Morphologic adaptation of temporomandibular joint after chincup therapy.

The purpose of this study was to clarify the morphologic changes of the temporomandibular joint (TMJ) after chincup application, with longitudinal TMJ cephalometric laminagraphs. The subjects were 19 prepubertal patients with true, mild skeletal Class III malocclusions with anterior crossbite. All underwent chincup therapy from the beginning of treatment. The control subjects were 16 patients with functional anterior crossbite, with normal jaw relationships. Cephalometric laminagraphs and lateral cephalograms were obtained before and after treatment. Statistical analysis of the data revealed the results as follows: (1) The chincup therapy changed the direction of growth of the mandible, especially, the ramus swing-back. (2) The chincup group showed a relatively more slender mandibular neck compared with the control group. (3) The condylar heads were bent forward after the chincup application, and the glenoid fossa was deepened and widened. The clearance between condyles and fossae was decreased by the orthopedic force of the chincup appliance.