Bone Abstracts

Introduction: Low level of estrogen has regarded as a main contributing factor of temporomandibular joint (TMJ) arthritis in young women patients. However, there is lack of evidence about the occurrence of arthritis in knee joint (KJ) related with estrogen deficiency. This study aimed to investigate the effect of estrogen deficiency on the loaded and non-loaded bone area of TMJ or KJ.

Method and materials: Total of 28 SD rats were allocated into two groups, the sham surgery group and the ovariectomy (OVX) group. TMJ was subjected to mechanical loading with elastic power chain between mandibular angle and zygoma in half of animals. At 12 weeks after OVX, all groups were scarified. Changes in the bone area of KJ and TMJ were analyzed using micro-computertomography (micro-CT).

Results: We analyzed the bone area of joint region in TMJ and KJ each which was compartmentalized into three areas on loaded, middle and non-loaded area. Bone mineral density (BMD) and three-dimensional micro-CT parameters were compared between TMJ and KJ. Non-loaded area of TMJ showed a significant decrease in bone volume/tissue volume (BV/TV) and BMD at ovariectomized rats, which was independent of mechanical loading. However, there was no difference in BV and BMD either in loaded area of TMJ or in all areas of KJ in both loaded and non-loaded OVX rats. Middle area of TMJ in OVX rats with or without loading showed a significant decrease in BV/TV, but no difference in BMD.

Conclusion: These results revealed that OVX-mediated estrogen deficiency led to a significant decrease of bone formation and quality in non-loaded bone area of TMJ and no influence on bone area of KJ, suggesting that TMJ is more sensitive to estrogen deficiency.