Effects of different treatments on repair bond strengths of resin-composites

Objectives: The aim of this study was to simulate repair of resin composite (RC) restorations by evaluating the composite-to-composite bond strength after using different combinations of surface treatments. Methods: Eighty-four truncated cones of Filtek Z350 (3M ESPE) were prepared and thermocycled for 500 cycles (5/55°C). The surface of the smaller base of truncated cone was roughened with a 0.5 mm diameter diamond bur. The RC cones were divided into 7 groups according to type of surface treatment on the smaller base: Group 1 – Prime&Bond 2.1; Group 2 – sandblasting with aluminum oxide + Prime&Bond 2.1; Group 3 - laser Er:YAG 60mJ/4Hz + Prime&Bond 2.1; Group 4 -10% hydrofluoric acid + silane; Group 5: silane; Group 6 – self-polymerized acrylic monomer; Group 7: Adper Scotchbond SE. For each group, simulated composite repair was performed after the respective surface treatment with Filtek Z350 using an incremental technique. The specimens were subjected to tensile testing until failure (Emic DL 2000). Data were analyzed by one-way ANOVA and Tukey multiple comparison test at a = 0.05. Results: Composite repair strengths (mean±SD in MPa; N=12) were in descending order: Group 2 – 18.8±4.7^a, Group 1 – 18.7±4.6^a, Group 6 – 13.4±4.9^a,b, Group 7 – 9.5±4.6^b,c, Group 3 – 7.5±3.5^b,c,d, Group 4 – 5.2±6.1^c,d and Group 5 – 2.6±2.3^d. Groups with the same lower case letter superscripts were not significantly different (p> 0.05). Groups 1 and 2 exhibited significantly higher bond strengths than groups 3, 4, 5, 6 and 7. Group 5 showed the lowest bond strength. Conclusion: Within the limits of the present study, the use of Prime&Bond 2.1 with or without sandblasting with aluminum oxide appeared to achieve the best composite repair results. Supported-FAPESP (process 2007/59496-4)