The progressive mineralization pattern of the developing permanent enamel of dog was studied by means of microradiography, polarized light microscopy and ordinary transmitted light microscopy. The mineralization pattern ravealed in microradiograms of undecalcified ground sections were investigatad with the aid of the two-dimensional densitometry by a television image plane scanning system (colour television display system using digital comparator method) and the one-dimensional line scan densitometry using photomultiplier. The present results were compared with the results of the previous investigations by meaus of micoradiography and tetracycline labelling (Suga, 1969).During the stage of matrix formation, the enamel matrix is mineralized slightly immediately after it was laid down. When the matrix formation is completed, the mineralization degree of the inner-half of layer is little higher than that of the outer-half. On the other hand, the narrow inner-most layer (about 6-8 micron in width) adjacent to the amelodentinal junction is very highly mineralized immediately after the matrix formation commenced (Fig.1-1).When the maturation stage begins (soon after the comlpetion of matrix formation), a secondary heavy mineralization takes place throughout all the layers of enamel matrix. However, the pattern and gradient of mineralization increase, the time of completion of mineralization and the final mineralization degree are different for each layer of enamel, namely, the outer, the middle, the inner and the inner-most layers (Fig.2). During the early stage of maturation, the steepest increase of mineralization degree appeares, at first, in the inner layer, then, in the middle layer. On the other hand, the outer layer increases its mineralization degree with the slowest gradient, therefore, it is easily distinguished from the middle layer (Figs.1, 2 and 3). As it moves to the middle stage of maturation, the mineralization increase at the inner and inner-most layers becomes slower and finally appeares to cease, however, the middle layer still continues its steep mineralization increase and the outer layer shows very slow increase.As it enters into the late stage of maturation, the outer layer begins to mineralize very quickly and, finally becomes to show the highest mineralization degree for the whole layer of enamel (Fig.3). In the present investigation, the contour map representation of mincroradiogram played a very important rôle for recognizing the progressive mineralization pattern mentioned above (Figs.4-7 and 12, a and b).According to both of microradiography and polarized light microscopy, it was observed that the inner-most layer does not increase its width during the whole stage of maturation (Figs.1-3 and 9-11)
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Open Access
Jan 1, 1994
Toshiko Tanaka 
