Condylar displacement related to mandibular symphyseal distraction.

This study was undertaken to determine the true nature of condylar displacements associated with mandibular symphyseal distraction osteogenesis. Earlier investigators have assumed that each mandibular half rotated about a point near the center of each condyle as viewed on a submental radiograph. In a 12-patient sample, 10 with tooth-borne symphyseal distraction and 2 with bone-borne symphyseal distraction, it was found that each condyle was laterally displaced in direct relationship to the amount of symphyseal distraction. The rigidity of the distraction appliances and their attachments and the inability of the soft tissues and muscular attachments to cause the mandible to undergo compound bending require this to be the case. Temporomandibular joints appear to be able to accommodate the lateral displacements because symptoms were not introduced, or, if present before therapy, distraction did not exacerbate them.