MANDIBULAR BONE-MINERAL DENSITY AS A PREDICTOR OF SKELETAL OSTEOPOROSIS

A considerable amount of work has been performed on methods of detecti ng individuals with low bone mass at an early stage. Some researchers have considered if dental radiographs could have a role in the detecti on of individuals with osteoporosis. A basic requirement for this woul d be that bone mass in the jaw relates significantly to that of other skeletal sites in which osteoporosis is a significant problem. The fir st aim of this study was to investigate the relationship between mandi bular bone mineral density (BMD) and that of other skeletal sites comm only used for bone densitometry in the detection of osteoporosis. The second aim was to assess the validity of mandibular BMD as a predictor of BMD in these other sites. 40 edentulous females underwent dual ene rgy X-ray absorptiometry (DXA) of the lumbar spine (L2-L4), DXA of the right femoral neck, single photon absorptiometry (SPA) of the proxima l and distal forearm and DXA of the mandible. Significant correlations were observed between BMD in the mandibular body, ramus and symphysis and all other skeletal sites (p<0.02). Five patients (12.5%) had age matched Z-scores of -1.0 or lower in all three non-mandibular sites (l umbar spine, femoral neck and forearm). Using these patients as the pr oportion of the population with a positive finding of ''low bone mass' ', the sensitivity and specificity of mandibular BMD in predicting low bone mass for these patients was determined. Where a diagnostic thres hold for low mandibular BMD was set at one standard deviation below th e mean, the mandibular body BMD measurement gave high sensitivity (0.8 ) and specificity (0.97), the symphysis BMD low sensitivity (0.4) but a high specificity (0.77), while the ramus BMD had a moderate level of sensitivity (0.6) and high specificity (0.91). It is concluded that m andibular BMD assessed by DXA correlates significantly with BMD measur ements of other important skeletal sites. The higher correlation coeff icients and the greater sensitivity and specificity for the body of ma ndible suggest that this site should be used for any potential clinica l application of dental radiographs in detection of osteoporosis.