[An experimental study on change in temporomandibular joint following occlusal changes]

In order to clarify the cause of temporomandibular arthrosis, an experimental study on change in temporomandibular joint resulting from faulty occlusion which is thought to be one of the causes was performed. In this study, macroscopic, radiologic and histopathologic effects of a forced distal positioning of the mandible by occlusal metal splints and loss of posterior teeth in adult Macaca fuscatas were observed. Cephalometric radiograph including posteroanterior and axial projection were taken to determine the individual projection angle for standardized TMJ radiography including lateral oblique transcranial and transpharyngeal projection prior to the experimental procedures. The upper and lower molars of the monkey were extracted and the remaining teeth were prepared and the cast metal splints were adhered in place. They were maintained on their regular diet. Radiographic observation of the joints and macroscopic clinical observation of the occlusion were made individually, immediately after operation, at the 10th, 20th, 40th and 83rd day postoperatively. The monkeys were killed individually at the 10th, 20th, 40th and 83rd day postoperatively, each temporomandibular joints were removed and prepared for contact microradiographic, fluorescent micrographic and histopathologic observations. The results obtained were as follows: 1) Macroscopically, the opening between the upper and lower lateral teeth in full closure was about 2mm, overbite about 2mm in anterior teeth immediately after the splints were adhered in place and molar extraction. The opening between the lateral teeth decreased slowly after the 10th day postoperatively and they were approximating occlusal contact from the distal area of the splints. The whole area of the occlusal surface of the splints came into contact and the mandible positioned posteriorly by the 40th day. 2) Though the cephalometric radiographs in posteroanterior and axial projection did not show the changes of mandible through the whole experimental period, lateral head plates and standardized TMJ radiographs showed posterosuperior positioning of the mandible after 20th day postoperatively, and osseous absorption in the posterior aspect of the condyle at the 83rd day. 3) Contact microradiographic and fluorescent micrographic observations showed osseous remodeling in the neck of condyle at the site of the insertion of the lateral pterygoid muscle, anterior aspect of the retroarticular process and posterior aspect of the condyle.(ABSTRACT TRUNCATED AT 400 WORDS)