flexible
wire is used in the brackets.

77. According to Bishara-
• whether to expand the dental arches conventionally or with RME:
(1) The magnitude of the discrepancy between the maxillary and
mandibular first molar and premolar widths; if the discrepancy is 4
mm or more, one should consider RME
(2) The severity of the crossbite, that is, the number of teeth involved
(3) the initial angulation of the molars and premolars—
• when the maxillary molars are buccally inclined, conventional
expansion will tip them further into the buccal musculature; and if
the mandibular molars are lingually inclined, the buccal movement
to upright them will increase the need to widen the upper arch.

78. Appliances used for RME
• Important features-
• Rigidity
• Flexibility may result in tilting of the dentoalveolar elements
buccally.
• Number of teeth included
• Incorporate as many teeth as possible- wider force distribution
reduces the load on individual teeth and hence reduces the damage
• Also aids in appliance retention

79. • Expansion mechanism used
• Spring or a screw can be used, but a spring reduces the rigidity and
control.
• Screw with a sufficient length is better.
• Hygiene
• Minimal coverage of the dental and palatal tissues and least amount of
interconnecting material.

80. Classified into
• Removable
• Removable expansion plates are not recommended if significant skeletal changes are
required.
• Midpalatal splitting with such appliances is possible, but not predictable. For these
appliances to be effective, they must be used in the deciduous or early mixed
dentition and must have sufficient retention to be stable during the expansion phase.
• Fixed
• Banded
• Tooth and tissue borne
• Tooth borne
• Bonded

81. • Fixed, banded, tooth and tissue borne-
• Hass type
• A length of .045 inch stainless steel wire is welded
and soldered along the palatal aspects of the bands.
The free ends are turned back and embedded in the
acrylic base which stops short of the bands and the
teeth. A screw is set in the midline of the split
acrylic base.
• Derichsweiler type
• Tags are welded and soldered to the palatal aspects
of the bands to provide attachments for the acrylic
which is also extended to the palatal aspects of all
non banded teeth except the incisors.

82. • The advocates of the tissue-borne fixed appliance (HASS) believe that it
causes a more parallel expansion force on the two maxillary halves and that
the force is more evenly distributed on the teeth and the alveolar processes.
The appliance is attached to the teeth with bands on the molars and first
premolars.
• However disadvantage is the pressure necrosis under the palatal mucosa.

83. Fixed, banded, tooth borne-
• Isaacson type-
• This appliance uses a special spring loaded screw called a MINNE
Expander which is adapted and soldered directly to the bands directly
with out the use of acrylic.
• The MINNE expander (Developed at Minnesota university dental
school) is a heavy caliber coil spring that is expanded by turning a nut
to compress the coil.
• Spring-loaded screws and the Minne expander may continue to exert
expansion forces after completion of the expansion phase unless they
are partially deactivated.

84. • Hyrax type-
• The hygienic appliance (Hyrax) is essentially a nonspring-loaded
jackscrew with an all wire frame. This frame is soldered to the bands
on the abutment teeth.
• The advocates of this appliance believe that it causes the least irritation
to the palatal mucosa and is easier to keep clean.
• Tooth extrusion, dental tipping, and an increase in the vertical
dimension are often encountered with expansion appliances.
• Bonded Hyrax using interocclusal acrylic may control the vertical
dimension and expand the maxillary halves in a more bodily and
symmetrical fashion

85. Banded Hyrax Bonded acrylic splint Hyrax

86. • Biedermann type :
• This appliance also required a special screw either Hyrax, Leone 620
or Unitek.
• These have extensions in heavy guage wire which are welded and
soldered to the palatal aspects of the bands.

87. Bonded appliances
• Cast cap splints
• These are usually cast in silver / copper alloy.
• The palatal extensions to receive the acrylic are cast integral with them.
• A specific screw is selected to give atleast 10mm of expansion
• Acrylic acts solely as a connecting agent b/w’n the cap splints and screws.
• Contact with the palatal walls in no way changes the expansion efficiency of
the appliance (Hershey et al 1976).

88. • Acrylic splints :
• Made of poly methyl metha-acrylate
• A wire framework may be adapted around the teeth to reinforce the acrylic.
• Mondro et al (1977)have described an all acrylic form of cap splints and inter
connection with a screw embedded in the midline.
• These splints are bonded to a teeth using either GIC (or) other bonding
adhesive, after adequate etching.

89. Activation schedule
• Zimring & Isaacson:
• In young growing patients, two turns each day for 4-5 days and later
one turn per day till desired expansion is achieved.
• In adults (non growing patients) two turns each day for first two days,
one turn per day for the next 5-7 days and one turn every other day till
desired expansion is achieved.
• Timms:
• Up to 15 yrs : 90° rotation once in the morning & once in the evening
• 15-20 yrs : 45° activation 4 times a day

90. Slow Palatal Expansion
• Slow activation of the expansion appliance at the rate of less than 2 mm
per week, which produces about 2 pounds of pressure in a child with
mixed dentition, opens the suture at a rate that is close to the maximum
speed of bone formation.
• The suture can show some opening on radiographs, but no midline
diastema appears.
• Even so, both skeletal and dental changes occur.
• With use of slow palatal expansion (one turn per day or every other day) in a
typical fixed expansion appliance or with use of a spring, effective
expansion with minimal disruption of the suture can be achieved for a
child with late mixed dentition.

91. • Two studies demonstrate age-appropriate approaches.
• Geran RG, McNamara JA, Baccetti T, et al, AJODO, 2006 :with patients who
averaged 8 years 10 months of age at the start, used a bonded acrylic splint and a
semirapid approach of 0.25 mm of expansion per day.
• McNamara JA, Baccetti T, Franchi L, et al. AO,2003, with patients averaging 12
years 2 months of age at the start, used a Haas-type RPE device turned twice for
0.5 mm of expansion per day of treatment.
• Both followed the expansion with retention, and ultimately the patients
underwent full treatment without further purposeful expansion.
• At the longterm evaluation points, the expansion across the molars and canines
and the increase in arch perimeter were quite similar, which indicates equivalent
long-term results.

92. Appliances used for SME
• Removable appliance with Jack Screw-
• The appliance is essentially the same as used for RME.
• The activation schedule varies such that the total expansion is 1 mm per
week.
• Multiple clasps that are well adjusted are mandatory.
• Because of the instability of the teeth during the expansion process, failure
to wear the appliance even for one day requires adjustment of the jack screw.

93. • Quad-helix
• has been extensively described and popularised by
Ricketts (1979).
• It is fabricated from 0.9mm SS wire and is either
soldered to the upper first molar or bent to fit into
a lingual sheath. The lingual arm of the appliance
extends to the premolar or cuspid.
• A removable or fixed quadhelix constructed of .040"
Blue Elgiloy for increased flexibility/ adjustability
and an Elgiloy based system called ORTHORAMA

94. • Removable nickel titanium versions have also been introduced which
may offer more favourable force delivery characteristics. But study
showed that the factor effect the efficiency of the system is the size of
the appliance and diameter of the wire not the material. Ingervall,1995
• The quad helix incorporates four helices that increase the wire length
and hence the flexibility and range of action.
• The posterior helix is beveled slightly to lay against the palatal vault
and is as close to the upper molar as possible.
• The anterior helices are brought as far forward as possible

95. • Intra-oral activation of quad-helix appliance.
• When an intraoral bend is made in the anterior segment to increase
the amount of overall expansion, a reciprocal bend must be made in the
posterior section in order to compensate for the tendency for mesial
rotation of the upper molars.
• Therefore, three intraoral adjustment bends are usually made at each
activation.
• Modification of the quad helix appliance

96. • Y plate:
• The acrylic sectioning is done in a Y shape. The
appliance incorporates two screws on each side.
• The incisor segment is expanded anteriorly
whereas the posterior segment moves laterally
• Coffin spring (1877, Walter coffin )
• Removable appliance incorporating omega shaped
loop bent with a wire of 1.25 mm thickness.
• The appliance is retained by means of Adam's
clasps. The free ends of the spring as well as
retentive arms of clasps are acrylised.
• Activation is done by using three prong pliers.

97. Expansion appliances utilizing NiTi
Various arch expansion devises incorporating NiTi have been developed
over past one decade.
• NiTi temperature activated palatal expander by W.V Arndt (1993)-
• Problems with RME-
• Less physiologic
• Intermittent forces
• Ineffective in correcting rotations of posterior teeth.
• Problems with SME
• Intermittent forces
• Ineffective in correcting rotations of posterior teeth

98. • To overcome the limitations of conventional expansion appliances
• Nickel titanium, temperature-activated palatal expander with the ability to
produce light, continuous pressure (230-300 grams) on the midpalatal suture
while simultaneously uprighting, rotating, and distalizing the maxillary first
molars was developed.
• The appliance has adjustable stainless steel extensions and is inserted into
standard horizontal lingual sheaths that are spot-welded to the molar bands.
A locking indent on the lingual attachment securely fastens the expander to
the molar band to ensure patient safety; an elastomer may be placed for even
more security

100. • The action of the appliance is a consequence of nickel titanium's
• shape memory and
• transition temperature effects.
• The nickel titanium expander has a transition temperature of 94°F. When
it is chilled before insertion, it becomes flexible and can easily be bent to
facilitate placement. As the mouth begins to warm the appliance, the metal
stiffens, the shape memory is restored, and the expander begins to exert a
light, continuous force on the teeth and the midpalatal suture

101. Degree of compression when
prototype appliance was chilled
below the transition temperature.
Effect of shape memory when the
appliance was warmed to body
temperature.

102. Rapid Maxillary Expansion in Cleft Lip and Palate Patients
• Because of their tendency toward skeletal segmental collapse, bilateral
complete cleft lip and palate patients often require rapid maxillary
expansion.
• In normal patients the opening of the midpalatal suture is evidenced by
the appearance of a diastema between the central incisors with suture
reorganization. In cleft patients, however, the separation occurs in the
suture between the maxilla and the premaxilla, with no osseous gain.
• As in normal individuals, the pattern of expansion is triangular, with a
greater opening in the anterior region.

103. • The expansion appliance produces orthopedic movement that separates the
maxillary bones and, to a lesser degree, tips the buccal teeth.
• The increase in maxillary arch width and the orthopedic effect can correct
the transverse maxillomandibular relationship.
• In growing individuals, the opening of the sutures can displace the maxilla
forward and downward, opening the bite and moving Point A anteriorly.
In most instances, however, these effects are only temporary

104. • Activation schedule-
• It is empirical but most commonly followed activation schedule is as
follows-
• The appliance is first activated with four quarter-turns 24 hours
after placement.
• For the next four days, the screw is activated two quarter-turns in
the morning and two quarter-turns in the evening.
• At this point, the orthopedic force should be sufficient, and
activation can be reduced to a more comfortable one quarter-turn in
the morning and one in the evening.

105. • The average activation period is from one to two weeks, depending on the
degree of maxillary constriction and the resistance of the patient's
maxillofacial structures.
• A 2-3mm overcorrection at the molars is recommended to counteract any
relapse tendency.
• Once the desired expansion is obtained, the screw is immobilized by
placing acrylic over it.
• The appliance is kept in place for three months of retention, which further
reduces the possibility of relapse

106. • Because of the high frequency of missing teeth and the tension of the
palatal scar tissue in these patients, it is often necessary to use removable
partial prostheses as permanent retainers.
• In some cases, fixed partial prostheses are placed

107. • RME will re-open the cleft as the maxillary segments are moved more
closely to their proper position
• A bone graft may be required to fill the hard tissue deficiency
• However this bone graft will not affect the stability of the resultant
occlusion and will not act as a strut against relapse.
• Expect some resorption, however well the graft was consolidated.

108. • RME in such patients produces less discomfort than in normal palate
subjects of equivalent age.
• As there is no mid-palatal suture
• In fact slightly less force is required to separate the maxillae in cleft
patients than in normal.
• Hence nickel titanium, temperature-activated palatal expander with
the ability to produce light, continuous pressure is very useful tool
for arch expansion in cleft patients.

109. Alternative Expansion Approaches
• Another expansion protocol with alternate rapid maxillary expansion and
constriction (Alt-RAMEC) was initially devised by Liou for treatment of
patients with Class III cleft palate with maxillary transverse and
anteroposterior deficiency.
• It requires the patient to alternatively expand and constrict the maxilla on
a weekly basis by 1 mm per day (two turns in the morning and two turns
in the evening for a weekly total of 7 mm) by using a double-hinged
expander.
• This is done for 7 to 9 weeks, then the patient wears a facemask for
maxillary protraction.
• The goal is to disrupt not only the midpalatal suture but also the lateral and
posterior sutures.

110. • whether this protocol has any application to expansion without protraction ?
• It appears from data obtained by using the Alt-RAMEC protocol with
noncleft children over a 9-week period that there was statistically significant
transverse change to the maxilla, adjacent sutures, and soft tissues, along
with approximately 1 mm of forward and downward movement at A point,
but not clinically different transverse changes from what one would see with
routine maxillary expansion.
• So, as a singular approach to maxillary expansion treatment alone, this is a
much more aggressive approach than is necessary, and carries risks

111. Surgically assisted rapid palatal expansion (SARPE)
• Brown introduced the concept of surgically assisted rapid palatal
expansion (SARPE) in 1938 and then SARPE procedure gradually became
the main treatment modality for adult patients with maxillary transverse
discrepancy.
• The original idea of surgically assisted expansion was that cuts in the
lateral buttress of the maxilla would decrease resistance to the point that
the midpalatal suture could be forced open (i.e., microfractured) in older
patients.
• Although this usually works in patients in their late teens or early 20s, the
chance of inadvertent fractures in other areas is a concern, especially for
patients in their 30s or older.

112. • For SARPE now, surgeons usually make all
the cuts needed for a Le Fort I osteotomy,
omitting only the final step of downfracture
• This allows widening of the maxilla against
only soft tissue resistance, manipulating the
osteotomy sites with what amounts to
distraction osteogenesis.
• If only expansion is desired, this provides a
somewhat less invasive approach than
segmental osteotomy.

113. • Some surgeons advocated a preliminary phase of SARPE before Le Fort I
osteotomy to move the maxilla anteroposteriorly or vertically.
• Current data, however, show that relapse of the dental expansion
accompanies SARPE and that its long-term stability is similar to that with
segmental osteotomy.
• The primary indication for preliminary SARPE is such severe maxillary
constriction that segmental expansion of the maxilla in the Le Fort I
procedure might compromise the blood supply to the segments.
• The advantages of treatment with SARPE were predictable skeletal and
dental changes and a low rate of relapse (5%~25%).

114. (A) Narrow maxillary arch, posterior crossbite, and maxillary incisor crowding before treatment.
(B) Expansion appliance in place after operation and activation of the screw over a period of 4 days after a brief latency
period, showing the amount of expansion that was obtained.
(C) Fixed appliance for completion of alignment. A compressed coil spring that was used to open space for the maxillary left
lateral incisor after the palatal expansion was removed 3 months after operation.
(D) Widening the maxilla corrected the posterior crossbite and provided space to align the incisors, which made it possible to
plan later cosmetic restoration of these stained teeth.
In this adult patient with maxillary
posterior crossbite and severe crowding,
SARPE was used to allow transverse
expansion that otherwise would not
have been possible. The modern surgical
technique includes all the bone cuts for a
Le Fort I osteotomy except the
downfracture.

115. Implant-Supported Expansion
• For older (more mature) adolescents, heavier force is needed to fracture the
suture.
• The chance that opening of the suture will occur with moderate force
declines with increasing bone maturity, and the chance increases that even
with heavier force, tooth-supported expanders will just move teeth rather
than open the suture.
• For these patients, initially rapid activation quickly leads to one of two
possible responses: The desired fracture occurs, or the patient is
experiencing significant pain.
• At that point the expansion screw should be backed off and surgical
assistance or very slow activation of an implant-supported expander
should be considered.

116. • From the perspective of patient management, it would be better to
consider a skeletally anchored expander from the beginning rather than go
through the aforementioned scenario.
• A randomized clinical trial at the University of Alberta in 2009 and 2010
compared the percentage of skeletal versus dental change with bone
screws at the base of the alveolar process versus conventional expansion.
• The result was no significant difference between the two groups, because
the alveolar process bent outward in the skeletal anchorage group.
• Since then, research has shown that bone screws in the palate provide
better anchorage and significantly less tooth movement, with a significant
difference between the palatally anchored and tooth-borne expanders.

117. • It must be kept in mind, however, the teeth do move apart as the suture
expands, and that the possibility of tooth movement allowing skeletal
relapse still exists—so the implant anchorage needs to remain in place for
2 to 3 months after the expansion is completed.
• At this point, the goal of treatment with skeletally anchored expanders is
not so much to provide heavy force as to apply the force directly against
the bone so that there is little or no pressure against the teeth.

119. • This provides a way to expand the maxilla in a patient with anodontia or
severe hypodontia, and would maximize skeletal change and minimize
tooth movement in patients with a normal dentition.
• Bone screws in the palate now are routinely used for expansion.
• With a jackscrew attached to skeletal anchors, rapid disruption of the
suture would be a disadvantage, so slow (<2 mm per week) rather than
rapid expansion is indicated.
• There are a number of designs for expanders, including hinged ones that
expand more anteriorly than posteriorly, and these can be adapted for
skeletal anchorage if desired

122. • Following midpalatal expansion, a retainer is needed even after bone fill-in
seems complete.
• Even with skeletal anchorage, the expansion increases the light but
constant pressure against the teeth from the stretched palatal mucosa and
soft tissues of the cheeks. Placing a blocking material to prevent the screw
from turning helps to retain the skeletal expansion, but dental relapse still
could occur.
• The general guideline is that after any type of maxillary expansion, the
fixed expansion device should remain in place until the new bone formed
in the midline suture has had time to calcify and at least partially mature,
and that a tooth-supported retainer is needed for another 6 to 12 months
after that.

123. • With RPE, the consensus is that a tooth-supported expansion appliance
should remain in place for 3 to 4 months and then can be replaced with a
removable retainer or other retention device.
• After slow expansion, the expansion device is not replaced with a tooth-
supported retainer for another 12 weeks after expansion is completed.
• With implant-supported expansion, the guideline is about the same as with
tooth-supported expansion.

124. Maxillary Expansion and Sleep-Disordered Breathing
• There is little doubt that nasal airway and nasopharynx volume are
increased by RPE (sometimes by an order of 2 when measured with CBCT
in children and adolescents).
• There is evidence that nasal resistance usually decreases when minimum
cross-sectional area and nasal volume are improved following expansion.
Compadretti GC et.al, 2006
• For patients with sleep-disturbed breathing and no adenotonsillar
hypertrophy, RPE appears to reduce Apnea– Hypopnea Index (AHI) and
arousal index scores. Pirelli P et.al, 2004

125. • Even in children with mild or severe tonsillar hypertrophy who showed
symptoms of sleep-disordered breathing, RPE produced a decreased AHI
that was sustained at 36 months. Villa MP et.al,2007, Villa MP et.al, 2011
• At this point, using true measures of respiration, RPE appears to have a
therapeutic effect for children and adolescents with sleep apnea.
• So, expanding those with normal palatal dimensions into buccal crossbite
is justified if resistance to nasal airflow is demonstrated.

126. Clinical Management of Palatal Expansion Devices
• Most traditional palatal expansion devices use bands for retention on
permanent first molars and first premolars if possible.
• During the late mixed dentition years, the first premolars often are not
fully erupted and are difficult to band.
• If the primary second molars are firm, they can be banded along with the
permanent first molars.
• Alternatively, only the permanent first molars can be banded and the
supporting framework extended anteriorly, contacting the other posterior
primary and erupting permanent teeth near their gingival margins.

127. • A comparison of four-band versus two-band devices showed that the four-
band devices provided more transverse expansion and arch perimeter,
especially after 12 years of age when the suture was more calcified.
Davidovitch M et.al, AJODO, 2005
• If first premolars are available, they should be banded.
• Expanders with hinged designs can differentially expand the anterior or
posterior portions of the arch. For some patients, this may be an
advantage.
• After crossbite correction is completed, band removal can be difficult
because the teeth are mobile and sensitive. In those patients, sectioning the
bands is appropriate.

128. • An alternative approach is to use a bonded palatal expander.
• Because there is no band fitting, the appliance is easier to place for both the
patient and doctor, and during treatment it is manipulated like any other
RPE appliance.
• Removal of this appliance also can be difficult. It is accomplished with a
band remover engaged under a facial or lingual margin to flex the
appliance and break the bond.
• In addition, the appliance usually needs to be sectioned or portions of the
occlusal plastic removed for a direct purchase on the teeth so the band
remover can effectively lift and separate the plastic from the teeth.

129. • Complete removal of the bonding agent (typically a filled resin that will
adhere to etched tooth surfaces and to the appliance) can be laborious, so
use of only an adequate amount is crucial, but insufficient resin will lead to
excessive leakage onto the nonbonded surfaces, which can result in
decalcification or appliance loss.
• For these reasons, some clinicians use a RMGIC that will bond to both the
plastic appliance and the teeth for retention.
• The strength of the material usually is adequate, and the short-term
fluoride release may be beneficial.

130. • A factor in the decision between a bonded and banded expander is the
vertical effect of maxillary expansion.
• Regardless of the skeletal effect, expansion creates dental interferences as
soon as the posterior teeth begin to move laterally, and the effect is to
rotate the mandible downward and backward.
• Almost always there is a permanent increase in face height after expansion
because of eruption of both maxillary and mandibular posterior teeth
before a solid cusp–fossa relationship of the teeth is established.
• For a patient who had a deep bite as well as a posterior crossbite, this is
good.

131. • For one who had an open bite, this makes the open bite worse.
• In theory, the splint on top of the teeth with a bonded expander would
interfere with eruption of the posterior teeth in both arches, and there is
some (weak) evidence that this is the case in the short term.
• It may be reasonable to use a bonded expander in long-face or open bite
patients who need expansion rather than a banded one.
• For patients with a deep bite, it seems to make no difference in the vertical
effects of expansion which type of expander is used.

132. Treatment of Transverse Mandibular Constriction
• Unlike the maxilla, the mandible has no midline suture.
• It started as two halves, but they fused early in fetal life, and the midline is
solid bone.
• Although removable appliances that look like midpalatal expanders can be
used, they can only move the teeth (and do not do that very well).
• Mandibular transverse expansion was impossible until distraction
osteogenesis became available.
• The first step in distraction, of course, is to cut through the bone; then it
is possible to manipulate the healing callus and generate new bone

133. • There still is a limitation: The expansion is much greater anteriorly than
in the molar region, and the condyles rotate slightly but do not move
laterally.
• Fortunately, this amount of condylar rotation is tolerated without creating
any problems.

134. C) The maxillary arch was expanded at the rate of 1 mm per day with a
banded jackscrew device. At the time of the photo the expansion was
complete and was being retained (note the wire ligature to prevent
further movement of the jackscrew).
(D) and (E) The screw-retained expander for mandibular symphysis distraction osteogenesis, after
removal of the lone incisor, immediately after cuts through the cortical bone. Expansion at the rate of 1
mm per day was done after a 7-day latency period.

135. (F) and (G) The
expander was stabilized
when the desired
expansion had been
obtained and left in
place for 4 months for
maturation and
remodeling of the new
bone.
(H) Nearly 1 year later, with orthodontic
alignment of both arches completed and a
temporary retainer in place
(I) OPG at the time
distractor was
removed. Note the
fill in mature bone in
the distraction area.
Symphysis
distraction is the
only way to deal with
problems created by
missing areas of the
anterior madible

136. Restriction of Excessive Transverse Growth
• Restriction of transverse growth in both jaws is exceptionally difficult,
almost impossible.
• In the maxillary arch a transpalatal lingual arch during the preadolescent
period would maintain molar width but does not affect skeletal growth or
arch width across the premolars and canines.
• In the mandibular arch the length of a lingual arch makes it flexible
enough that some increase in intermolar width probably would occur
despite its presence, and there would be the same lack of effect on both jaw
width and the other teeth.

137. • The major problem this creates is posterior crossbite in a patient with
normal maxillary arch width and very large mandibular arch width.
Patients of that type usually have a wide tongue.
• Even heroic efforts to decrease the mandibular intermolar width (for
instance, wearing an elastic across the arch, running it over the top of the
tongue), rarely succeed, and immediate relapse is likely.
• That leaves the orthodontist with two options: expand the maxillary arch
to match the wide lower arch, or tolerate the crossbite.
• As we have illustrated earlier, sutural expansion increases maxillary width
more anteriorly than posteriorly, just the reverse of what is needed to
match a ,mandibular arch that widens posteriorly, and dental expansion
risks fenestration of the molar roots.

138. • Patients with posterior crossbite have a problem only when it forces a
mandibular shift on closure, and without that, there are neither functional
nor esthetic reasons for correcting it.
• A segmental maxillary osteotomy can provide more expansion posteriorly
than anteriorly.
• That simply is not indicated for a condition that really is not a problem for
the patient.
• The best option: Take that type of posterior crossbite off the problem list
and tolerate it.

139. Conclusion
• Transverse discrepancy in the words of McNamara is quite “Pervasive”.
We need to incorporate routine assessment of transverse dimension in the
clinical examination as opposed to investigating a crossbite. Early
interception of functional shift has been shown as the most effective
intervention in managing a transverse discrepancy. This should be
inculcated in our practice. The use of CBCT in the diagnosis of
Transverse discrepancy and use of RME & its variants should be
practiced on the basis of available best evidence.