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

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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.