Objective This article was to study the effect of induced occlusal disorders and removed occlusal disorders on the expression of bone morphogenetic protein- 2（BMP- 2） of condylar cartilage. Methods Young and adult female Sprague- Dawley rats were divided respectively into induced occlusal disorders group, removed occlusal disorders group and control group, 3 rats every group. For induced occlusal disorders rats, the elastic rubbers were inserted between the first and second molar in the left upper side and right lower side to form the disordered occlusion. They were killed under anaesthesia 8 weeks after the treatment. For removed occlusal disorders rats, the first molars that caused disordered occlusion were extracted 6 weeks after forming disordered occlusion. 2 weeks later , they were killed under anaesthesia. For normal rats, they were killed at the same time with experimental rats. Hibateral temporomandibular joints of each rat were removed and stained with HE and monoclone antibody of BMP- 2. The thickness of condylar cartilage was measured. The expression of BMP- 2 in condylar cartilage was detected by half- quantity immunohistochemical analysis. Results For adult induced occlusal disorders group, the thickness of cartilage in intermediate part of condyle decreased. However, it increased in the posterior part. After removing occlusal disorders, the thickness of posterior condylar cartilage returned to normal level. But it was still thinner than control group in the intermediate part. The expression of BMP- 2 in anterior, intermediate, posterior part of condylar cartilage of young induced occlusal disorders group was higher than that of young removed occlusal disorders group and control group. No difference of the expression of BMP- 2 was found in young removed occlusal disorders group and control group. For the expression of BMP- 2 in intermediate part of condylar cartilage, both adult induced and removed occlusal disorders groups were higher than adult control group. For the posterior part of adult condyle cartilage, the expression of BMP - 2 showed induced occlusal disorders group was higher than removed occlusal disorders group, which was higher than control group. Conclusion Induced occlusal disorders can lead higher expression of BMP- 2 in condylar cartilage of young and adult rats. Adaptability of condylar cartilage of adult rats is weaker than young rats, especially the intermediate part.
