Shear bond strength of orthodontic brackets to fluorosed enamel

Abstract Objectives To evaluate the influence of dental fluorosis and etching time on the shear bond strengths (SBSs) of orthodontic brackets to human enamel. Methods A total of 48 human maxillary central incisors, extracted for periodontal reasons were used. The sample was divided into three experimental groups ( n  = 16): group H30 with healthy teeth and group F30 and F60 with fluorosed teeth (Thylstrup and Fejerskov Index scores 3–4). After etching the dental enamel with 35% phosphoric acid for 30 s (groups H30 and F30) or for 60 s (group F60), metal orthodontic brackets were bonded with Transbond XT adhesive system and light cured (1200 mW/cm 2 for 10 s). The specimens were then thermocycled (5–55 °C, 500 cycles), stored in distilled water (37 °C/7 days), and tested in shear (Instron, 1KN, 1 mm/min). Failure mode was classified, with a stereomicroscope (20× magnification), according to the adhesive remnant index (ARI). SBS data were statistically analyzed with 1‐way ANOVA, followed by Tukey post hoc tests ( α  = 0.05). Kruskal–Wallis and Mann–Whitney nonparametric tests were used to analyze failure data ( α  = 0.05). Results No statistically significant ( p  = 0.763) differences were found between F30 and F60, but these groups showed a statistically ( p p Conclusion Orthodontic brackets adhesion to enamel is negatively influenced by dental fluorosis. Doubling the etching time in fluorosed teeth was not enough to produce similar results to those observed in the healthy ones.