The stability of bimaxillary osteotomy after correction of skeletal Class II malocclusion.

This study investigates changes following bimaxillary osteotomy for correction of Class II malocclusion. The records of 15 patients who had simultaneous maxillary impaction and sagittal split ramus osteotomy with rigid fixation are evaluated. Traditional cephalometric analysis as well as finite element and Euclidean distance matrix analyses are used to assess the changes. The maxilla was relatively more stable than the mandible; the maxilla stayed within 1 mm of its immediate postoperative position, whereas the mandible was 2 mm from the achieved surgical changes. The mandible rotated in a clockwise direction during the first 6 months after surgery. The mandibular plane angle increased by 2.9 degrees. This is, in part, believed to be due to posterior condylar displacement during surgery. Theories of mandibular relapse following sagittal split advancement osteotomy are discussed. The new methods of morphometric analysis do not require the superimposition of cephalograms and are able to separate maxillary from mandibular changes.