Mineralization density and apparent density of bone in cranial and postcranial sites in the aging human.

This study addressed the question whether bone density of the mandible reflects bone density at other sites. Samples of cranial bone (mandible and parietal bone) and postcranial bone (fourth lumbar vertebral body, iliac crest and femoral neck) from 14 individuals aged 69-96 years were compared. One slice from each bone was used for apparent density determination by weighing it and dividing by a volume calculated as the product of section thickness and the mean area of the two sides of the section. Another slice was embedded in poly(methylmethacrylate) and micromilled to study the mineralization density by quantitative backscattered electron (QBSE) analysis in a scanning electron microscope, rescaling image histograms to the signal range from a monobrominated (0) to a monoiodinated (255) dimethacrylate resin standard. Mandibular QBSE values (e.g., at the mental foramen region 178.0) were much higher (p < 0.0001, paired t-test) than at other sites (parietal, 170.1; fourth lumbar vertebra (L4), 155.4; iliac crest (IC), 155.2; femoral neck (FN), 160.7 units), and correlated only with parietal bone (r = 0.70). Mean QBSE values for the postcranial sites were correlated (L4 with IC, r = 0.63; L4 with FN, r = 0.88; IC with FN, r = 0.59) as were the apparent density values (L4 with IC, r = 0.87; L4 with FN, r = 0.75; IC with FN, r = 0.80). Neither the apparent density nor the mineralization density of the mandible showed a correlation with values for the postcranial sites. The condition of bone in the elderly mandible should not be used to infer status at postcranial sites.