Effects of Er, Cr: YSGG Laser on Shear Bond Strength of the Orthodontic Brackets for 5 and 10 Seconds: An In Vitro Study.

Objectives: The study designed to compare the effect of erbium, chromium: yttrium-scandium-gallium-garnet (Er, Cr: YSGG) laser at different power outputs and short periods of time (5 and 10 s) and acid etching on the shear bond strength (SBS) and failure mode of metallic orthodontic brackets. . A total of sixty-nine human premolars extracted for orthodontic purposes were used. 60 teeth were randomly assigned to one of the five treatment groups. ( = 12): group 1: 37% phosphoric acid etching and groups 2-5: the enamel surface irradiated by the Er, Cr: YSGG laser operated at different power outputs (1 W, 1.5 W, 2 W, and 2.5 W), each laser group was divided into two subgroups ( = 6) according to exposure time (5 s and 10 s). Nine teeth were not subjected to SBS testing but were prepared for scanning electron microscopy (SEM). The nonparametric Kruskal-Wallis test was used to evaluate the data; the SBS and adhesive remanent index (ADI) were evaluated.

Results: The mean SBS for all laser groups and the acid-etched group were comparable, with no significant differences except for the 1 W group for 5 and 10 s and the 1.5 W group for 5 s. For the ARI scores, no statistically significant difference was found among the groups (=0.059), and the majority of the samples had ARI type 2 or 3.

Conclusion: The laser irradiation at 2 and 2.5 W for 5 s was similar to that produced by acid etching, whereas the laser irradiation at 2 and 2.5 W at 10 s was higher compared with that obtained with acid etching and adequate to etch the enamel.