Raman spectroscopic studies of CO2 laser-irradiated human dental enamel

While the effects of carbon dioxide (CO2) laser radiation on the physical p roperties of human dental enamel are well characterized, little is known re garding laser-induced chemical changes. In this study, enamel was exposed t o CO2 laser radiation to induce fusion and recrystallization, and the Raman spectra recorded using both dispersive and Fourier-transformed (FT) Raman spectroscopy. Spectra were compared to a heat-treated specimen of hydroxyap atite (HAP) and enamel. Laser irradiation induced chemical changes which di ffered from those induced by heat treatment. Comparing the Raman spectra of lased enamel to HAP and tricalcium phosphate (TCP), it is evident that CO2 laser irradiation of enamel causes the partial conversion of HAP to TCP. T he effect of laser irradiation is not merely a simple local heating effect as previously thought, since simple heating of enamel leads to the formatio n of both TCP and Ca(OH)(2), while laser treatment of enamel results in the formation of TCP but not Ca(OH)(2). (C) 1999 Elsevier Science B.V. All rig hts reserved.