Quantitative Study in Absorption of Mandible Caused by Aging and Disease.

下颌骨吸收是由局部和全身疾病、年龄和修复因素共同作用的结果，即牙体修复对牙齿、下颌骨和剩余牙槽嵴的局部刺激。为了了解下颌骨的吸收情况，需要了解下颌骨的吸收与义齿局部刺激以及老年人易患的骨质疏松等骨病之间的关系。对骨质疏松症的筛查也是必要的，从生物化学、组织学、放射学等方面对骨吸收进行了大量的研究。近年来，骨小梁密度的变化已成为人们关注的焦点。但是，目前还没有定量的研究，吸收的madible。一些测量系统对设备要求较高，目前还没有一种简单的方法可以对骨矿含量进行高精度的测量，因此我们研制了一种基于计算机X线摄影系统的测量系统，并得到了广泛的应用。该系统包括Sn、Cds过滤和10 cm的空气间隙，Sn、Cds过滤产生非常小的管电位变化和光密度不均匀性的影响，空气间隙减少散射分数对对比度改善的影响。在0 ~ 800 mg/cm ~ 2范围内，测量误差小于10 mg/cm ~ 2，可用于检测骨小梁密度的变化。使用Kedge电位比Cd或Sn低的滤光片可以扩大测量范围。

Absorption of mandible is caused by both local and general disease as well as aging and prosthetic factors, that is local stimuli on teeth, mandibular bone and residual ridge caused by dental prostheses. It is useful information for prosthetic treatment, design and prognosis of prosthetics.To understand absorption of mandible, we need to know relations among absorption of mandible, local stimuli which denture makes and bone disease like osteoporosis which aged people is susceptible to. It is also be necessary to seek possibility of screening people suffering from osteoporosis.There are many studies in absorption of madible with biochemistry, histology and radiology. Recently changes of trabecular bone mineral density have become a center of attraction. However, there is no quantitative study in absorption of madible. Some measurement system requires particular facilities, and there is no simple method which can make high-accuracy measurements of bone mineral content.Thus, we developed a measurement sytem which is based on computed radiography system, coming into wide use. This system includes a Sn, Cds filtration which produces very rittle effect of tube potential change and unevenness of photo density and an air gap of 10 cm which reduce effect of scattered fraction for contrast improvement. Accordingly a measurement error was less than 10mg/cm^2 in range from 0 to 800mg/cm^2, and it was found that this system is useful for detecting changes of trabecular bone mineral density. Using filter which has lower Kedge potential than Cd or Sn may allow us to expand the range of measurement.