A study of the internal structure of the Japanese mandible

The thickness of the substantia compacta and the volume and width of the trabecular bone of the substantia spongiosa were investigated by soft X-ray photographs made of thin sections of many kinds of dentulous and edentulous mandibles. The results were: 1) The thickness of substantia compacta is especially thick on the lingual side in the incisor region and thickest in the molar region in all materials. At the base of mandible, the thickness is essentially the same in all regions, but, the thickness of dentulous materials is greater than of edentulous ones. 2) On the upper part, the volume of trabecular bone is less in the premolar region in both edentulous and dentulous material than in other regions, however, there is relative more in edentulous than in dentulous. In the central part, there is almost the same amount of trabecular bone in the dentulous and edentulous material. 3) The width of the trabecular bone in the substantia spongiosa is greater in the incisor region than in other regions in all materials. In the upper and central part, it is smaller in the premolar region in both edentulous and dentulous material but, it increases in the molar region in the edentulous materials.