DURABILITY OF ENAMEL BOND STRENGTH OF SIMPLIFIED BONDING SYSTEMS

Abstract

ABSTRACT Objective: The purpose of this study was to determine the effect of thermal cycling on the enamel bond strengths of two‐step adhesive systems, either self‐etching primers or “one‐bottle” total‐etch systems, to bovine enamel. Materials and Methods: Three self‐etching primer systems–Imperva Fluoro Bond® (Shofu Inc., Kyoto, Japan), Clearfil® Liner Bond II (Kuraray Co. Ltd., Osaka, Japan), and Mac Bond® II (Tokuyama Corp., Tokyo, Japan)–and four total‐etch adhesive systems–One‐Step® (Bisco Inc., Schaumburg, IL, USA), Opti‐Bond Solo® (Kerr Corporation, Orange, CA, USA), Prime & Bond® 2.0 (Dentsply DeTrey, Konstanz, Germany), and Single BondTM (3M ESPE, St. Paul, MN, USA)–were used. Labial enamel surfaces of bovine incisors were exposed by grinding with 240‐grit and 600‐grit wet silicon carbide paper. Enamel was treated according to the manufacturers' instructions. Following the application of adhesive resin, resin composites were condensed into a mold (diameter = 4 mm, depth = 2 mm) and were light‐cured. Bonded specimens were stored in 37°C water for 24 hours. They were divided into a control group (no thermal cycling) and three experimental groups with thermal cycles of 3,000, 10,000, and 30,000 cycles, respectively, between 5°C and 60°C. The shear test was performed at a crosshead speed of 1.0 mm/min. The ultrastructure of resin‐enamel interfaces was observed by SEM at times 3,500 magnification. Results: Self‐etching primer systems had significant decreases in enamel bond strengths with thermal cycling. In contrast, total‐etch systems had no significant differences, except for One‐Step. Mixed failures were predominant in these systems, but adhesive failures tended to increase with a greater number of thermal cycles. SEM observations revealed small cracks at the resin‐enamel interface for self‐etching primer systems when subjected to 30,000 thermal cycles. Conclusions: Enamel shear bond strengths after thermal cycling of self‐etching primer systems appeared to be less stable than were those of total‐etch adhesive systems.