A histological, chemical and X-ray diffraction study on contemporary ( Carcharias glaucus) and fossilized ( Macrota odontaspis) shark teeth

Abstract

It is well known that the fluoride content of contemporary shark teeth is nearly as high as that of pure fluorapatite (3.77 per cent). The purpose of this study was to compare the structure and chemical composition of contemporary and fossilized shark teeth (30 million years old). Microradiographical studies revealed that the fossil shark teeth were denser than the contemporary ones. On the basis of chemical analyses and X-ray diffraction studies it is suggested that contemporary shark teeth consist partly of fluorapatite with a small F − component replaced by OH − or H 2O, and partly of amorphous Ca 3(PO 4) 2 or defect apatite with a low Ca:P-ratio. The study supports the hypothesis that the fluoride content in dental hard tissues can increase owing to the diffusion of fluoride from the environment.