Cl.III

Question 1

Prevalence of Cl. III

Answer 1

22. 4% (Soh et al., 2005)
    - Singapore Asian Male
    - Malay and Chinese similar
    - Indian lowest

Question 2

Eitology

Answer 2

Heredity

• Autosomal dominant
• Incomplete penetrance
• Variable expression

Question 3

Benefits of treating Cl. III early

Answer 3

• maximise orthopedic effect
• imp stability
• increase Mx arch perimeter-> more space for eruption of canine and premolars

Question 4

Risk of no early tx

Answer 4

Gingival recession of Mn incisors
Incisor wear
Worsening growth pattern

Question 5

Adv of 2x4

Answer 5

Mx expansion -> improved arch perimeter-> reduce no. of exo in patients with slight to mild crowding
3D control of tooth movement with light force

Question 6

Adv. of MARPE + FM

+ evidence

Answer 6

Moon (2014)

• much great Mx adv than conventional (also as much as Sx)
• possibility in early teenage years
• NO unwated dentoalveolar changes e.g proclination of U1
• NO tipping of post tt
• NO CW rotation of Mn
• High angle pt

Question 7

Effects of Cl. III elastics

Answer 7

• affect inclination of occlusal plane
• interincisal relationship
• TMJ
• downwards backwards rotation of Mn
• procline Ui
• extrude U molars

Question 8

When is 1 lower incisor exo indicated and factors to consider

Answer 8

• anterior crossbite
• edge-to-edge rs
• amt of anterior crowding
• Bolton’s
• degree of -ve OJ/OB

Question 9

Cl. III TAD placement

Answer 9

Retraction of Mn arch:

• retromolar
• btw L5/6
• btw L6/7

Mx protraction:

• buccal and palatal
• more apical
• limit mvm possible

Question 10

Characteristics of Sk. III OGS pt

Answer 10

• short ant. and post. cranial base
• smaller saddle angle
• short mx length but at normal position
• longer mn length
• increased LAFH
• larger gonial angle
• sig. DAC
• retrusive U lip

Question 11

Adv of distraction osteogenesis

Answer 11

1) greater dist. of mvm than OGS only

2) deficient jaws can increase in size at an earlier age

Question 12

Disadv. of DO

Answer 12

• movements not precise:Mx/Mn move forward but unable to place it in planned place
• overcorrection req

Question 13

Relapse of Mx DO evidence

Answer 13

22% after 3 yrs
with external distractor
Aksu, 2010

Question 14

SARPE sx cuts

Answer 14

• lateral corticotomy
• maxillosphenoid jx disarticulated
• septum severed
• lateral nasal wall cut
• midpalatal suture split
• palatal jackscrew to expand mx

2 separate surgeries req.

Question 15

SARPE v MARPE

Answer 15

MARPE: more force, less rapid
- expansion more parallell from front view

SARPE:

• force loading at the molars -> more expansion at lower part of Mx -> CW rotation of Mn-> bite opening
• not suitable for high angle cases