Microshear Bond Strength of Composite to Superficial Dentin by Use of Universal Adhesives with Different pH Values in Self-Etch and Etch & Rinse Modes

Abstract

Background: This study aimed to assess the microshear bond strength (micro-SBS) of two universal adhesives with different pH values in etch-and-rinse (E and R) and self-etch (SE) modes to superficial dentin. Materials and Methods: This in vitro experimental study evaluated 75 extracted sound human third molars. Superficial dentin was exposed by trimming the enamel and removing 0.5-1 mm of tooth structure beyond the dentinoenamel junction. A 600-grit abrasive paper was used to create smear layer. The teeth were randomly divided into five groups (n = 15). All-Bond Universal and G-Premio Bond were applied in E and R and SE modes in four groups. Clearfil SE Bond was used in the control group. Z350XT composite cylinders (0.9 mm diameter and 1.5 mm height) were then bonded to the prepared surface. The teeth were incubated at 37°C and 100% humidity for 24 h. Micro-SBS was measured by a universal testing machine, and the mode of failure was determined under a stereomicroscope. Data were analyzed using ANOVA, Bonferroni test, and Fisher's exact test (alpha = 0.05). Results: The micro-SBS of Clearfil SE Bond was significantly lower than all other groups (P < 0.05). All-Bond Universal yielded the maximum micro-SBS in SE and minimum micro-SBS in E and R mode. All-Bond Universal showed significantly lower micro-SBS in E and R mode than SE mode (P < 0.05). No other significant differences were noted. The mode of failure was also significantly different among the groups (P < 0.05). Mixed failure had the highest frequency in G-Premio in E and R mode. Conclusion: Type of adhesive and application mode affected the micro-shear bond strength to superficial dentin.