Impact of surface treatment methods on bond strength of orthodontic brackets to indirect composite provisional restorations

Abstract

Aim: To assess the impact of different surface treatment protocols on the shear bond strength (SBS) of metal orthodontic brackets (MOBs) and ceramic orthodontic brackets (CBOs) bonded to provisional crowns via the SBS test. Materials and methods: A total of 120 provisional indirect composite crowns (SR Nexco; Ivoclar Vivadent) for maxillary first premolars were fabricated and evenly allocated into two groups: MOBs and CBOs. According to the surface treatment protocol, each group was divided into three subgroups: group CO, no treatment; group HF, the surface was etched with 10% hydrofluoric acid; and group SA, the surface was sandblasted followed by silanization. After bracket bonding, the samples were subjected to 3,000 thermocycles between 5°C and 55°C. SBS was evaluated using a universal testing machine at a crosshead speed of 1 mm/minute and the adhesive remnant index (ARI) was identified. For statistical analysis, ANOVA and Tukey HSD post hoc tests were performed. Results: Mean bond strength values for CBOs cemented to control, HF-, and SA-treated subgroups before and after thermocycling were (9.6 ± 1.4, 6.2 ± 1.1), (17.8 ± 2.1, 13.8 ± 1.3), and (17.2 ± 1.4, 12.1 ± 1.8) MPa, respectively. For the metallic brackets, the results were (7.7 ± 2.3, 3.9 ± 1.4), (15.5 ± 1.6, 12.8 ± 1.2), and (15 ± 1.2, 11.2 ± 1.6) MPa, respectively. There was a significant difference (p = 0.000) between ceramic and metallic bracket groups. Conclusion: Conditioning of indirect composite provisional crowns either with HF or SA was significantly affecting the adhesion to both bracket types. Clinical significance: Increasing the bond strength between provisional crowns and orthodontic brackets (OBs) may improve the treatment standard provided to patients.