Bone resorption effected by denture use and osteoporosis

骨矿含量(BMC)的研究有助于准确预测种植体治疗的预后和筛查骨质疏松。BMC可以用特殊的设备来测量，比如定量计算机断层扫描。本研究利用全景X线机对BMC测量系统进行了改进，一次可获得牙弓及相关结构的全程覆盖。在本研究中，我们将骨模用于参考和测试阶梯楔，X500CR(森田公司)用于全景X射线系统，Denoptix数字成像系统(Dentsply Co.Ltd.)用于图像输入设备。照射条件为60KV，10mAs。将参考阶梯固定在图像层左侧，改变测试阶梯的位置：1)层内或层外；2)前磨牙或磨牙区域。验证了该系统在各种条件下的测量精度和重复性，BMC测量分辨率为0.01~0.04 mg/cm2/像素，重复性为0.58~0.69%(CV)。蛋壳内外差异不显著(P&gt；0.05)。磨牙区的测量值高于前磨牙区(P&lt；0.05)。RMET值的变化是测量位置的函数(r=0.995~0.999)。RMET值的校正精度为1.25%(相对误差)。研究结果表明，RMET值到BMC值的转换减小了特定条件下测量位置变化对被测BMC的影响，测量系统能够提供稳定的数据。该系统对于种植体治疗的准确预测和骨质疏松的筛查是有用的。

The investigation of bone mineral content(BMC)is useful for an accurate prognosis for implant treatment and for osteoporosis screening. BMC can be measured by special devices, as quantitative computed tomography. In this study, BMC measuring system was improved by using panoramic X-ray system to obtain overall coverage of the dental arches and associated structures at a time. We surveyed the measuring performance of this system.We applied bone phantom to reference and test stepwedges, X500CR(Morita Co.Ltd.)to panoramic X-ray system and Denoptix digital imaging system(Dentsply Co.Ltd.)to image input device in this study. The exposure condition was 60kV, 10mAs. The reference stepwedge was fixed at left side on image layer, the position of test stepwedge was changed as followings 1)inside or outside of the layer, 2)premolar or molar region. We verified the measuring accuracy and reproducibility of this system at each condition.The resolution of BMC measuring was 0.01-0.04mg/cm^2 per pixel, the reproducibility was 0.58-0.69%(CV). The significant difference between inside and outside of the layer was not found(P>0.05). However, measured value in molar region was higher than that in premolar region(P<0.05). The change of RMET value was a function of the measurement position(r=0.995-0.999). The accuracy of adjusted RMET value was 1.25%(relative error).The results obtained in this study demonstrated that the conversion from RMET value to BMC value decreased the variation of measured BMC from change of setting position at a specific condition and that the measuring system was able to provide a stable data. This system may be useful for an accurate prognosis for implant treatment and for osteoporosis screening.