Effect of aging and a tooth defect on the shape of mandible

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Bone mass is a key factor for success of various dental and oral treatment, and we consider about bone loss when applying dentures and dental implants to alveolar ridge. Despite the high risk for osteoporotic bone loss among the post menopausal elderly, effect of estrogen depletion on oral bones has been ambiguous. To determine if estrogen depletion and tooth extraction affects mandibular bone volume, we conducted the following experiments, using ovariectomized (OVX) rats. The first right molars of OVX and sham operated rats were extracted. 109 days postovariectomy, the rats were sacrificed and measured the bone mineral density of right mandibles with dual energy X-ray absorptiometry (DEXA) and peripheral Quantitative Computed Tomography (pQCT). Significant difference between OVX rats and sham rats was not detected when whole mandible bodies were scanned by DEXA.However, there was significant difference when the condyle was scanned. Further, trabecular bone mineral density and cortical bone mineral density around molars in the mandibles were separately measured with pQCT.In a limited area around the molars, trabecular bone mineral density was significantly decreased in the OVX group although cortical bone mineral density was not significantly different. By contrast, the maxillary molar extraction led to decrease in BMD though dit was not significant. In this study, the BMD of he condyle which is abound with trabecular bone and trabecular bone mineral density around molars were decreased in OVX rats. These results suggest that estrogen depletion mainly affects the trabecular bone in mandible. It will be necessary to conduct further experiments to clarify the effect of tooth extraction. Furthermore, we established a primary culture system dirived from rat bone marrow cells and have investigated anabolic or catabolic factor for bone.