UNIVERSITY OF GLASGOW

MANAGEMENT OF TRANSVERSE DISCREPANCIES

Personal notes

Mohammed Almuzian

1/1/2013

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Table of ContentsTransverse discrepancies, displacements, crossbites & rapid maxillary expansion RME...............4

Crossbites.........................................................................................................................................4

Displacement....................................................................................................................................4

Normal growth and development of the arch form and width.........................................................4

Posterior crossbites...........................................................................................................................5

Prevalence.........................................................................................................................................5

Benefits of treating displacement.....................................................................................................5

Aetiology of posterior crossbites......................................................................................................5

1. Skeletal factors......................................................................................................................5

5. Other causes...........................................................................................................................5

Diagnosis..........................................................................................................................................6

Classification of posterior crossbites................................................................................................6

1. Unilateral Crossbite with Displacement................................................................................6

Clinical features................................................................................................................................6

Treatment options unilateral crossbite with mandibular displacement............................................6

Harrison and Ashby, 2008 Cochrane , Main results:........................................................................6

2. Unilateral crossbite with no mandibular displacement.............................................................7

3. Bilateral Crossbite.....................................................................................................................7

4. Posterior mandibular displacement...........................................................................................7

Maxillary expansion.........................................................................................................................8

Rationale for expansion treatment....................................................................................................8

General indication of the expansion.................................................................................................8

Contra-indications of maxillary expansion......................................................................................8

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Methods of maxillary expansion......................................................................................................9

Types................................................................................................................................................9

Advantages of removable expanders................................................................................................9

Disadvantages of removable expanders...........................................................................................9

Types..............................................................................................................................................10

Design.............................................................................................................................................10

Indications......................................................................................................................................10

Advantages.....................................................................................................................................11

Disadvantages.................................................................................................................................11

Clinical Management......................................................................................................................11

Indications of RME........................................................................................................................13

Contraindications of RME..............................................................................................................14

The effects of RME........................................................................................................................14

Side effects of the RME.................................................................................................................15

The influence of height of RME.....................................................................................................16

Activation schedule for RME.........................................................................................................16

1. Timms..............................................................................................................................16

2. Isaacson............................................................................................................................16

Slow maxillary expansion steps.....................................................................................................17

Appliances have been used for rapid and slow maxillary expansion:............................................17

1. Removable appliances (discussed before).......................................................................17

2. Fixed Appliances.............................................................................................................17

Tooth borne......................................................................................................................17

Tooth and tissue borne ( Banded, Bonded like Cast Cap Splints or Acrylic Splints).....17

Fixed expander appliances.............................................................................................................17

1. Tooth - tissue borne appliances...........................................................................................17

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2. Tooth borne appliances Include:.........................................................................................18

Bonded R.M.E................................................................................................................................18

Technique.......................................................................................................................................19

Indications......................................................................................................................................19

Evidence.........................................................................................................................................19

Problems.........................................................................................................................................19

Factors & Yardsticks that determines the type and technique of expansion..................................20

Stability and retention.....................................................................................................................20

Treatment of scissor bite................................................................................................................21

Appliances for unilateral maxillary expansion...............................................................................21

Anterior crossbites..........................................................................................................................22

Prevelance.......................................................................................................................................22

Treatment of anterior crossbites.....................................................................................................22

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Transverse discrepancies, displacements, crossbites & rapid maxillary expansion RME

CrossbitesThe British standard Glossary of Dental Terms defines crossbite as follows:

A transverse discrepancy in tooth relationship.

In a buccal crossbite, the lower arch is wider than the upper so that the buccal cusps of the lower occlude lateral to the buccal cusps of the upper teeth.

Where the lower buccal teeth occlude lingually to the upper buccal teeth there is a lingual crossbite or scissor bite.

A crossbite may be unilateral or bilateral and may involve varying numbers of teeth.

If the transverse relationship is cusp-cusp then it is termed cross bite tendency.

Also used to describe reverse overjet of one or more incisor teeth.

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.

Normal growth and development of the arch form and widthArch dimensions change with growth. It is therefore necessary to distinguish changes induced by appliance therapy from those that occur from natural growth. The total growth between 4 and 17 years amounts to ~7mm. Bjork & Skieller 1974. The average changes achieved in a sample reported by Moyers et al 1976:

1. Growth at the mid-palatal suture is the largest contributor to increase in maxillary width, and this is normally complete by age 17.

2. Between the ages of 7 and 12 years of age, the male have more growth than female and there is more growth in the upper (approximately 3 mm) than the lower arch (approximately 2 mm).

3. After the age of 12, little growth in arch width is seen only in males while the female show constriction especially at intercanine area.

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Posterior crossbites

Prevalence 1. Affects 8-16% of population (Foster & Hamilton 1969)

2. No difference between gender and race.

3. 16-50% self-correcting (Petren 2003).

4. 80% associated with mandibular displacement

Benefits of treating displacement 5. Aesthetic benefits by widening the buccal corridor6. Psychological benefits 7. Creation of space to relief crowding8. Eliminate the undesirable growth modification effects of the displacement which can result in

true mandibular asymmetry (Pinto et al 1991).9. Avoid TMD in susceptible patient (weak evidence)10. Avoid exacerbation of plaque related Pd damage 11. Avoid tooth surface loss

Aetiology of posterior crossbites

1. Skeletal factors Due purely to a mismatch in the relative widths of the arches,

To an anterior-posterior discrepancy resulting in relative cross bite.

True skeletal asymmetry (hemimandibular elongation…….)

2. Dental factors3. Soft tissue factors

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 and.

4. Habits: prolonged sucking habits.

5. Other causes1. Congenital causes: cleft lip and palate,

2. Trauma

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3. Pathology of the TMJ’s

Diagnosis 1. EOE

2. IOE

3. Ceph, PA, CBCT

4. SM

5. EMG

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 unilateral crossbite with mandibular displacement 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)

Harrison and Ashby, 2008 Cochrane , Main results: Using the search strategy seven randomised and five controlled clinical trials were identified but following correspondence with the authors, three of the randomised and one of the controlled clinical trials were reclassified giving five randomised and seven controlled clinical trials for inclusion in the review. For the update an additional CCT was found giving five RCTs and eight CCTs for inclusion in this update.Trials comparing occlusal grinding in the primary dentition with/without an upper removable

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expansion appliance in the mixed dentition versus no treatment, banded versus bonded and two point versus four point rapid maxillary expansion, banded versus bonded slow maxillary expansion, transpalatal arch with/without buccal root torque, an upper removable expansion appliance versus quad-helix were identified.Occlusal grinding in the primary dentition with/without the addition of an upper removable expansion plate, in the mixed dentition for those children who did not respond to grinding, was shown to be effective in preventing a posterior crossbite in the primary dentition from being perpetuated to the mixed and permanent dentitions.No evidence of a difference in treatment effect (molar and canine expansion) between the test and control intervention was found in the trials which compared banded versus bonded and two point versus four point rapid maxillary expansion, banded versus bonded slow maxillary expansion, transpalatal arch with/without buccal root torque, or upper removable expansion appliance versus quad-helix. Insufficient data were provided in the paper comparing two point versus four point rapid maxillary expansion to allow a formal analysis.

Authors' conclusions: 

The evidence from the trials reported by Thilander 1984 and Lindner 1989 suggests that removal of premature contacts of the baby teeth is effective in preventing a posterior crossbite from being perpetuated to the mixed dentition and adult teeth. When grinding alone is not effective, using an upper removable expansion plate to expand the top teeth will decrease the risk of a posterior crossbite from being perpetuated to the permanent dentition.

2. Unilateral crossbite with no mandibular displacementA. Usually due to underlying skeletal asymmetry eg unilateral cleft, unilat. Condylar

hyperplasia

B. Correction is seldom indicated

C. Surgery for severe cases is indicated

3. Bilateral CrossbiteA. Usually associated with a skeletal discrepancy in transverse, AP or both

B. Usually there is no displacement & no functional indication for treatment

C. Best treated with RME but you do get a lot of relapse overcorrect

D. Care should be taken to avoid the development of iatrogenic unilateral cross bite with displacement post expansion.

4. Posterior mandibular displacementThis associated with CLII D2 and better to be treated ASAP to avoid TMJ problem

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Maxillary expansion

Rationale for expansion treatmentThe aim of maxillary expansion treatment is to increase the distance between to 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.

3. 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.

General indication of the expansion1. Unilateral crossbite with displacement– Harrsion and Ashby 2001

2. Interceptive treatment of an ectopic canine (Armi & Baccetti, 2011, Bacceti 2011)

3. To provide space in mild-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

Contra-indications of maxillary expansion1. Uncooperative patient

2. In a periodontally weak dentition.

3. Severly buccally tipped teeth

4. High angle & reduced overbite

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5. Convex profile

6. True skeletal asymmetry, Bishara 2001

7. Large amount of expansion required

Methods of maxillary expansion

I. Removable appliances

Types 1. URA with a midline expansion screw (Jack screws)

A. Good retention is necessary

B. URA with midpalatal screw, success rates is 50%

C. Asymmetric expansion may be produced by sectioning the baseplate so that more teeth are in contact with it on the non-expansion side.

D. The mode of action is

Predominantly buccal tipping of the molar teeth.

A small amount of separation of the midpalatal suture is possible, especially in prepubertal children, but this is unpredictable. Skieller 1964.

2. URA with Coffin springs a

A. Walter Coffin in 1877 introduced a spring called Coffin spring.

B. Coffin springs provide a continuous, as opposed to interrupted orthodontic force (with a URA)

C. It is less well tolerated and retained

Advantages of removable expanders They can easily incorporate other active components such as springs,

Can be part of a functional appliance such as a twin block.

Disadvantages of removable expanders They rely on patient compliance

Produce mainly dental changes.

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As buccal tipping of the molars occurs, the palatal cusps tend to drop down and this can cause overbite reduction and increase of MMPA.

II. Functional appliances1. Active expansion (usually with either expansion screw or palatal arch) to prevent crossbite formation whilst a C11 molar relationship is being obtained

2. Passive expansion: Frankel appliance produces passive expansion only by removing influence of buccal tissues with buccal shields

III. Quadhelix and the fixed W palatal expander

It is a useful intermediate upper arch expansion device and has been extensively described and popularised by Ricketts (1979).

TypesA. Custom made: 1-0·9mm stainless steel with four helices to increase flexibilityB. Preformed ready type A removable or fixed quadhelix constructed of Blue Elgiloy for increased flexibility/

adjustability and an Elgiloy based system called ORTHORAMA 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

Design The quadhelix is a fixed appliance retained by bands

cemented on the permanent first molars. It consists of a w-shaped 1mm spring, usually stainless steel,

incorporating 4 helices to add flexibility and increase range of action. The quad helix consists of a pair of anterior helices and a pair

of posterior helices. The portion of wire between the two anterior helices is

called the anterior bridge. The wire between the anterior and posterior helices is called the palatal bridge. The free wire ends adjacent to the posterior helices are called outer arms.

Indications 1. Intermediate upper arch expansion 2. Bi-helix used in mandibular arch in grossly narrowed or distorted arches, or to aid

correction of severe scissors bite

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3. Expand the upper arch anteroposteriorly when its arm length increased

4. Provide access and space with cleft palate before bone grafting

5. Used with facemask same as RME

6. Molar derotation7. Habit breaking effects8. Method of attachment to align impacted teeth or to perform certain teeth movement9. Provide anchorage (AP and transverse)

Advantages 1. Reduced need for patient compliance because it is fixed

2. Efficiency and evidences:

The quadhelix produces a combination of buccal tipping and skeletal expansion, typically in the ratio of 6:1. (Frank 1982)

Quad. (QH and RME success rates is 100%, Harrison and Ashly 2008 Cochrane review)

Quadhelix versus buccal arch expansion — no difference in expansion achieved and buccal arch cheaper McNally 2003

Herold (1989) compares the use of RME, a quadhelix and a removal appliance, and came to the conclusion that no method of expansion was substantially better than the other.

Disadvantages 1. The limited amount of skeletal change,

2. Opening of the bite due to molar buccal tipping.

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.

Sometimes, the appliance can leave an imprint on the tongue; however, this will rapidly disappear following treatment.

Expansion should be continued until the palatal cusps of the upper molars meet edge-to-edge with the buccal cusps of the mandibular molars.

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Expansion can be done intraorally using the triple peak plier.

Retention after the expansion

A. At least three-month retention period before it is removed

B. Achieved expansion should be retained with an upper removable appliance.

C. If fixed appliances are being used, the quadhelix can be removed once stainless steel wires are in place.

IV. Rapid maxillary expansion (RME)

History Angell 1860 is considered the father of rapid maxillary expansion.

Hass during the 1950's reintroduced rapid maxillary expansion

Applied anatomy related to RME The maxilla together with the palatine bone forms the hard palate, floor and greater part of

the lateral walls of the nasal cavity.

The maxilla is a paired bone that articulates with its opposite member and various other bones including frontal, ethmoid, nasal, lacrimal, vomer, zygomatic and the palatine bones.

The inter-maxillary and the inter-palatine sutures are collectively called the mid-palatal suture.

The sphenoid and the zygomatic bones have a buttressing effect resisting mid - palatal suture opening posteriorly.

Mechanism of RME1. It mainly used if the post teeth are buccally inclined then RME.

2. This is best carried out prior to or during the pubertal growth spurt (Baccetti 2001), as after this time the suture becomes more heavily interlocked which may impede separation. Melsen 1975, Some say can use on patients > 15yrs

3. 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.

4. Clinical tips: Bishara 1998

A. Postpone extraction of first premolars until palatal expansion is completed because these teeth together with the first molars are often used as abutment teeth for anchoring the appliance.

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B. Avoid orthodontic movement of the maxillary posterior teeth prior to RME since Mobile teeth may tip faster during expansion.

C. Position the screw as superiorly as possible in the palatal vault.D. Start turning the jackscrew 15 to 30 minutes after the appliance is inserted to allow sufficient

setting time for the cementing mediumE. 2turns daily → 0.5mmF. Creates 10-20IIb pressure across the suture

G. Microfractures of interdigitating bone spicules. Monitor the midpalatal suture with weekly maxillary occlusal films. The suture will open within 7 to 10 days in most patients. If the suture does not split within 2 weeks, the lack of skeletal response may result in tipping of the teeth and possible fracture of the alveolar plates.

H. Suture opens wider and faster anteriorly because of buttress effect of distally placed zygomaticomaxillary sutures

I. The separation of the suture can also be visualised radiographically.

J. Transient side effect: patient will experience dizziness, pain and discomfort so it is better to warn him

K. Midline diastema opens

L. Central diastema then begins to close as a result of some skeletal relapse and stretch of the transeptal fiber that caused some reciprocal incisors movement

M. After the expansion is completed and the screw is immobilized for 3 to 6 months and place a palatal holding arch between the maxillary first molars to minimize relapse tendencies.

N. There appears to be no difference in the amount of expansion of the back teeth obtained when using a banded or bonded rapid maxillary expansion brace. Harrison and Ashby, Cochrane 2008.

O. During the orthodontic treatment phase, incorporate some expansion in the maxillary arch wire.P. In a patient with a severely constricted palate, the clinician might consider some of the following

options: Initiate expansion as early as possible, Expand the palate in two phases, For patients with narrow palates, clinicians may choose

a telescopic screw, an interchangeable screw, or construct two appliances with progressively larger screws. Overexpand the maxillary arch, Prolong the period of fixed retention, Consider extraction of teeth in one or both jaws to facilitate constriction of the dental

arches,

Indications of RME1. Interceptive treatment of an ectopic canine (Armi & Baccetti, 2011, Bacceti 2011)

2. To provide space in mild-moderate crowding 1mm of arch expansion in the molar region gives ~0.6mm of space for relief of crowding (O’Higgins & Lee, 2000). So 3mm of expansion would allow relief of ~2mm of crowding without changing the inclination of the labial segments.

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3. Buccal inclined molars since RME produce more bodily movement (Herold, 1988)

4. Adjunctive with reverse facial mask treatment to disrupt the suture and to correct the transverse discrepancy if present (Kim 1993). Vaughn 2005 disagree with that.

5. Unilateral crossbite with displacement– Harrsion and Ashby 2001

6. V shaped arch in a 'thumb-sucker' specially if skeletal expansion more than 4mm is required

7. Child with < 31mm of intermolar width at age 7yrs is unlikely to attain adequate arch dimensions through normal growth alone

8. Combined orthodontic surgical cases for arch coordination (usually SARPE)

9. Pre-bone graft in CLP patients

Contraindications of RME1. Uncooperative patient

2. Adult patient

3. High angle & reduced overbite

4. Convex profile

5. Severely buccally tipped teeth

6. In a periodontally weak dentition.

7. True skeletal asymmetry, Bishara 2001

8. Large amount of expansion required

The effects of RME1. Maxillary skeletal effect:

The opening of the mid - palatal suture is fan-shaped or triangular with maximum opening at the incisor region and gradually diminishing towards the posterior part of palate

Similar fan shaped or non-parallel opening is also seen in the superio-inferior direction. The maximum opening is towards the oral cavity with progressively less opening towards the nasal aspect

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2. Effect on alveolar bone: The alveolar bone in the area adjacent to the anchor teeth bends slightly. This is due to the resilient nature of the alveolar bone.

5. Effect on maxillary anterior teeth: midline spacing between the two maxillary central incisors. The incisor separation is about half of the distance the screw is opened. By three to five months, the midline diastema closes as a result of the transseptal fiber traction and skeletal relapse

5. Effect on maxillary posterior teeth: These teeth show buccal tipping and are also believed to extrude to a limited extent.

6. Effect on mandible: Most authors have observed a downward and backward rotation of the mandible following rapid expansion.

6. Effect on adjacent cranial bones and sutures: Rapid maxillary expansion not only results in opening of the mid - palatal suture but also has far reaching effects on adjacent cranial

7. Effects of R.M.E. on nasal cavity: Following rapid maxillary expansion an increase in intranasal space occurs due to the outer walls of nasal cavity moving apart. This increase in nasal cavity width is maximum in the inferior region of the nasal cavity and gradually decreases towards the superior aspect. Similar gradient is also found in an anterio-posterior direction with the greatest increase being in the anterior region.

8. Air flow resistance is believed to reduce by 45 - 60 %, thereby improving nasal breathing.

Side effects of the RME1. Transient complications:

Pain & discomfort

Patient will experience dizziness,

Temporary diplopia

Pressure necrosis of palatal mucosa

Inability to activate appliance

2. Elongation of the face by

Downward and forward maxillary movement,

Backward rotation of the mandible

3. Buccal molar tipping and extrusion,

4. Controversial evidence: periodontal breakdown compares with just using URA or FA

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5. Effects on the nose including widening of alar base width and reduced resistance to nasal air flow. The magnitude of these changes varies and may be age-related. Cross & McDonald 2001

6. Expansion of the mandibular arch also occurs as a response to RME. McNamara 1999

The influence of height of RME Marquis 2012 through an infinite element study showed

1. Close to the palate:

There were extrusive tendencies when the screw was simulated above the centre of resistance of the teeth and nearer to the palate.

There were distal displacements when the screw was simulated close to the palate

2. Away from the palate:

Greater amounts of buccal crown tipping were registered when the hyrax screw was far away from the palate.

There were mesial displacement tendencies when the screw was simulated far away from the palate.

Activation schedule for RME

1. Timms For patients of up to 15 years of age, one turn rotation in the morning and evening.

In patients over 15 years, Timms recommends half turn activation 4 times a day.

2. Isaacson In young growing patients, they recommend two turns each day for 4 - 5 days and later one turn

per day till the desired expansion is achieved.

In case of non-growing adult patients, they recommend two turns each day for first two days, one turn per day for the next 5- 7 days and one turn every alternate day till desired expansion is achieved.

V. Slow maxillary expansion1. Proffit 2000 describes that when RME is used,

2. Separation of the maxillary suture occurs rapidly as can be seen by the rapid development of a midline diastema.

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3. Once sufficient expansion has been obtained, the appliance is left in place to maintain the change.

4. However, during this period the 2 halves of the maxilla tend to move back towards each other, possibly under the influence of tension in the palatal mucoperiosteum.

5. As the appliance is still in place, the expansion is maintained, but compensatory dentoalveolar changes occur in response to the skeletal relapse.

6. The final ratio of skeletal to dentoalveolar change is about 50:50, which is very similar to what is obtained by expanding the maxilla more slowly using the same appliance.

7. In conclusion, Proffit suggests that slow expansion with a rigid appliance produces the same result by a more physiological delivery of forces.

Slow maxillary expansion steps1. Maxillary arch is expanded slowly at a rate of 0.5- 1 mm per week.

2. The forces. 2-4 pounds as against 10-20 pounds generated during rapid maxillary expansion.

3. Take as much as 2-5 months.

4. Slow expansion has traditionally been termed dento-alveolar expansion, although some skeletal changes can be observed.

5. The slower expansion techniques have also been associated with a more physiologic adjustment to the maxillary expansion, producing greater stability and less relapse potential than in rapid expansion procedures.

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Appliances have been used for rapid and slow maxillary expansion:

1. Removable appliances (discussed before)

2. Fixed Appliances

Tooth borne

Tooth and tissue borne ( Banded, Bonded like Cast Cap Splints or Acrylic Splints)

Fixed expander appliances

1. Bone borne

2. Tooth - tissue borne appliances A. Hass type: The first premolar and molar of either side are banded. A thick

stainless steel wire of 1.2 mm diameter is soldered on the buccal and lingual aspects connecting the premolar and molar bands. The lingual wire is kept longer so as to extend past the bands both anteriorly and posteriorly. These extensions are bent palatally to get embedded in the palatal acrylic. The split palatal acrylic has a midline screw. The plate does not extend over the rugae area .

B. Derichsweiler type: similar to Hass appliance but without buccal wire.

3. Tooth borne appliances Include:A. Isaacson type or MINNE expander: This is a tooth borne appliance without

any acrylic palatal covering. This design makes use of a spring loaded screw called a MINNE expander (developed at the University of Minnesota, Dental School) .The first premolars and molars are banded. Metal flanges are soldered onto the bands on the buccal and lingual sides. The expander consists of a coil spring having a nut which can compress the spring. This coil spring is made to extend between the lingual metal flanges that have been soldered. The expander is activated by closing the nut so that the spring gets compressed

B. Hyrax type: This type of appliance makes use of a special type of screw called HYRAX (Hyrake expansion or Hygienic Rapid Expander). The screws have heavy gauge wire extensions that are adapted to follow the palatal contour and are soldered to bands on premolar; and molars.

Bonded R.M.E1. Cast Cap Splints

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2. Acrylic Splints

It is useful when banding is difficult especially in mixed dentition when banding the D or E is complicated. Alternatively, only the permanent first molars can be banded.

Also it is indicated when the tipping to be controlled or when the inclination of the abutment are different which make the insertion of the band difficult

VI. Fixed appliancesExpansion can be obtained during fixed appliance treatment in a variety of ways.

1. The use of overexpanded stainless steel archwires, typically .019x.025 or .021x.025 can produce expansion with reduced buccal tipping as the archwire maintains torque control.

2. Expansion arches are auxiliary wires 1.13mm ss that are placed in the EOT tubes on the molar bands and secured to the main archwire with a ligature anteriorly. They are simple to use but will tend to produce some buccal tipping, which can be counteracted by putting buccal root torque in the main archwire. McNally 2008 found same effect of the auxiliary AW and the Q helix

3. Cross elastics running from the palatal aspect of upper teeth to the buccal aspect of lower teeth can produce some transverse correction. However, there will also be a vertical component of force which will tend to extrude molars, and is contraindicated in high angle / reduced bite patients.

4. Self-ligation appliances: If an archwire with a larger arch form is chosen from the outset of treatment and twinned with a low friction bracket system, significant expansion and change in arch form is possible. However, there is no evidence that this is any more stable than any other method of expansion.

VII. Surgical assisted RME

Technique It is a part of distraction osteogenisis

It involve Lefort I osteotomy with RME

Following SARPE, the maxilla should be allowed to remain stationary for five days prior to initiation of expansion of the maxilla at 0.5mm/day (this allows capillary healing across the osteotomy area- Ilizarov theory of distraction).

It is better to divert the root of the central to allow surgical cut

Indications1. Failed orthodontic expansion

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2. Adult patient

3. Sever maxillary transverse deficiency >5mm

4. Extremely thin, delicate gingival tissue or presence of significant buccal gingival recession in the canine-premolar region in the maxilla

EvidenceSurgical and non-surgical techniques: No significant difference in stability of expansion after 1 yr Berger et al., 1998

Problems1. PD damage at area of osteotomy2. Root damage at area of osteotomy3. Oronasal fistula4. Numbness of lip and palate due to osteotomy side effect5. Risk of nasal septum deviation

Factors & Yardsticks that determines the type and technique of expansion1. Age

2. Aetiology

3. Buccolingual inclination of the post teeth

4. OB

5. Buccal gingivae thickness

6. The clinical condition of the teeth

7. Intermolar width measurement

measure the distance between the most gingival extension of the buccal grooves on the mandibular first molars

measure the distance between the tips of the mesiobuccal cusps of the maxillary first molars; and

subtract the mandibular measurement from the maxillary measurement.

The average differences in persons with normal occlusion are + 1.6 mm for males and + 1.2 mm for females

If:

1. 1-5mm can be treated by URA

2. 5-6mm can be treated with Q-helix

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3. More than 6mm need RME in growing pt and SARPE in adults

4. One should overexpand the molars 2 to 4 mm beyond the required distance to allow for the expected post fixation relapse.

Stability and retention.1. Up to 40% relapse has been found for all three forms of active expansion (Quad-helix, URA

expansion plates, or rapid maxillary expansion), and there is no difference between them, Herold 1989.

2. Little et al., 1990 showed that 89% of expansion in mixed dent relapses.

3. Schiffman 2001 Maxillary expansion: a meta-analysis: only 2.4 mm of expansion remaining after more than a year which was no greater than what has been documented as normal growth. There is insufficient data to conclude that any useful expansion beyond that can be expected through normal growth was retained.

4. A degree of overexpansion is therefore advisable in anticipation of this.

5. Stopping the cause (habit or mouth breathing)

6. Achievement of good buccal segment intercuspation may help to enhance stability of crossbite correction.

7. The method of retention is also important, and less relapse occurs with fixed retainers than with removable. as the rigid acrylic baseplate, removable retainers are used offers more resistance to relapse forces than the more flexible Essix type

8. Mode of respiration. Expansion may be less stable in mouth breathers because of the lower natural tongue position.

9. Favourable AP and transverse growth.

Treatment of scissor bite1. Mild to moderate

A. In a child, a functional appliance can be used to correct this relationship by advancing the mandible forward and by doing so this may help correct the lingual crossbite.

B. In an adult, fixed appliances can be used with cross-elastics and an expanded mandibular archwire, buccal crown torquing of lower posterior, expanded archwire, .

2. Sever A. If there is a skeletal class II base relationship, mandibular advancement surgery may help correct

the lingual crossbite.B. Surgical techniques using distraction osteogenesis for widening the mandibular arch or

constriction of maxillary one have also been described.

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Appliances for unilateral maxillary expansionSome children do have true unilateral crossbites due to unilateral maxillary constriction of the upper arch. In these cases the ideal treatment is to move selected teeth on the constricted side. To a limited extent, this goal can be achieved by using:

1. Different length arms on a W-arch or quad helix but some bilateral expansion must be expected

2. URA with asymmetric sectioning of the acrylic plate and screw3. An alternative is to use a mandibular lingual arch to stabilize the lower teeth and attach

cross elastics to the maxillary teeth that are at fault.4. TAD can be used to hold the unaffected side and allow the conventional expansion

technique to work on the affected side. Kim , 2010

Anterior crossbites

PrevelanceIn permanent dentition, 0.8% Lipton 1996

Treatment of anterior crossbites1. If dental Xbite

A. Bodily movement use fixed appliance 2*4 appliance

B. Simple tipping movement use URA with posterior capping, Z spring, double cantilever spring, crossed cantilever spring, screw plate.

Requirement for successful result of the treatment by URA:

A. Cooperative patient.B. Growth direction and degree.C. Retroclined or uprighted incisorsD. The degree of AP position of the tooth in the crossbiteE. Adequate spaceF. Deep or average OBG. The LLS are aligned. If they need an alignment it is better to delay it after correction of crossbiteH. Condition and position of the opposing tooth/teeth. If lower canine, which oppose the crossbite

upper incisor is big or buccally displaced, it is better to treat it before correction of crossbite or at the same time.

I. Position of the unerupted canine which might cause root resorption of the incisors.

2. Dentoalveolar or mild skeletal then

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A. Chincap

B. Frankle 3 (Functional)

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