Transcript Principles of Orthognathic Surgery

Principles of Orthognathic Surgery
Prof Jayantha Weerasinghe
Orthognathic Surgery
• Jaw corrective surgery
• Correction of facial, skeletal and dental abnormalities
• Normally performed after cessation of facial growth
(>17 yrs of age)
• Planning period: Orthodontist, OMF Surgeon
• Pre- Surgical Orthodontic treatment
• Operative procedure – skeletal/ soft tissue
– Osteotomy
– Ostectomy
– Osteodistraction
• Post Surgical Orthodontics treatment
• Review
Facial, skeletal and dental abnormalities
• Facial
– Upper face- normal,
– mid face- Lip seal, short upper lip, competency of oral seal
– lower face- chin appearance
small or large size
- Unilateral or Bilateral
skeletal
abnormalities
dental
• Class I
normal maxillo-mandibular
relation
• Angle’s Classification:
first molar relationship
• Class I - normal
• Class II
Horizontally excessive maxilla
• Class II – excessive maxillary
• Class III
Horizontally excessive
mandible
• Pseudo relationships
• Shifting of midline
• Class III- excessive mandibular
• Other malocclusal features
cross bite, rotation, tilt
• Shifting of midline
Causes of facial, skeletal, dental abnormalities
Congenital- present at birth
• micrognathia – small chin/mandible
• Cleft Lip and Palate – retruded maxilla
• Syndromes- Pierre- Robin Sequence
Developmental- appear with facial development
• Horizontal/vertical excess of mandible/maxilla
• Midline shift due to lack/abnormal growth in
one side
– Condylar hypoplasia (Uni or bilateral)
– Hemi-facial microsomia
Habits/trauma/disease conditions
• Abnormal position, arrangement of teeth
Planning period: Orthodontist, OMF Surgeon
joint discussions
• Full face
photographs
• Cephalometric
analysis
• Study models
• Model surgery
• Virtual
assessment
(Computer based)
Pre- Surgical Orthodontic treatment
• Usually takes 1 year
• Correcting the occlusion to
match the post operative
skeletal situation
• Creates spaces for bone
cuts
• Occludes unnecessary
spaces
Operative procedure – skeletal/ soft tissue
• Osteotomy
– Make bone cutes to move segments
• Ostectomy
– Make bone cuts to remove a piece of bone
• Osteodistraction
– Make bone cuts and insert osteo-distractor device to move
bone segments
Maxillary - Procedures
Anterior segmental ostectomy
Le-Fort I/II osteotomy and downfracture to mobilize
• Access – U shape incision along
buccal sulcus
• Bone cuts- made above roots of
teeth
• Splitting of pterygoid plates from
maxilla
• Down fracture and bone plate
fixation
• Complications- blood supply is
compromised
Mandibular procedures
Bilateral Saggittal Split Osteotomy (BSSO)
Vertical Sub Sigmoid Osteotomy (VSSO)
Genioplasty
Mandibular procedures
Bilateral Saggittal Split Osteotomy (BSSO)
• Incision- bilateral extended third
molar incisions
• Buccal and lingual aspect of ramus
exposed
• Bone cuts made using saw
• Osteotomes to mobilize bone
segments
• ID nerve bundle to retain in the distal
segment
• Bone plate fixation buccally
• Complications
Injury to ID nerve bundle
Mandibular procedures
Vertical Sub Sigmoid Osteotomy
(VSSO)
• Extra-oral incision- submandibular
approach
• Vertical bone cuts – from lower
border to sigmoid notch behind
the ID foramen
• Bone plate fixation
• Complicationsexternal scar
Injury to marginal mandibular nerve
Mandibular procedures
Genioplasty
• Reduction of excessive
chin
• Augmentation of short
chin
• Intra-oral approachlabial sulcus deglove
approach
• Bone cut below roots of
anterior teeth
• Reposition and bone
plate fixation with or
without autogenous
bone graft
Combined ProceduresBi-maxillary Surgery
• Simultaneous two
jaw procedures
• Maxillary
advancement and
mandibular setback
• http://www.youtub
e.com/watch?v=4j8
zvEGkN2M&feature
=player_detailpage
Osteo-distraction short mandible
• Distraction osteogenesis is a surgical
process which can used to
reconstruct skeletal deformities
– Fracture the bone segments
– distraction phase
– consolidation phase
• Device – intra or extra oral
• Patient/parents trained to activate
daily
Adult Cleft Lip and Palate cases
Orthognathic Surgery or Oseo-distraction ?
• Scarring of maxilla make
movement of bone segements
difficult- surgery may not
achieve required bone
movement
• Blood supply to hard palate is
already compromised – making
risk of healing
• Osteodistraction if being
considered in many centres