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ABSTRACT
Although excessive mechanical stress is assumed to be one of the factors contributing to pathogenesis of temporomandibular joint (TMJ) osteoarthritis (OA), no pure mechanical-stress-induced OA model has been developed without surgical manipulation or puncture of the joint cavity. The purpose of this study was to establish a genuine mechanical-stress-induced OA model of the rabbit TMJ. In the experimental rabbits, repetitive, forced jaw-opening, 3 hrs/day for 5 days, was applied with the use of a general anesthesia protocol. By histological assessment of the TMJ articular tissues, partial eburnation of the articular cartilage, reactive marginal proliferation of the articular cartilage chondrocytes, and nested proliferation of chondrocytes in the subchondral bone area were observed at 7 days after the repetitive, forced-jaw-opening period. These results suggest that the repetitive, forced-jaw-opening protocol without surgical intervention can induce evident OA-like lesions in the rabbit TMJ, and this OA model may greatly contribute to the elucidation of the cartilage degradation mechanism in TMJ OA.
KEY WORDS: articular cartilage, temporo-mandibular joint, mechanical stress, osteoarthritis.
Received May 24, 2002; Last revision May 14, 2003; Accepted May 27, 2003
INTRODUCTION
Osteoarthritis (OA) is a degenerative joint disease that is characterized by articular cartilage degradation and concomitant reparative/adaptive osteogenesis. Excessive mechanical stress has been recognized as one of the major implicating factors in OA. However, the exact role of the excessive joint loading on the degradation process is still unclear.
Several experimental temporomandibular joint (TMJ) OA models have been developed by some researchers to elucidate the relationship between adverse mechanical stress and OA pathology. In some of those OA models, surgical manipulation of the joint structures was performed to alter intracapsular mechanical circumstances, e.g., discectomy (Takatsuka et al., 1996; Bjornland and Haanaes, 1999), surgical induction of disk displacement (Silbermann, 1976; Ali and Sharawy, 1994), and disk perforation (Axelsson et al., 1992; Sato et al., 1998). However, these kinds of surgical procedures induced not only mechanical alteration, but also artificial surgical damage to the joint structures. Therefore, these OA models cannot be regarded as a real mechanical-stress-induced OA model that is comparable with a clinical disorder of spontaneous TMJ OA.
Recently, a forced-jaw-opening protocol has been shown to be effective in inducing articular synovitis in the TMJ (Chiang and Kakudo, 1990; Muto et al.,...