[Changes of the temporomandibular joint following orthognathic surgery on radiography].

OBJECTIVE: To investigate the effect of different operative techniques and fixed methods on the TMJ condylar position and remolding process. METHODS: The standard Schuller's position radiographs were used to examine the postoperative temporomandibular joint form and condylar position changes of 57 cases within one week and one year after orthognathic surgery. The form changes were divided into three types. Type I was that the joint form was normal or abnormal before the operation and no significant change was found after the operation. Type II was that the joint form was abnormal before but after the operation it was improved. Type III was that the joint form was normal before but after the operation it changed into abnormal or it was abnormal before but after the operation it worsened. RESULTS: 1. Changes of the condylar position had happened after the operations, but within one year the condyles had resumed the same position as the preoperative. The condylar displacements were not beyond the TMJ adaptabilities. Different operative techniques had different effects on the condylar positions. 2. In 86.4% of cases, TMJs had undergone adaptable remolding (Type II) or no significant changes (Type I). Only 13.6% of cases, degenerative changes were found (Type III). CONCLUSIONS: The effect of orthognathic surgery on the condylar position and TMJ form is significant, but most of the changes are within the normal adaptability of TMJ.