SYNOPSIS
The present study was designed to examine the crystal nature of dentin, and the relationship between the crystal orientation and the mechanism of tooth formation among the monophyodont teeth, diphyodont teeth and polyphyodont teeth. The apatite crystal of dentin was studied using the curve IP x-ray Laue system and the laser Raman microprobe spectrometry. The crystal orientation was very poorly orientated in the enamel-covered crown dentin of the diphyodont. In the enamel-covered dentin, calcospherites were present. In the presence of calco-spherites, the crystal orientation was arranged radially. The crystals were orientated indistinctly in the cementum-covered root dentin of the diphyodont. In the cementum-covered dentin, the axis of crystal orientation was almost parallel to the tooth axis and to the direction of the collagen fibers. In the enamel-covered crown dentin from the monophyodont and polyphyodont, the crystal orientation was recognized as similar to the cementum-covered root dentin. In the Raman spectrum of dentin, the peak of 1074cm^-1 (CO₃^2-) in the monophyodont teeth was lower than that of diphyodont teeth. The results suggest that there is a relationship between the mechanism of the tooth formation and the characteristic of dentin crystal. It is considered that the analysis of structural mechanism of the dentin gives much information to the regeneration research.

Key words: dentin crystal, crystal orientation, x-ray diffraction, laser Raman microprobe spectrometry, tooth formation