Bone resorption effected by denture use and osteoporosis

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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.