Physico-chemical changes of human enamel irradiated with ArF excimer laser

Background and Objectives: Irradiation of tooth enamel by lasers can alter its structure and chemical composition. The purpose of this work was to determine the compositional changes and to elucidate the mechanisms of laser-enamel interaction using ArF excimer laser. Study Design/Materials and Methods: Human enamel irradiated with ArF excimer laser (wavelength, 193 nm) at different fluences, was examined using X-ray diffraction, infrared (IR) spectroscopy and microprobe analysis. Results: Ablation without significant compositional changes in irradiated enamel was evident when low fluences (∼200-380 mJ/cm²) were used. However, fluences between 640 and 2,300 mJ/cm² resulted in an increased Ca/P ratio, decreased amount of carbonate and protein, and the formation of tricalcium phosphate and tetracalcium phosphate, suggesting the involvement of a photothermal mechanism. Conclusions: The results show that ArF excimer laser can alter the chemical composition and morphology of the highly mineralized (96%) dental enamel, depending on the fluence used.