Previously, we reported a moderate correlation between the Vickers hardness number (Hv) and the P concentration, but no correlation with the Ca concentration in sound human enamel. From such a previous study and other studies of sound human dentin on Hv and mineral content, the correlation may not be estimated. In this study, we investigated the correlation by using Vickers microhardness tests and energy-dispersive X-ray microanalysis, and found a relatively high correlation between the Hv and the Ca concentration (r=0.872), and also a relatively high correlation with the P concentration (r=0.876) in the dentin including the outer and middle layers. These data may be based on the dentin matrix possessing higher amounts of organic substance than the hypercalcified enamel. In addition, the relative variances of the Ca and P concentrations between the outer and the middle dentin layer were larger than their concentrations between the inner and the outer enamel layer reported previously, and were similar to the Hv variance in the dentin compared with that in the enamel. Thus, the Hv will reflect a relative mineral content in the sound dentin.
This study was investigated whether bone regeneration is improved in the healing of experimental osseous defects with subperiosteal membranes. Muscle/periosteal flaps were raised, and 4.5-mm osseous defects were created bilaterally in the tibiae of ten rabbits. On the test side, a silicone membrane was placed over the defect, and the flaps were sutured outside the membrane. The defect on the contralateral side served as a control (no membrane). After healing periods of 1, 2, 4 and 8 weeks the animals were killed, and 15μm hematoxylin-eosin-stained, undecalcified sections were prepared and examined histologically. The results suggest that the subperiosteal membrane keeps the osteogenic tissue structurally stable so that osteogenesis remains functionally stable during the early stages of healing.