Abstract
Recently The laser has been applied to numerous dental clinical fields such for treatment of hard and soft tissue diseases. The mechanism of the laser action on dental hard tissues, however, is unclear. The aim of this study was to investigate alterations of the inorganic crystals of human deciduous enamel with CO2 laser irradiation using a polarizing microscope and a Micro X-ray diffraction. Based on observation of the polarizing microscope, several half-circular layers were found around the central irradiated regions while the interference colors of the central regions and the several layers showed grey-white, dark brown, orange, yellow and blue, respectively. Based on analysis of the altered regions using Micro X-ray diffraction, it was found that the enamel crystals [HAP: Ca10(PO4)6(OH)2]were altered as follows. At the irradiated central regions, high temperature phases such as α-Ca3(PO4)2 and semi-high temperature phases such as β-Ca3(PO4)2, α-,β- and γ- Ca2P2O7 were identifled. In the surrounding layers, there were gradual changes from high temperature phases to semi-high temperature phases, and to the normal HAP. It was confirmed also that the altered regions correspond to those observed using the polarizing microscope.
