Effects of Laser Etching on Shear Bond Strengths of Brackets Bonded to Fluorosed Enamel

Abstract

Aim: To evaluate the effects of laser etching on the shear bond strengths (SBS) and failure modes of brackets bonded to fluorosed enamel. Materials and Methods: This in vitro study included 34 fluorosed and 34 nonfluorosed teeth. Teeth were divided into four subgroups according to the etching procedure: Group (A) normal enamel etched with 37% phosphoric acid for 15 s, Group (B) nonfluorosed enamel etched with erbium:yttrium aluminum garnet (Er: YAG) laser for 15 s, Group (C) fluorosed enamel etched with 37% phosphoric acid for 30 s, Group (D) fluorosed enamel etched with Er: YAG laser for 30 s. After bonding of the premolar metal brackets, specimens were subjected to the thermal cycles. After SBS test, modified adhesive remnant index (ARI) by using stereomicroscope and failure modes with a scanning electron microscope (SEM) was determined. After bonding, one specimen from each group was examined under SEM to identify enamel-resin interfaces. ANOVA and Tukey post-hoc tests were used to compare the SBS values. The KruskaluWallis and Chi-square tests were used to analyze the distribution of ARI scores and failure modes of groups. Results: The highest mean SBS value (17.56 +/- 1.05 MPa) was found in Group A, while the lowest (12.25 +/- 0.96 MPa) in Group D. Significant differences were found in the SBS test and failure modes among all groups. The differences between ARI scores of the groups were not significant. Conclusion: According to our findings, laser etching reduced the SBS of brackets bonded to fluorosed teeth, but provided clinically acceptable SBS values.