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The Chinese Journal of Dental Research

Year 2002
Volume 5 , Issue 3

Pages: 41 - 46

The Establishment of an Animal Model with TMJ Degenerative Changes Caused by Gradually Induced Occlusal Disorders

Jin Wu Chen, DDS/Mei Qing Wang, DDS/Yao Ping Wu, PhD

Objective: To establish an animal model of TMJ degenerative changes caused by gradually induced occlusal disorders (GIOD). Methods: Twenty-seven male New Zealand rabbits were divied equally and randomly into 3 groups: an experimental group, a blank control group, and a sham-operated control group. In the experimental group, the upper first premolar on one side and the lower premolar on the other side of 3 New Zealand rabbits were pulled with orthodontic strings, so as to make them incline medially to the anterior intrinsic space, thus inducing a convex-to-convex occlusal contact relationship. All the sham-operated controls were treated in the same way as those in the experimental group except for the pulling. At 1, 2, and 3 months after treatment, 3 rabbis from each group were sacrificed, respectively, and TMJ tissues were harvested. For each rabbit, the TMJ was bisected in a sagittal direction on one side and in a coronary direction on the other side. Serial stained sections that symbolized the anterior, intermediate and posterior, and the medial, center and lateral parts of condyles were then observed through a system consisting of lightscope, computer and relative graph measuring software. Each of 3 layers of the cartilage, and the cartilage as a whole, in all 3 of the separated portions described above were measured respectively for histometric analysis. Results: There was no significant histological difference in the condylar cartilage of the blank control group and the normal control group. Compared with the control groups, significant degenerative changes were found in the condyles of the experimental group. The main pathological characteristics were as follows. The thickness of cartilage in the anterior and intermediate parts of the condyles had decreased; the hypertrophic layer was disturbed and local hypertrophic layers were replaced by fibrous tissue that could even penetrate into the bone cavity. However, the thickness of cartilage in the posterior part of the condyle had increased; this increase was obviously associated with the increase of the proportion of immature chondrocytes. In the control groups, significant positive correlations were found between the thickness of the cartilage as a whole and the fibrous layer (r = 0.65), and proliferative layer (r = 0.64) and the hypertrophic layer (r = 0.75) respectively (P < 0.01). In the experimental group, a positive correlation was found only between the thicknesses of the whole cartilage and the hypertrophic layer (r = 0.68, P < 0.01). Conclusion: Occlusal disturbance resulting from gradually induced occlusal disorders in the premolars of rabbits may lead to degenerative changes in the condyle.



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