Variation in the apparent density of human mandibular bone with age and dental status.

This study examines the variability in the anatomy of mandibles of differing ages and different stages of tooth loss. Mandibles from individuals between 19 and 96 y were sectioned into 2 mm thick vertical plane-parallel slices and cleaned of marrow and periosteum. The apparent density (mass per unit volume in g/ml) from midline (MID) and mental foramen region (MF) sites was determined by weighing the slices and dividing by a volume calculated as the product of section thickness and the mean area of the 2 sides of the section. The cortical thickness of the inferior border and the basal and alveolar bone heights were measured in radiographs of the slices. Mandibular apparent density was negatively correlated with the cross sectional area (midline r=-0.48, mental foramen r=-0.45), and at the midline was significantly greater in edentulous than in dentate individuals (means (+/-S.E.M.) edentulous n=13: 1.43 (+/-0.07) g/ml; dentate n=17: 1.27 (+/-0.04) g/ml, P < 0.05). Where a large enough age range was available, mandibular apparent bone density showed a significant increase with age (midline males: r=0.53, n=18) especially for dentate individuals (r=0.91, n=8). There was a correlation between the apparent densities at the two sites in the same mandible (r=0.64), with the values obtained for the midline being significantly greater than for the mental foramen region (midline 1.34 (+/-0.04) g/ml; mental foramen 1.19 (+/-0.04) g/ml, P < 0.001, paired t test). The mandible shows great interindividual variability, but there may be a considerable reduction in cross sectional girth of the mandible following tooth loss, and, unlike postcranial sites, an increase in apparent density with age.