HISTOLOGIC-STUDY OF SYNOVITIS INDUCED BY TRAUMA TO THE RAT TEMPOROMANDIBULAR-JOINT

Objective. The purpose of this study was to establish and histological ly examine the time course of synovitis induced by trauma to the rat t emporomandibular joint Study design. Synovitis of the temporomandibula r joints of 8-week-old male Wister rats was induced by forced condylar hypermobility which was administered 10 times successively once a day for 10 days. Pathologic changes were observed microscopically at 2 an d 5 days and 2, 4, 6, 8, 10, and 20 weeks after treatment. Results. Hi stologic findings from the 5th day to the 6th week after treatment wer e characterized by multiple layers of synovial cells, an increase of d ilated vasculature, fibrin deposits, and synovial adhesion. These find ings were in good agreement with those reported for the human temporom andibular joint. The pathologic changes decreased with advancing time, and synovitis was not observed at 20 weeks after treatment. Conclusio n. The present procedure for inducing synovitis of the temporomandibul ar joint in rats will be useful in understanding the pathogenesis of s ynovitis in human temporomandibular joints.