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To investigate the histopathologic changes of the rabbit craniomandibular joint (CMJ), anterior disc displacement (ADD) was surgically induced. Of 15 rabbits, 9 were classified as experimental group, 3 as control group, and 3 as sham-operation group, respectively. The experimental group (9 rabbit) was subdivided into 6 weeks, 12 weeks, and 20 weeks group, respectively 3 rabbits. In experimental group, the disc was displaced anteriorly at the right side(operation side) and left CMJ was not operated(non-operation side). Both CMJs were harvested at 6, 12, and 20 weeks following surgery in experimental group. The CMJ was harvested at 6 weeks following surgery in sham-operation group. The specimens were examined under light microscope after hematoxylin-eosin and verhoeff staining. The obtained results were as follows: 1. In midsagittal view of control and sham-operation group, there were no degenerative and hyperplastic changes in the CMJ including articular disc, mandibular condyle, and temporal fossa. 2. Disc was shortened anterior-posteriorly and deformed of biconcave shape in all experimental group. In 20 week experimental group, intermediate zone of disc width was almost same as the width of posterior band of disc. 3. Soft tissue hyperplasia at the posterior attachment area of the disc and condylar hyperplasia were seen in the all experimental groups, but the degree of the hyperplasia was greater at 12, 20 weeks than at 6 weeks. 4. The number of elastic fiber in the disc proper was decreased and the direction and morphology was changed in all experimental groups compared with those of control groups. 5. Fatty degeneration was shown in non-operation side of 20 weeks experimental group. These results suggest that induced ADD in craniomandibular joint of rabbits could lead to a reparative and degenerative changes of the affected joint similar to those described for osteoarthrosis and osteoarthritis in human.
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