Johji Kawakami

Histologic study of synovitis induced by trauma to the rat temporomandibular joint

OBJECTIVE The purpose of this study was to establish and histologically examine the time course of synovitis induced by trauma to the rat temporomandibular joint. STUDY DESIGN Synovitis of the temporomandibular 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 and 5 days and 2, 4, 6, 8, 10, and 20 weeks after treatment. RESULTS Histologic findings from the 5th day to the 6th week after treatment were characterized by multiple layers of synovial cells, an increase of dilated vasculature, fibrin deposits, and synovial adhesion. These findings were in good agreement with those reported for the human temporomandibular joint. The pathologic changes decreased with advancing time, and synovitis was not observed at 20 weeks after treatment. CONCLUSION The present procedure for inducing synovitis of the temporomandibular joint in rats will be useful in understanding the pathogenesis of synovitis in human temporomandibular joints.

The position of the mandibular condyle at maximal mouth opening in normal subjects

PURPOSE To investigate the position of the mandibular condyle at maximal mouth opening in individuals 19 to 30 years of age with no functional disorders of the masticatory system. PATIENTS AND METHODS Measurements were made in 153 subjects (99 men, 54 women), and 41 men and 44 women had transcranial radiographs taken of their right and left temporomandibular joints in the closed and maximal opening positions. RESULTS In all subjects the condyle moved forward beyond the summit of the articular eminence, and in more than half the subjects the condyle was located inferior to the eminence at maximal opening. CONCLUSION The correlation between maximal opening and anterior shift of the condyle from the summit of the eminence was significant, but the correlation with vertical shift of the condyle was not significant. The correlation between the form of the glenoid fossa (length and depth) and anterior or vertical shift of the condyle from the summit of the eminence also was not significant.

Development and histologic characteristics of synovitis induced by trauma in the rat temporomandibular joint

Histopathological changes caused by trauma to the rat temporomandibular joint synovium were examined by light microscopy. The trauma was induced by forced hypermobility of the condyle. Pathological changes of the synovium were found primarily in the anterior pouch of the upper joint compartment. The main findings included surface cell proliferation, increased capillary hyperemia, fibrin deposits on the surfaces of inflamed synovial membranes, and fibrinous adhesion between closely opposed synovial membranes. A gradual change from fibrinous adhesion to fibrous adhesion was also seen.