Crystallographic analysis of demineralized human enamel treated by laser-irradiation or remineralization.

Crystallographic information on dental hard tissue is helpful in evaluating whether incipient caries that has received preventative treatments is resistant to subsequent attack. The aim here was to analyse crystallographically by means of high-resolution electron microscopy (HREM) demineralized human enamel that had been laser-irradiated or remineralized. Electron-microscopic observation identified a distinct layer at a depth of 100 nm in the demineralized and laser-irradiated enamel. The crystallinity in the shallower area was inferior to that in the deeper area. Comparison of the HREM findings from the deeper area with the data provided by the Joint Committee on Powdered Diffraction Standards revealed that the mineral in the demineralized and laser-irradiated enamel was either alpha- or beta-tricalcium phosphate, while that in the remineralized enamel was thought to be tetracalcium diphosphate monoxide.