In vitro study of the Nd : YAG laser effect on human dental enamel: Optical and scanning electron microscope analysis

Objective: The Nd:YAG laser irradiation of dental enamel was evaluated in e namel demineralization experiments in a Streptococcus mutans culture media. Summary Background Data: Previous studies had shown that a continuous wave Nd:YAG laser at an energy of approximately 67 mJ may induce an increased a cid resistance in human dental enamel when exposed to severe demineralizati on conditions. Methods: Enamel windows of 3 x 4 cm in the buccal surface we re irradiated with a continuous wave Nd:YAG laser at a wavelength of 1,064 Ecm using energy densities of from 83.75 to 187.50 J/cm(2), Enamel windows of 3 x 4 cm on the lingual surface served as control (without the laser irr adiation). The enamel windows were then exposed to a Streptococcus mutans c ulture media at a temperature of 37 degrees C for 15 and 21 days. The laser effects and demineralization were examined both by optical microscopy and scanning electron microscopy (SEM), Results: A comparison between the lased and the unlased windows of enamel showed fusion and recrystalization of th e enamel and increased acid-resistance in all groups irradiated with the Nd :YAG laser, On the other hand, the 3 x 4 delimited enamel surfaces from the control group (not irradiated with the Nd:YAG laser) showed 100% demineriz ation, Conclusions: These findings are consistent with the finding that las er irradiation of dental results in significant reduction of the effective solubility of enamel mineral.