The Effects of different recycling methods on the shear bond strength of ceramic brackets

Objective: This study aimed to evaluate the effect of different recycling (also known as reconditioning) methods on the shear bond strength (SBS) of ceramic brackets.Methods: Fifty mechanically retentive polycrystalline ceramic brackets and ۵۰ mandibular bicuspids were used in this study. The teeth were divided into ۵ groups and bonded with new (group ۱) or reconditioned brackets. The reconditioning methods were sandblasting (group ۲), sandblasting + silane (group ۳), hydrofluoric (HF) acid + silane (group ۴), and Er:YAG laser (group ۵). The SBS of brackets were assessed and the adhesive remnant index (ARI) scores were determined. Statistical analysis was performed using one-way ANOVA, Tukey, and chi-square tests at P<۰.۰۵.Results: The highest SBS value was observed in brackets treated with sandblasting + silane (۱۹.۲۶ ± ۳.۳۰ MPa), which was comparable to both the control (۱۹.۰۱ ± ۳.۱۲ MPa) and sandblasting (۱۶.۹۸ ± ۳.۱۳ MPa) groups. Treatment with hydrofluoric acid + silane (۹.۴۶ ± ۳.۴۳ MPa) and Er:YAG laser (۹.۷۱ ± ۱.۲۳ MPa) yielded significantly lower SBS values than the other study groups (P<۰.۰۵). The highest overall ARI scores were observed in the HF acid + silane and Er:YAG laser group, indicating more adhesive remnants on the enamel surface.Conclusions: Sandblasting, with or without silane treatment, effectively restored the bond strength of ceramic brackets to almost initial values. Although recycling with hydrofluoric acid + silane or Er:YAG laser produced lower bond strengths, they still surpassed the clinical threshold of ۷.۸ MPa, making them viable options for bracket reconditioning in clinical settings.