PNNL

Abstract

We observed x-ray linear dichroism in various apatite crystals, including geologic hydroxyapatite (Ca5(PO4)3OH), fluorapatite (Ca5(PO4)3F), and their biogenic counterparts in parrotfish bone, dentin, and enameloid, the fish equivalent of dental enamel. This discovery is important because it now enables visualization of the nano- to micro-scale structure of apatite crystals in human teeth and bone. Illustrative new maps of parrotfish enameloid show a most complex arrangement of fluorapatite crystals, bundled and interwoven, which makes parrotfish enameloid uniquely capable of biting stony corals.