Objective: This investigation was performed to evaluate the effect of CO2 laser irradiation on the acquired acid resistance of dental hard tissues to artificial caries-like formation and the ultrastructure of lased areas was morphologically investigated in vitro.
Summary background data: In recent years, many studies have been carried out to evaluate the effect of the CO2 laser on the enhanced resistance to artificial caries formation of enamel. However, a limited number of papers concerning its effect on dentin have been published.
Methods: A CO2 laser of 10.6 microns wavelength was used to irradiate human enamel and dentin samples from 20 extracted human molar teeth, and samples were subjected to 2 microliters of 0.1 M lactic acid solution (pH 4.8) for 24 h at 36 degrees C. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometry and the morphological changes were investigated by scanning electron microscopy (SEM).
Results: The lowest mean Ca2+ ppm was recorded in the samples irradiated at 3 W, followed by 2 W, 1 W, and unlased samples. SEM observation showed that the lased areas were melting with solidification of the smear layer. Even after acid demineralization, the lased surfaces were almost unchanged.
Conclusions: The results of this study suggested that CO2 laser irradiation could sufficiently melt and solidify the enamel and dentin surfaces and thus enhance resistance to artificial caries-like formation.