Shear bond strength of one-step self-etch adhesives to enamel: effect of acid pretreatment

Aim: The purposes of this study were to evaluate the effect of surface pretreatment with phosphoric acid on the enamel bond strength of four-one-step self-etch adhesives with different pH values. Material and methods: One hundred bovine permanent mandibular incisors were used. The materials used in this study included four-one-step self-etch adhesives with different pH values: Adper (TM) Easy Bond Self-Etch Adhesive (ph = 0,8-1), Futurabond NR (ph = 1,4), G-aenial Bond (ph = 1,5), Clearfil 3 S Bond (ph = 2,7). One two-step self-etch adhesive (Clearfil SE Bond/ph = 0,8-1) was used as control. The teeth were assigned into two subgroups according to bonding procedure. In the first subgroup (n = 50), no pretreatment agent was applied. In the second subgroup (n = 50), etching was performed using 37% phosphoric acid for 30 s. After adhesive systems application, a nanohybrid composite resin was inserted into the enamel surface. The specimens were placed in a universal testing machine (Model 3343, Instron Corp., Canton, Mass., USA). After the testing procedure, the fractured surfaces were examined with an optical microscope at a magnification of 109 to determine failure modes. The adhesive remnant index (ARI) was used to assess the amount of adhesive left on the enamel surface. Results: Descriptive statistics of the shear bond strength and frequency distribution of ARI scores were calculated. Conclusions: Enamel pretreatment with phosphoric acid significantly increased bond strength values of all the adhesives tested. No significant differences in bond strength were detected among the four different one-step self-etch adhesives with different pH. Two-step self-etch adhesive showed the highest bond strength.