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Orthodontics > Orthognathic > Flashcards

Orthognathic Flashcards

1
Q

What is orthognathic treatment?

A

when the malocclusion is so severe that orthodontics alone cannot provide a solution

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2
Q

Under which circumstances are orthognathic treatment used?

A 
Severe class 2 skeletal pattern
severe class 3 skeletal pattern
assymetry
vertical problem
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3
Q

Which skeletal relationships can orthognathic treatment correct?

A

anterior-posterior
vertical
transverse
genioplasty

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4
Q

How can anterior posterior relationships be treated?

A

the mandible can be moved forwards or backwards

the maxilla can be moved forwards but not backwards

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5
Q

How can the mandible be move forwards?

A 
saggital split osteotomy
sub sigmoid (only for small advanacements)
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6
Q

When are vertical corrections needed?

A

long faces maybe assciated with an AOB

short faces: deep/traumatic overbite

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7
Q

How can short vertical relationships be corrected surgically using the maxilla?

A

maxilla can be intruded but less predictably extruded

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8
Q

How can vertical relationships be corrected surgically using the mandible?

A

the mandible can be moved up or down anteriorly but downward movement of the gonial angle is less succesful

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9
Q

How can long vertical relationships be treated with the maxilla?

A

the maxilla can be intruded

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10
Q

How does intrusion of the maxilla affect the mandible?

A

the mandible can rotate upwards and forwards and reduce the anterior face height

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11
Q

How can short vertical dimensions be treated with surgery?

A

since extrusion of the maxilla is not predictable this is most commonly treated with mandibular ramus surgery which results in the mandible being advanced

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12
Q

how can transverse relationships be treated?

A

expand the maxilla

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13
Q

How does distraction osteogenesis work?

A

callus is induced in bone and then the proximal and distal ends are distracted and allowed to heal in their new position

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14
Q

What is the clinical technique behind an distraction osteogenesis?

A 
osteotomy
apply distracting device
activate over five days
distract at a rate of 1mm/day
fixation maintained for 8 weeks
consolidate
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15
Q

How stable is distraction osteogenesis?

A

movement of the maxilla more than 5-6mm is more susceptible to relapse

moevement of the mandible by more than 8mm is more susceptible to relapse

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16
Q

What are the stages to orthognathic surgery?

A 
planning: lateral ceph 
presurgical ortho
surgery
post surgery ortho
orthodontic retention
17
Q

how long does the pre surgery ortho last?

A

15-18months

18
Q

how long does the surgery laste?

A

2-4 hours and in hospotal for 1-3 days post op

19
Q

how long do you need to take off work?

A

2-3 weeks

20
Q

how long is the post-op ortho?

A

2-8months

21
Q

What are the complications following orthognathic surgery?

A 
bleeding
infection
loss of sensation
screw head dehiscence
faiulre to get full correction
relapse
codylar head problems/condylar sag
Growth disturbances
TMJ heamoarthrosis or oedema
Unfavourable split or fracture
Extrusion of teeth
Perio defects 
TMJ dysfunction
22
Q

What is done in the pre surgery ortho?

A
  1. Arch alignment
  2. Normal inclination of upper and lower labial segment
  3. Arch width co ordination
23
Q

What are the aims of Orthognathic surgery?

A

Function
Aesthetics
Stability
Minimal treatment time

24
Q

What is the normal intercanthal width?

A

32 +/- 3mm

25
Q

What is the normal inter pupillary distance?

A

65 +/- 3mm

26
Q

What should be equal to the intercanthal distance?

A

The alar base width

27
Q

The ideal chin is what?

A

3mm +/- 3 posterior to the line through subnasale and perpendicular to Frankfort plane

28
Q

What types of sugery are there?

A

Chin
Mandibular Ramus
Mandibular body
Segmental

29
Q

What type of segmental procedures are there?

A

Le fort 1/2/3

30
Q

What can be done in a genioplasty?

A

Augment the chin
Move chin vertically
Transverse position can be changed to mask asymmetry

31
Q

What mandibular ramus surgery are there?

A

Sagittal split
Sub sigmoid
Inverted L

32
Q

Why is Sagittal split osteotomy popular?

A

It is the commoner type used for mandibular advance and set back because there is ridged fixation which means it wil be stable and predictable

Rapid surgery and safe recovery

33
Q

How do you perform a Sagittal split?

A

Inter oral incision and cut bone

Move bone check occlusion and fix

34
Q

What are the advantages of a Sagittal spilt?

A 
Quick healing
Advance or set back 
Rigid fixation can be used
can maintain angle of mandible 
Major MOM retain in normal position
35
Q

When would you perform a vertical sub sigmoid osteotomy?

A

For set back and asymmetry

36
Q

What are the contra indications to mandibular set back?

A

Large set backs

Large advancements

Orthodontics (28 decks)

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