両側下顎臼歯部欠損による顎関節への影響に関する実験的研究

Abstract

Temporomandibular disorder has been showing an increasing tendency yearly and been attracting attention not only from the field of oral surgery but also from other fields in dentistry. The relations between temporomandibular disorder and occlusal disharmony, in particular, have been under discussion, but many matters still remain unclear. A study, therefore, was made to determine the effects of teeth loss, an occlusal disharmony, on the temporomandibular joint. Nineteen rhesus monkeys, whose temporomandibular joints most resemble human's, were used. The teeth in the bilateral mandibular molar region were extracted and the temporomandibular joint were investigated histopathologically. The results wereas follows : 1. In the condylar cartilagenous zone, thinning began on the 15th day from the anterior condylar region to the region opposite the narrowest part of the articular disc and progressed daily thereafter. In the posterior condylar region, thickening began on the 15th day and thinning was seen on the 60th day and thereafter. 2. In the internal anterior surface of condyle, bone resorption began early, became significant on the 60th day, became inactive thereafter, and ceased on the 180th day. 3. In the anterior region of the articular fossa, thickening of fibrous covering, proliferation of fibrous connective tissue, and thinning of the cartilagenous zone were observed on the 10th day and progressed daily thereafter. 4. In the anterior wall of the postglenoid process, bone resorption began on the 15th day and became significant on the 60th day. On the 90th day, bone resorption and bone apposition were seen concurrently. Thereafter, bone apposition was active but ceased on the 180th day. 5. Histological changes in the articular disc occurred late as compared with the condyle and articular fossa. However, in a longer period, the clone-forming of cartilage-like cells and the lip of connective tissue appeared in the post band. In the inferior region of the post band, fibrous bundles were arranged sparsely and ruptures were seen in part. 6. In the posterior region of the upper articular cavity, proliferation of villies and fat cells was observed. 7. No significant differences in these findings were observed between the left and right temporomandibular joints. As described above, teeth loss in the bilateral mandibular molar region caused instability of the condyle in the articular fossa and the condyle was postulated to exert pressure towards the postglenoid process.