PFM

Question 1

Goal?

Answer 1

Enhance forward displacement of Mx via sutural growth by a combination of Sk. and dental mvm

Question 2

Indication?

Answer 2

• Mx retrusion
• Hypodivergent
• Little to no DAC
• CRMI slide present

Question 3

What is Mx retrusion?

Answer 3

Inadequate length of Mx base

Question 4

How are asians like?

Answer 4

Masaki, 1980:

• sig. shorter anterior cranial base
• obtuse gonial angle
• increased LAFH

Question 5

Addition to make PFM more efficient

Answer 5

Active chin-cup for Pt with combination of Mx retrusion and prognathic Mn

Question 6

Effects?

Answer 6

1) Forward Mx
2) Downward, backward Mn
3) Procline Ui
4) Retro Li

Question 7

How much Mx movement?

Answer 7

Ngan and Moon, 2015
2-4mm forward
-reduced with age

Question 8

Effects of expansion-constriction protocol

Answer 8

Liou, 2005
Forward Mx
Increase upper airway vol.

Question 9

Cases unfavourable for PFM

Answer 9

• Long Mn ramus
• Acute cranial base angle
• Steep Mn angle

Question 10

Instructions of PFM

Answer 10

300-500g/side
30-45 deg forward, downwards from canine region
Distal to U2
10-12hrs/day
3-6 months

Question 11

Bone vs tooth anchored

Answer 11

Same: Mn sagittal changes

Bone:

• greater Mx adv than RME+FM
• better vert. control
• No CW rotation of Mn
• No retro Li

Tooth:

• posterior anchorage loss
• proclined Ui

Question 12

Bone anchored more Mx adv than RME+FM

Who said that

Answer 12

Cervidanes et al. 2010

Question 13

Cochrane evidence

Answer 13

Watkinson, 2013

• only FM recommended
• reduce ANB by 3.93 after 1 yr

Question 14

Evidence for retention

Answer 14

Ngan et al. 1997-1998

Hagg et al. 2003

Question 15

What was the retention study

Answer 15

• 30 Chinese
• RME+FM
• Mixed dentition

Question 16

Results of retention study

Answer 16

4yr follow up: 70% +ve OJ

8yr follow up: 2/3 +ve OJ
1/3 OGS due to unfavourable growth pattern
Sagittal plane and DAC same

Relapse group:

• Mn outgrow Mx by 4x (vs stable grp 2x)
• Mn angle open more
• increased LFH