Evaluating resin-enamel bonds by microshear and microtensile bond strength tests: effects of composite resin

Objectives: The aims of this study were to evaluate the effect of resin composite (Filtek Z250 and Filtek Flow Z350) and adhesive system [(Solobond Plus, Futurabond NR (VOCO) and Adper Single Bond (3M ESPE)] on the microtensile (mu TBS) and microshear bond strength (mu SBS) tests on enamel, and to correlate the bond strength means between them. Material and Methods: Thirty-six extracted human molars were sectioned to obtain two tooth halves: one for mu TBS and the other one for mu SBS. Adhesive systems and resin composites were applied to the enamel ground surfaces and light-cured. After storage (37 degrees C/24 h) specimens were stressed (0.5 mm/min). Fracture modes were analyzed under scanning electron microscopy. The data were analyzed using two-way ANOVA and Tukey's test (alpha=0.05). Results: The correlation between tests was estimated with Pearson's product-moment correlation statistics (alpha=0.05). For both tests only the main factor resin composite was statistically significant (p<0.05). The correlation test detected a positive (r=0.91) and significant (p=0.01) correlation between the tests. Conclusions: The results were more influenced by the resin type than by the adhesives. Both mocrobond tests seem to be positive and linearly correlated and can therefore lead to similar conclusions.