[An experimental study on change on the contralateral temporomandibular joint after unilateral condylectomy on one of the bilateral joints].

In this study I examined the macroscopic, radiological and histopathological changes on the contralateral temporomandibular joint following condylectomy on one of the bilateral temporomandibular joints on adult female Macaca fuscatas. I made a standardized radiographic apparatus for the temporomandibular joint and head for the Macaca fuscata on an experimental basis for radiological observation through the whole passage of time before making the experiment. The results were as follows: 1) In macroscopic observation, I noticed the entire mandible directed toward the operated side at opening the mandible and the anterior and molar (unoperated side) open bite after the operation. Besides the masticatory side altered and the degree of tooth attrition made progress with the passage of time. 2) According to radiographic investigation with an anteroposterior radiograph, complicated shift and rotation of the mandible were observed since the operation. According to the radiograph of condyle, distal displacement of the temporomandibular joint, widening of joint space and clockwise rotation of the mandible were confirmed. A shadow of bone was found in the articular surface of the mandibular head on the 123rd day. 3) The following findings were obtained in histopathology. (1) Heterotopic calcification appeared in an articular disk of one Macaca fuscata in control group and two in the 83rd-day-passaged Macaca fuscatas. (2) In the articular disk and the tissue around them, a tiny projection of connective tissue appeared in the posterior synovial portion of the superior articular cavity on the 10th day. And the intermediate zone of the articular disk showed itself to be fibrous small bundle daily as days passed on and cartilaginoid cells were found. (3) In the front edge of mandibular corpus and attachment region of the lateral pterygoid muscle, absorption of bone was observed by the 40th day from the operation, and additions of bone were observed during the period between the 40th and 83rd days from the operation. (4) The thickness of the cartilaginous lamina of mandibular head and fibrous velum varied much in different periods and areas. In the 83rd-day-passaged sample, osteosclerotic change and the irregularity on the articular surface were remarkably noticed. On the 123rd day the back of the mandibular head and the contralateral front wall of the back of the articular process showed absorption of the bone on a large part. (5) A large part of the articular surface in articular tubercle was irregular and some osteosclerotic change was observed. And on the 83rd day a good number of clones of cartilage cells were found.