S2 -Facial deformity and orthognathic surgery Flashcards
What is orthognathic surgery
- surgery to treat facial disproportion i.e. correct dentofacial deformity jaw & facial bones
- underdeveloped/overdeveloped/deformed
- sub-specialty of OMFS
- multi-disciplinary team: ortho, OMFS, dentistry, psychology accurate dx and tx planning is essential
Proportion of the face
Which type of radiograph is used for analyse/assess patient’s facial proportions
lat ceph
Lat ceph landmarks
What do different lines/planes/angles help us determine
facial proportions and where disproportion might be e.g. which jaw is at fault
Indications of orthognathic surgery
- difficulty chewing or biting food
- difficulty swallowing
- TMD & headache
- excessive occlusal wear
- open bite
- unbalanced facial appearance*
- facial injury or congenital defects
- receding chin
- mandibular prognathism
- incompetent lips
- chronic mouth breathing & dry mouth
- obstructive sleep apnoea
*mainly difficulty in accepting facial appearance, psychology needs to be assessed first
What characteristics are open bite usually associated with. How to correct orthognatically?
long face, posterior part of maxilla is too well developed
vertical maxillary excess is reduced by lifting mx up and auto-rotation of md back into different occlusion
Orthognathic tx for prognathic and retrognathic mandible
prognathic - push back md to rebalance face
retrognathic - bring md forward
Treatment goals of orthognathic surgery
- establish better function
- improve dental occlusion
- normalise/optimise facial aesthetics
- improve overall patient health
Surgical approaches for orthognathic surgery
- Le Fort 1 maxillary osteotomy (to move maxilla)
- Bilateral sagittal split osteotomy (splitting B/L ramus of md)
- Bimaxillary surgery (balance movement in both jaws, most pts have both jaws moved)
- Genioplasty (chin)
- Segmental Osteotomies (mainly for chinese patients due to complexity of width and A-P discrepancy)
What has been done
le fort 1 maxillary osteotomy
bilateral sagittal split osteotomy
genioplasty
What are the fundamental surgical principles of orthognathic surgery
Osteotomy & Fixation
Osteotomy - to seperate mx/md from skull and/or TMJ articulation and then fix bone segment to new planned position
Fixation - achieved by Titanium miniplates and screws or IMF to allow stabilisation for bone healing
Pre-surgical orthodontics & Post-surgical orthodontics (very important)
How long does the process take?
Pre-surgical ortho - 1.5-2yr
Post-surgical ortho - 6m-1y
May require 3 years for combined orthodontic-orthognathic treatment
What is difficult about the pre-surgery ortho
- teeth compensate for skeletal discrepancies to function so pt will have malocclusion
- orthognathic surgery requires ortho to prepare teeth for surgical block movement into place, therefore during pre-surgery ortho → patient looks worse and exaggerates their malocclusion
(patient commitment of around 3 years + big surgical insult)
What is done during Le Fort 1 Osteotomy
- mx osteotomy sectioning lateral walls of mx sinus and lateral walls of nose
- sited ABOVE apices of maxillary teeth
- anteriorly: nasal septum divided from maxillary crest, posteriorly: mx seperated from pterygoid plates
- down-fracture & mobilisation
- maxilla repositioning - A/P, sup/inf, R/L (sometimes all) or
- maxilla segmentalisation - correction of width, occlusal plane, dento-alveolar relations
- titanium mini-plates used to hold in place, IMF to ensure mx will heal in the best plate
Why is it important to be careful with blood vessels during Le Fort 1 osteotomy
greater palatine vessels keep the palate alive
What can a bilateral sagittal split osteotomy do? How is it done?
- advance/set back md
- correct rotations/adjust assymmetry
- close small open-bite discrepancies
- There is a natural cleavage plane between B and L cortical plates
- sagittal split into: proximal (condylar) fragment, distal (dento-alveolar) fragment - reposition this fragment (not condylar as you will dislocate jaw)
What is a genioplasty
- can be solitary procedure or adjunct
- advance or set back chin
- augmented/reduced vertical dimension
- rotated R or L - centre-line discrepancy
Implication of orthognathic surgery in cleft lip & palate
- cleft lip repair affects growth of maxilla and can have scarring
- cleft lip at birth/ in childhood leads to restriction of mx growth
- cleft palate may have lack of alveolar bone and delayed eruption and crowding
→ may have bone grafts etc in childhood, in young adulthood there may be need for complex orthognathic surgery to correct growth deformity primary in maxilla
Implication of orthognathic surgery in cleft lip & palate
- cleft lip repair affects growth of maxilla and can have scarring
- cleft lip at birth/ in childhood leads to restriction of mx growth
- cleft palate may have lack of alveolar bone and delayed eruption and crowding
→ may have bone grafts etc in childhood, in young adulthood there may be need for complex orthognathic surgery to correct growth deformity primary in maxilla
Other craniofacial syndromes
What is distraction osteogenesis
- based on principle of encouraging new biological bone formation
- corticotomy/osteotomy done and bony surfaces seperated by incremental traction when appliance is turned periodically in hopes of increasing new bone to fill the space
- there is a simulataneous soft tissue lengthening
- distraction can be I/O or E/O (for young children)
- latent period/early callus forms
- distraction phase started
- consolidation phase/ossification of callus
