エナメロイドのフッ素含量と魚の系統 エナメル質形成機構の進化へのアプローチ

Abstract

The enameloid of fish teeth is analogous to the enamel of mammalian teeth and similary highly mineralized. Quantitative electron microprobe analysis of the teeth of various teleost fishes when considered from the view point of their systematic classification indicates that fishes may be placed into two groups in terms of the fluoride concentration in the enameloid; one group containing fluoride of more than about 2.0% in the enameloid; and the other containing less than about 0.3%(Figs.6 and 8). The fluoride concentration in the enameloid is related to the fish phylogeny rather than to the fluoride concentration in the environmental water (Table 1, Figs.2-8). It is also not related to feeding habits, though the form, size and distribution, of the teeth show a wide range of adaptation in association with feeding habits (Figs.1and5, Table2). It seems to indicate that the evolution of the chemical composition of enameloid is completely independent of morphological adaptation of teeth. Similar phenomena have been found related to the iron concentration in enameloid.Crystallographic investigations indicate that, in the high fluoride enameloid, apparently fluoride is present in the apatite as Ca10 (PO1) e (F, OH) or Ca10 (PO4) 6 F2 (Figs. 9-11).Since the fluoride concentration in the dentin and bone is very low, in contrast the high concentration of fluoride which can be observed even in the developing enameloid, it seems that there is a peculiar mechanism under the control of the ameloblasts which concentrates the fluoride in enameloid.The present investigations seem to provide evidence which could lead to a better understanding of the evolution of the mechanisms of tooth enamel formation (Figs. 12and13).