Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Oral and Maxillofacial Surgery

Aim: to assess the accuracy of condylar/ proximal segment position after BSSO using osteotomy / screw holes and plate locating surgical guides. Methodology: Ten patients were selected complaining of skeletal class II or class III malocclusion that required orthognathic surgery for correction of mandibular deformities. A preoperative assessment of all patients carried out including history taking, clinical, photographic, radiographic examination, three-dimensional analysis, and virtual planning. Work up and Plan Execution: A preoperative (CT) was acquired while the patient bites on his own registration wafer , the obtained CT Dicom files and scanned casts were imported into (mimics) software to form a 3D composite skull model , after virtual model surgery, the corrected 3D mandible model was printed and 0.2 mm thickness titanium mini plates bent and fixed over the mandibular model. Then the model with the fixed pre-bent plates were laser scanned to generate the osteotomy/screw holes locating and plate locating surgical guides Surgical Procedures: Owbgeser incision was performed to expose the buccal and lingual aspects of the ramus angle region, Osteotomy/screw holes locating guide was anatomically placed and fixed. The medial and vertical osteotomies together with the plates{u2019} screw holes were performed through the guide. The osteotomy/screw holes locating surgical guide remsegments at the level of the anterior boarder of the ramus and accommodated the plate inside .Plate fixation was performed using 2.0 screws. , A CT scan was performed 3-7 days postoperatively, a full assessment of the condylar deviation between preoperative and postoperative position was performed. Results: The twenty condyles showed accurate clinical position with (0.71±0.66{u00B0} - 1.27±0.71{u00B0}) angular deviation and (0.40±0.23 mm - 0.64±0.34 mm) linear deviation which is less than the clinically acceptable range reported in the literature (1mm/4{u00B0})

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