Influence of Acidic Erosion on Enamel Bond Strength of Universal Adhesive

<p> Purpose: This study examined the bonding performance of universal adhesives to acid eroded enamel substrates.</p><p> Methods: Three universal adhesives were used: All-Bond Universal (AB), Adhese Universal (AU), and Scotchbond Universal Adhesive (SB). Bovine incisors were sectioned to expose the flattened enamel area, and ground wet with #600-grit SiC paper. One group of ten specimens was treated with citric acid solution (pH 2.1) five times for one min (Er group) twice a day. These procedures were done throughout the 7-day test period (7-day group). Before applying adhesives, adherent enamel surfaces were treated with or without phosphoric acid. Then, universal adhesive was applied and light cured, and resin composite was condensed into a mold and polymerized. Ten samples per test group were stored in distilled water at 37°C for 24 h, and further specimens were subjected to thermal cycling (TC) for 10,000 or 30,000 times, then bond strengths were measured with a crosshead speed of 1.0 mm/min.</p><p> Results: The results of the enamel bond strengths of the Er group showed no significant differences compared to the control group. On the other hand, compared to the control group, bond strengths were significantly higher in all groups except SB without phosphoric acid etching in the 7-day group, and in AB and SB with phosphoric acid etching and AU without phosphoric acid etching in the immediate group. After thermal cycling, there were no significant differences between with etching and without etching groups for all the materials tested.</p><p> Conclusion: Within the limitations of this in vitro study, it can be concluded that the acidic erosion of enamel substrate affected the bonding performance of universal adhesives. Enamel bond strength increased when phosphoric acid was employed, and stable enamel bond strength was obtained after thermal cycling.</p>