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

This study aimed to evaluate the effect of different recycling (also known as reconditioning) methods on the shear bond strength (SBS) of ceramic brackets. Fifty mechanically retentive polycrystalline ceramic brackets and 50 mandibular bicuspids were used in this study. The teeth were divided into 5 groups and bonded with new (group 1) or reconditioned brackets. The reconditioning methods were sandblasting (group 2), sandblasting + silane (group 3), hydrofluoric (HF) acid + silane (group 4), and Er:YAG laser (group 5). 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<0.05. The highest SBS value was observed in brackets treated with sandblasting + silane (19.26 ± 3.30 MPa), which was comparable to both the control (19.01 ± 3.12 MPa) and sandblasting (16.98 ± 3.13 MPa) groups. Treatment with hydrofluoric acid + silane (9.46 ± 3.43 MPa) and Er:YAG laser (9.71 ± 1.23 MPa) yielded significantly lower SBS values than the other study groups (P<0.05). 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. 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 7.8 MPa, making them viable options for bracket reconditioning in clinical settings.