The purpose of this sutudy was twofold; the first purpose is to ascertain the direction of condyla displacement and changes of joint space in patient receiving mandibular ramus osteotomy for the inandiNll´ prognathism. the second purpose is to determine whether a significant relation exists between joint changes and postoperative skeletal changes. The material of this study was composed of 16 patients vno operated for mandibular prognathism by sagittal split osteotomy(n=fi) and vertical ramal osteotomy (n=8). Ead patient had a radiographic taken. Cephalometric radiographs were performed preoperatively, imniediatt postoperatively, andat least 6 months after surgery. TMJ tomograms were taken within 1 week preoperati and 6-24months later after the surgery.
The results were as follows
1. On lateral cephalogram, there were significant decreases in posterior facial height, SNB angle, SNPo angle and correction of anterior crossbite, as the mandible was surgically retruded.
2. The `mandibular condyles had tendencies for displacement to anterosuperior direction in SSRO group and t anteroinferior direction in VRO group.
3. On TMJ tomogam, although there were tendencies for decreases anterior, posterior joint space, and inch posterior joint space in SSRO group, there were noe statistically significant(p>0.05). In VRO group, alth uu; there were tendencies for increases anterior, superior, and posterior joint space, there also were nc
significant(p>0.05).
4. There were existed some correlation between joint space change due to condylar displacement and skelet relapse. It seemed that postoperative skeletal relapse was influenced by condylar displacement afte mandibular setback by ramal osteotomy.
5. The bony changes after mandibular ramus osteotomy for mandibular prognathism were noted as doi,hl contour on the posterior part of the condylar head, and flattening on the anterosuperior part of the cond; 1, head.
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