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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