Abstract
The purpose of this study was to investigate the long-term dentofacial changes following sagittal splitting ramus osteotomy in mandibular prognathism patients and to clarify morphologic factors relevant to the stability of occlusion during the retention period.Lateral cephalograms of 19 patients (5 males and 14 females), observed for more than three years after the end of active treatment, were analyzed for evaluation of dentofacial changes. The materials were obtained at five stages: before treatment, immediately before surgery, at removal of intermaxillary fixation, at the end of active treatment and at the last. Dentofacial changes were analyzed and compared between the stages.The results were as follows:1. During the preoperative orthodontic treatment, the mandibular incisors were inclined labially and menton was displaced downward.Menton was moved backward 11.1mm on average by surgery. The maxillary and mandibular incisors moved lingually and elongated during intermaxillary fixation.During the postoperative orthodontic period, menton was displaced forward and upward (average; anteriorly 2.6mm, superiorly 0.6mm). A correlation was found between the amounts of mandibular setback and forward displacement of menton. The maxillary incisors were inclined labially.During retention, the menton was displaced downward and mandibular incisors were slightly inclined labially.2. Overjet and overbite tended to decrease slightly during the retention period. At the end of treatment, an acceptable occlusal relationship in the anterior region was maintained in most cases. Two patients showed edge-to-edge occlusion and one of them showed open bite.No correlation was found between the dentofacial morphology before treatment and changes in overjet or overbite. A significant correlation was found between the amount of mandibular setback and the decrease in overbite. Vertical changes in menton and labial inclination of mandibular incisors during the retention period play a significant role in the occlusal stability after orthognathic surgery.
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