Skeletal relapse and dental change during intermaxillary fixation after mandibular setback

Chang, Chong On

Abstract

It has been reported that skeletal relapse and dental change after mandibular setback do occur not only after intermaxillary fixation(IMF) removal but also during IMF. The side effects of skeletal relapse during IMF have clinical importance because they can cause many postoperative orthodontic problems. Generally, the prevention of solid union between segments, compensatory tooth movement, anterior openbite, etc. have been cited as the side effects fo jaw displacement. The purpose of this study was to evaluate the skeletal relapse and dental change during IMF. material consisted of 28 patients who were treated by BSSRO(bilateral sagittal split ramus osteotomy), wire osteosynthesis, IMF for correction of mandibular prognathism. Through cephalometric analysis, the amount and direction of surgical movement, skeletal relapse and dental change during IMF were measured. The correlation between surgical movement and skeletal relapse, between skeletal relapse and dental changes were evaluated. 1. Distal segment was repositioned backward and upward, proximal segment showed clockwise rotation during surgery. 2. During IMF, anterior portion of distal segment was displaced backward and posterior portion was displaced up ward. Proximal segment was displaced upward with forward movement of Go(gonion of proximal segment). Backward surgical movement of p-Go was significantly correlated with forward displacement of p-Go. 3. Overjet and overbite were not changed during IMF. The compensatory tooth movements during IMF were characterized by retroclination of upper incisors and retroclination, extrusion of lower incisors. These compensatory tooth movements had statistically significant correlation with upward displacement of d-Go(gonion of distal segment).