Study on the Effect of Edentulousness Induced Degenerative Changes in SD Rats' Mandible Condyle

Objective: To investigate whether the edentulousness can induce degenerative changes in rats'TMJ. Methods: 54 female SD rats, aged 70 days, were divided equally and randomly into three groups. Group A: all molars were extracted and all incisors were sheared. Group B: only upper jaw molars were extracted and upper jaw incisors were sheared. Group C:no tooth was extracted or sheared as control. All animals were raised in the same way. At the time of 4, 12 and 24 weeks after operation, six rats of each group were killed by deeply anaesthetizing. One side condyles of TMJs were sectioned and stained with HE, the other side condyles of TMJs were observed by scanning electron microscope. Results: The cartilage of TMJs in group A and B were found with significant degenerative changes and these changes increased with time prolonged after operation,which included the cartilage thickness of anterior and intermediate part of condyle decreased, the disturbance of continuation of intermediate hypertrophic layer appeared and part of them locally replaced by fibrous tissue. The micrographs of the condylar surface was inordinate,the gelation material of condylar surface in group A and B was lost,and the collagen tissue of deep layer exposed. Conclusion: The edentulousness may lead to degenerative changes in rats'TMJ.