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

骨量是各种牙科和口腔治疗成功的关键因素，我们在牙槽嵴应用义齿和种植体时考虑到骨质流失。尽管绝经后老年人骨质疏松性骨质流失的风险很高，但雌激素消耗对口腔骨骼的影响一直不明确。为了确定雌激素消耗和拔牙是否会影响下颌骨体积，我们使用去卵巢（OVX）大鼠进行了以下实验。取出OVX大鼠和假手术大鼠的第一右磨牙。术后109 d处死大鼠，采用双能x线骨密度仪（DEXA）和外周定量计算机断层扫描（pQCT）测定右下颌骨骨密度。用DEXA对OVX大鼠和假手术大鼠进行全下颌骨扫描时，没有发现OVX大鼠与假手术大鼠的显著性差异。然而，当扫描髁时，有显著差异。应用pQCT分别测定下颌骨磨牙周围骨小梁骨密度和皮质骨密度。在磨牙周围有限区域，OVX组骨小梁骨密度显著降低，但皮质骨密度无显著差异。而拔除上颌磨牙对骨密度的影响不明显，但对骨密度的影响较小。在本研究中，OVX大鼠具有丰富骨小梁的髁骨骨密度和磨牙周围骨小梁骨密度降低。提示雌激素耗竭主要影响下颌骨的骨小梁。有必要进行进一步的实验来阐明拔牙的效果。此外，我们建立了大鼠骨髓细胞原代培养体系，并研究了骨的合成代谢因子和分解代谢因子。

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.