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[Bone mineral density (BMD) distribution in edentulous mandible--a measuring system for bone mineral content with computed radiography (CR)].

The purpose of this study was to develop a measuring system for bone mineral density(BMD) using computed radiography and to measure BMD distribution in the edentulous mandible. Nine 2-3 mm thick sequential cross-sectional bone slices were obtained from five cadaveric mandibles. Each slice in cross-sectional view on X-ray image was divided into 64 elements and BMD distribution was investigated. The results were as followed: 1. BMD measuring system: The accuracy was 1.4%(relative error) and the reproducibility was 1.1%(CV). 2. BMD distribution in edentulous mandible: 1) BMD varied from slice to slice, decreasing from anterior to posterior in both cortical and cancellous bone on the inferior and lingual side. The BMD of buccal cancellous bone was relatively higher than that of the lingual side and remained fairly constant throughout. The BMD of buccal cortical bone showed a slight posterior increase. 2) Greater individual variation of BMD was observed near mental foramen and in incisor lingual and inferior cancellous bone. Our system demonstrated excellent precision and reproducibility BMD distribution varied near regions of muscle attachment and the mandibular canal. Further, it was suggested that strong implant stability in the molar region may be obtained by installation of the fixtures in the buccal cancellous area.