OGS

Question 1

SARPE stability + evidence

Answer 1

Chamberlain & Proffit, 2011

• sk. expansion with SARPE less than 50% of jackscrew expansion at earlier ages
• sig. dental relapse
• assumed greater transverse stability with SARPE + LF1 not a good reason to avoid segmental

Question 2

When is SARPE indicated

Answer 2

• late adolescent and adults

- when transverse expansion is the ONLY thing pt needs

Question 3

Cl. III sx stability: Mx adv only

Answer 3

80% chance of no. sig. change (<2mm)
NO chance of sig. change
Proffit & White, 2015

Question 4

Cl. II sx stability: Md adv

Answer 4

1st yr post op:
<5%: > 4mm relapse from chin point
20%: >2mm
20%: >2mm adv

Most stable: downward rotation of chin to increase face ht + Mn adv

Least stable: ACW rotation to reduce face ht in long face pt

Question 5

Cl. III v Cl. II

Answer 5

Cl. III more stable after 1 yr post op

- both 80% of <2mm change at 5yr post op

Question 6

Age and Cl. II sx stability

Answer 6

Those tx when bone complete more likely to have backward mvm of chin than those with earlier op
- OJ no diff due to Li proclination

Proffit et al., 2010

Question 7

Mx impaction stability

Answer 7

1st post-op: quite stable
5yrs post-op: 20% >2mm increase in face height due to vert. growth

• amt of relapse not related to amt of impaction
  (Proffit and White, 2015)

Question 8

Mx imp vs TAD intrusion for AOB case

Answer 8

In mild AOB (<6mm) correction. Stability 1-2 yrs post-intrusion = LF1 impaction.

Scheffler et al., 2014

Question 9

Considerations for Cl. III camou

Answer 9

• retraction of Li increase chin prominence(worsen profile)
• L1 exo may not lead to Boltons
• TAD on Mn ramus able to retract entire Mn arch but need L8s or even 7s exo

Question 10

Considerations for Cl. II camou

Answer 10

• avoid over-retraction of Ui -> obtuse NLA -> unaesthetic

- KIV genio to adv and mask proclined Li

Question 11

Preop ortho goal

Answer 11

100% decomp or more

• to acct for dental relapse
• intrude over-erupted incisors for AOB cases
• avoid extruding teeth during levelling for pt going for impaction: increase incisal show/ relapse -> bite opening
• Short face deep bite pt: to level or not -> depend on desired post op ant face ht
• Mx/Mn arch form compatibilty -> avoid canine interference

Question 12

Purpose of post-op intermx elastics

Answer 12

• guiding elastic

- to preventing slide jaw from initial contact to acquired positiong -> difficult to eliminate

Question 13

Retention for surgical Mx expansion with segmental

Answer 13

• immediate VFR

- Hawley FT at least 8months post + PT another 4-6mth

Question 14

Magnitude of OGS movement

Answer 14

Mx adv: 6mm
Mx impaction: dependent on incisor display
Mx downward: short-term stability issue instead, rotate down anteriorly to increase Ui display

Mn setback: unstable
Mn ACW rotation: increase ramal ht, reduce Mn plane angle -> relapse to into AOB due to lack of muscle adaptation
Mn CW rotation: increase AFH and Mn angle quite stable

Question 15

When is camou more likely + evidence

Answer 15

• Average or short facial pattern
• Mild anteroposterior jaw discrepancy
• Crowding less than 4 to 6 mm
• Normal soft tissue features (nose, lips, chin)
• No transverse skeletal problem
  Proffit et al., 2007

Question 16

When is camou less likely

Answer 16

Long vertical facial pattern
Moderate or severe anteroposterior jaw discrepancy
Crowding greater than 4 to 6 mm
Exaggerated features
Transverse skeletal component of problem
(Proffit et al., 2019)

Question 17

Envelope of discrepency

Answer 17

7-2-2-4

3-2-5-4

Question 18

Hierarchy of surgical stability + evidence

Answer 18

Most (Very) stable:

• Mx impaction
• Genio
• Mn forward (short to normal face height)

Middle (Stable):

• Mx adv
• Mx/Mn asymmetry
• Combinations

Worse (Least) stable:

• Mx downgraft
• Mn setback
• Mx expansion

Proffit et al. 2019

Question 19

Factors influencing stability

Answer 19

1) Neuromuscular adaptation
2) Stretch of the pterygomandibular sling -> unstable
3) When soft tissue is relaxed not stretched eg palatal tissues in Mx expansion
4) Change in inclination of Mn ramus -> unstable, condylar sagging