[in Japanese]

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[in Japanese]

View full abstract

[in Japanese]

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[in Japanese]

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1) Progressive mineralization patterns of the developing enamel of golden hamster incisor were studied by means of microradiography and tetracycline labelling. The mineralization patterns revealed in microradiograms of non-decalcified longitudinal ground sections were investigated with the aid of two-dimensional densitometry by a television image plane scanning system (colour data system using the digital comparator method)(Fig. 3). Some animals injected with tetracycline were sacrificed, from 4 hrs. to 2 days after the injection. Tetracycline labelling patterns were photographed with a fluorescence microscope (Figs. 4 and 5).
2) During the stage of matrix formation, the organic matrix mineralizes slightly immediately after it is laid down by the ameloblasts, but its mineralization degree (except the very narrow layer along the amelodentinal junction) is lower than that of dentin (Fig. 2-1 and Fig. 3-1).
3) When the maturation stage begins (soon after the completion of matrix formation), a secondary increase of mineralization degree takes place throughout all the layers of enamel (Figs. 2 and 3). The gradient of mineralization increase, the time of completion of mineralization and the final mineralization degree are different remarkably for each layer in the enamel, namely, the outermost layer, the outer layer, the middle layer, the inner layer and the innermost layer (Fig. 7).
During the early and middle stages of maturation, the middle layer shows the steepest increase of mineralization degree (Fig. 2-2-4, and Fig. 3-2-4) and consequently the earliest competion of mineralization (Figs. 4 and 5). On the other hand, the outer layer increases its mineralization degree in the most slow gradient for all the layers (Fig. 2-2-4, and Fig. 3-2-4), but, when the late stage of maturation bigins, its gradient of mineralization increase becomes very steep (Fig. 2-5-7, and Fig. 3-5-7) and completes mineralization last the whole layer (Figs. 4 and 5).
The mineralization degree of the fully matured enamel is highest in the outermost and outer layers and it decreases gradually towards the amelodentinal junction (Fig. 2-7, 8, and Fig. 3-7).
4) Tetracycline labelling patterns indicate that the mineralization of the outer layer takes 4 times, the middle layer about 3 times and the inner and the innermost layers about 3.3 times, as the formation of the whole width of matrix of that portion (Fig. 4).
5) By the comparison between the fluorescence microgram and the ordinary light microgram obtained from the same ground section, it is noticed that the deposition of iron-containing substance into the surface layer of enamel from the ameloblasts occurs soon after the mineralization in the outer layer has been completed (Fig. 6).

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