Adhesion of and on Er:YAG Laser-Irradiated Dental Enamel: Effect of Surface Roughness.

To determine surface roughness caused by Er:YAG laser irradiation and its effect on the increase in bacterial adhesion. Er:YAG laser was proposed as a strategic device to reduce caries by its ability to generate chemical and structural changes in tooth enamel; in turn, it produces undesirable effects on the tooth surface that could increase its roughness and allow a greater accumulation of microorganisms. Eighty-four samples of human enamel were divided into seven groups ( = 12): G1_control (no laser irradiation); G2_100/HO, G3_200/HO, and G4_300/HO were irradiated with Er:YAG laser (12.7, 25.5, and 38.2 J/cm, respectively) under water irrigation. In addition, G5_100, G6_200, and G7_300 were irradiated with the energy densities described above and no water irrigation. Surface roughness measurements were recorded before and after treatment using a profilometer. Afterward, three samples per group were incubated in a microorganism suspension for the tetrazolium salt (XTT) assay. Biofilm morphology was observed using scanning electron microscopy and confocal laser scanning microscope. One-way analysis of variance and -tests were performed for statistical analysis ( < 0.05). There were no statistically significant differences in roughness values in the G5_100 group before and after treatment, but there were statistically significant differences observed in the other groups evaluated ( < 0.05). No significant differences in adhesion of both strains were detected in irradiated groups compared with G1_control. The increase in roughness on dental enamel surfaces was proportional to the irradiation conditions. However, the increase in surface roughness caused by Er:YAG laser irradiation did not affect and adhesion.