Raman Analyses of Laser Irradiation-Induced Microstructural Variations in Synthetic Hydroxyapatite and Human Teeth

The microstructural and molecular-scale variations induced by laser irradiation treatment on human teeth enamel in comparison with synthetic hydroxyapatite (HAp) were examined through Raman microprobe spectroscopy as a function of irradiation power. The results demonstrated that laser irradiation could modify stoichiometry, microstructure, and the population of crystallographic defects, as well as the hardness of the materials. These modifications showed strong dependences on both laser power and initial nonstoichiometric structure (defective content of HPO₄), because of the occurrence of distinct reactions and structural reconstruction. The reported observations can redirect future trends in tooth whitening by laser treatment and the production of HAp coatings because of the important role of stoichiometric defects.