| [Objective] To build an animal model to investigate the effect of Muscles’ Imbalance on the bilateral condylar subchondral bone, and assess the role of stress in the mechanism of condylar subchondral bone reconstruction.[Methods] Forty-eight 9-week-old male rats were randomly divided in to 4 groups: excise the coracoid group; botulinum neurotoxin A masseter injection group (masseter blocking group); excise the coracoid and botulinum neurotoxin A masseter injection group (combined surgery group) and control group, each group of 12 SD rats and were performed the corresponding operation on the right side, the rats were killed at the end of 2th,4th,8th and 12th weeks, three rats in each group during each period, acquire TMJ condylar and observe its Histological changes.1.observed the changes in the condylar cartilage surface; 2. The condylar were used for HE staining and observed the structual changes of condylar subchondral bones; 3. The expression of OPG and RANKL in condylar subchondral bones was observed by immunohistochemical staining and observed the changes of time and space of OPG/RANKL expression.[Results] 1.There were no significant differences in bilateral condylar surface between coracoid resection group and masseter blocking group with blank control group by observation visually. Combined surgery group, the surgerical side of articular cartilage surface lost luster, rough owe flat, and could be observed erosion lesions.2. HE staining showed that in there experimental group, TMJ condylar subchondral bone trabeculaes had disorder arrangement, and in combined surgery group surgerical side at 4 weeks after surgery,have observed the appearance of angiogenesis on the osteochondral junction and even extended to the cartilage layer. The analysis of bone morphometry showed that there were no significant statistical difference between three experimental groups sides of surgical and non-surgical side (p> 0.05); In the experimental groups, the number and density of bone trabecular were lower than the blank control group at 2,4 weeks after surgery (p< 0.05), and had no statistical difference with blank control group after 8,12weeks (p> 0.05); the number of trabecular bone clearance at 2,4 weeks after surgery was higher than the blank control group (p< 0.05), and had no statistical difference with blank control group after 8,12weeks (p> 0.05); the thickness bone trabecular at 2 weeks after surgery was lower than the blank control group (p< 0.05), and 12 weeks after surgery was higher than the blank control group (p< 0.05), and had no statistical difference with blank control group after 4,8 weeks (p> 0.05).3. Immunohistochemical showed:at the same time the expression of OPG and RANKL and ratio of OPG/RANKL had no statistical difference in each group side of surgical and non-surgical side (p> 0.05). After 2 weeks, the expression of OPG in the experimental groups were higher than blank control group (p< 0.05), and had no statistical difference with blank control group after 4,8,12weeks (p> 0.05). The expression of RANKL were higher than blank control group after 2,4weeks(p< 0.05), and had no statistical difference with blank control group after 8,12 weeks (p> 0.05);The ratio of OPG/RANKL in experimental groups were lower than the blank control group after 2,4 weeks(p< 0.05), and had no statistical difference with the blank control group after 8,12 weeks(p> 0.05).[Conclusions] 1. By coracoid removed and (or) masseter blocked establishes animal model of SD rats Muscles’ Imbalance successfully.2. Muscles’ Imbalance can induce disordered arrangement of bilateral TMJ condylar subchondral bone.and the most obvious after 2,4 weeks surgery.3. By OPG/RANKL signaling pathways, Muscles’ Imbalance involved in pathologic reconstruction of the bilateral TMJ condylar subchondral bone.4. Muscles’ Imbalance might be one of the reasons of inducing the temporomandibular joint osteoarthrosis. |
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