Orthognathic Flashcards
What is orthognathic treatment?
when the malocclusion is so severe that orthodontics alone cannot provide a solution
Under which circumstances are orthognathic treatment used?
Severe class 2 skeletal pattern severe class 3 skeletal pattern assymetry vertical problem
Which skeletal relationships can orthognathic treatment correct?
anterior-posterior
vertical
transverse
genioplasty
How can anterior posterior relationships be treated?
the mandible can be moved forwards or backwards
the maxilla can be moved forwards but not backwards
How can the mandible be move forwards?
saggital split osteotomy sub sigmoid (only for small advanacements)
When are vertical corrections needed?
long faces maybe assciated with an AOB
short faces: deep/traumatic overbite
How can short vertical relationships be corrected surgically using the maxilla?
maxilla can be intruded but less predictably extruded
How can vertical relationships be corrected surgically using the mandible?
the mandible can be moved up or down anteriorly but downward movement of the gonial angle is less succesful
How can long vertical relationships be treated with the maxilla?
the maxilla can be intruded
How does intrusion of the maxilla affect the mandible?
the mandible can rotate upwards and forwards and reduce the anterior face height
How can short vertical dimensions be treated with surgery?
since extrusion of the maxilla is not predictable this is most commonly treated with mandibular ramus surgery which results in the mandible being advanced
how can transverse relationships be treated?
expand the maxilla
How does distraction osteogenesis work?
callus is induced in bone and then the proximal and distal ends are distracted and allowed to heal in their new position
What is the clinical technique behind an distraction osteogenesis?
osteotomy apply distracting device activate over five days distract at a rate of 1mm/day fixation maintained for 8 weeks consolidate
How stable is distraction osteogenesis?
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
What are the stages to orthognathic surgery?
planning: lateral ceph presurgical ortho surgery post surgery ortho orthodontic retention
how long does the pre surgery ortho last?
15-18months
how long does the surgery laste?
2-4 hours and in hospotal for 1-3 days post op
how long do you need to take off work?
2-3 weeks
how long is the post-op ortho?
2-8months
What are the complications following orthognathic surgery?
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
What is done in the pre surgery ortho?
- Arch alignment
- Normal inclination of upper and lower labial segment
- Arch width co ordination
What are the aims of Orthognathic surgery?
Function
Aesthetics
Stability
Minimal treatment time
What is the normal intercanthal width?
32 +/- 3mm
What is the normal inter pupillary distance?
65 +/- 3mm
What should be equal to the intercanthal distance?
The alar base width
The ideal chin is what?
3mm +/- 3 posterior to the line through subnasale and perpendicular to Frankfort plane
What types of sugery are there?
Chin
Mandibular Ramus
Mandibular body
Segmental
What type of segmental procedures are there?
Le fort 1/2/3
What can be done in a genioplasty?
Augment the chin
Move chin vertically
Transverse position can be changed to mask asymmetry
What mandibular ramus surgery are there?
Sagittal split
Sub sigmoid
Inverted L
Why is Sagittal split osteotomy popular?
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
How do you perform a Sagittal split?
Inter oral incision and cut bone
Move bone check occlusion and fix
What are the advantages of a Sagittal spilt?
Quick healing Advance or set back Rigid fixation can be used can maintain angle of mandible Major MOM retain in normal position
When would you perform a vertical sub sigmoid osteotomy?
For set back and asymmetry
What are the contra indications to mandibular set back?
Large set backs
Large advancements
