Computer Simulation on the Amelogenesis: Three-dimensional Relationship between the enamel structure and Ameloblasts.

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The structural and embryological relationships between ameloblasts and crystallite arrangement were studied on the tooth germ in dog and cat. Under the scanning electron microscope, the three dimensional structure of the Tomes' processes can be envisaged as the upper part of a diagonally cut column. Each of them is constructed by two crescent faces. One is generally flat (S-face) and the other is curved (N-face). The S-face faces to the forming end of the prism and the N-face to the adjacent prism or the interprismatic substances.The crystallites arrange perpendicularly to the S-face and the free surface of ameloblasts which is the area among Tomes' processes and is adjacent to the forming surface of developing enamel. The N-face is only the sliding face of the Tomes' processes.In dog, the structural change of Tomes' processes during amelogenesis were studied by SEM and TEM. Most of processes has the form envisaged as the upper part of a diagonally cut column, but processes forming outer layer of enamel appear the stump-like structure in three dimension. It was concluded from these observations and discussions as follwed. The contour and surface structure of the S-face decides the cross-sectional structure of a prism and the crystallite arrangement pattern in an enamel respectively. And the arrangement of Tomes' processes decides the prism pattern in the enamel. Crystallite arranged on the S-face form the enamel prism, and those on the free surface of ameloblasts form the interprismatic substance.These results were examined by the computer simulation. The displayed crystallite arrangements after simulation represented the same crystallite attangementpattern seen in the natural enamel. The relationships between ameloblasts and enamel structure proposed by us were objectively confirmed.