[Anatomical and histological studies on a microdontic wisdom tooth].

The purpose of this study is to investigate features and histological structures of the microdontic wisdom tooth. Materials investigated in this study deal with a very small upper right microdontic wisdom tooth of a male patient aged thirty-six. It was observed with binocular microscopy and under X-ray. Horizontal ground sections of it were prepared and observed with polarizing microscopy, phase microscopy, microradiograph, and scanning electron microscopy. Total length of this specimen was about 1/2 of the average measurement in Japanese upper third molars, breadth of the crown about 1/3, thickness of the crown about 1/4. It had one cusp and one root. It is considered that one cusp was formed by fusing of the mesiolingual cusp and mesiobuccal one because fundamental features of the buccal and lingual surfaces of upper molars were preserved in this specimen. It is thought that dental tubules in this specimen were formed more densely than those in the common wisdom tooth because the space of retreating odontoblasts of this specimen was limited but that enamel rods in this specimen were formed more thickly than those in the common wisdom tooth because the space of retreating ameloblasts of this specimen was wide. It is considered that the degeneration in this specimen came up to not only the dental form, but also the histological structure of the enamel because the surface layer of the enamel of this specimen was composed of the laminal structure.