MEASUREMENT OF MANDIBULAR BONE-DENSITY EXVIVO AND INVIVO BY DUAL-ENERGY X-RAY ABSORPTIOMETRY

Severe bone resorption is a vexing clinical problem, especially in pat ients without teeth. To study resorption in vivo, measurements of bone mineral density (BMD) of the mandible of both patients with and witho ut teeth are needed. Using a Hologic QDR-1000 bone densitometer design ed to measure lumbar spine and hips, ex vivo and in vivo measurements were made in selected areas of the mandible. The mandible was position ed such that the X-ray beam was perpendicular to its sagittal plane. I n this way the beam hits first one half of the mandible and then the o ther. The reproducibility-expressed as coefficient of variation-of the ex vivo measurements was 0.5%. For in vivo measurements this coeffici ent was 3%. The method used for mandibular BMD would make it possible to define an average BMD in several categories of the normal populatio n and of patients, and to compare bone density in the mandible with th at in the axial and perpendicular skeleton. Improvement may be obtaine d by repeating the measurement. The entrance dose per scan is low, equ alling that of one bitewing/radiograph.