Facial frontal morphological changes related to mandibular setback osteotomy using cephalograms

Aim: The purpose of this study was to examine morphological changes of the mandibular region using frontal cephalograms following bilateral sagittal split osteotomy (BSSO) for mandibular setback. Furthermore, we compared the stability between screw and plate fixation. Methods: Pre and postoperative frontal cephalograms were taken of 26 patients. Parameters, Angle "A" which is formed by constructed lines along the mandibular ramus, and mandibular width at the angle were calculated. The subjects were analyzed according to the types of bony fixation, whether by screws or plates. Results: Angle "A" and mandibular angular width of total numbers did not widely change at early period following operation. Late postoperatively, mandibular width of total numbers decreased in conjunction with increasing Angle "A". When comparing the parameters between screw and plate groups, the plate group showed a decrease of Angle "A" as an early change. Late postoperatively, the plate group showed an increase of Angle "A" and a decrease of mandibular width, while the screw group had smaller changes. Conclusion: We demonstrate postoperative inclination of mandibular lower ramus towards the facial midline. We suggest that the types of rigid fixation have an influence on frontal skeletal morphology, namely that screw fixation has higher stability.