Comparative study on the formation of biominerals in enamel and enameloid

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The enameloid covering the surface of the teeth in bony fishes exhibits a very high degree of mineralization, and seems to have functions similar to the enamel in mammals. The dental epithelial cells constituting enamel organs during the enameloid formation stages in rayfinned fishes were observed by transmission electron microscopy and enzyme cytochemistry, which detects hydrolytic enzyme activities. During the mineralization and maturation stages, infoldings of the distal plasma membrane in the inner dental epithelial (IDE) cells were marked, and many mitochondria and acid phosphatase positive lysosomes were present in the cytoplasm. The activities of non-specific alkaline phosphatase, calcium-dependent adenosine triphosphatase and potassium-dependent p-nitrophenylphosphatase were usually detected at the plasma membrane of the IDE cells during the mineralization and maturation stages. These results suggest that the dental epithelial cells are mainly involved in the degeneration and r … More emoval of enameloid matrix and in material transportation during the enameloid mineralization and maturation stages, and that these functions are very important to make large crystals in enameloid.Collar enamel, as well as cap enameloid, is found in the jaw teeth of Lepi sosteus and Polypterus. This means that we can observe amelogenesis following cap enameloid formation during tooth development. In this study, light and electron microscopic immunohistochemistry using antibodies specific to the C-terminal, central and N-terminal regions, respectively, of porcine amelogenin was performed to examine the collar enamel matrices. The enamel matrices showed intense immunoreactions to the C-terminal and central region-specific antibodies. The data suggest that the enamel matrix in bony fishes contains a domain that closely resembles the C-terminal and central regions of porcine amelogenin. The size of crystals in collar enamel was not so large in comparison with that in enameloid. Less absorptive function of the dental epithelial cells on the collar enamel might cause the difference between enamel and enameloid. Less