Influence of thermal cycling on dentin bond strength of two-step bonding systems.

PURPOSE: To investigate the influence of thermal cycling on bond strength to dentin of 2-step bonding systems. MATERIALS AND METHODS: The systems used were self-etching primer systems; Fluoro Bond (FB), Liner Bond II (LB), and Mac Bond II (MB); and self-priming adhesive systems; One-Step (OS), OptiBond Solo (OB), Prime & Bond 2.0 (PB), and Single Bond (SB). Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were wet ground with #600 SiC paper. Enamel and dentin surfaces were treated following each manufacturers' instructions. Adhesives were applied and composites were condensed into a Teflon mold (4x2 mm) placed on the dentin surface and light activated. Bonded specimens were divided into four groups; (a) stored in 37 degrees C water for 24 hours, (b) stored in 37 degrees C water for 24 hours followed by subjecting to thermal cycling between 5 degrees C and 60 degrees C for 3,000 times, (c) 10,000 times, and (d) 30,000 times. Twelve samples per test group were shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVAs followed by Duncan's multiple range test (P < 0.05) were performed. RESULTS: For FB, LB, and MB, a small decrease in bond strength was observed and no significant differences were observed among the thermal cycling groups. For OS, OB, PB, and SB, a significant decrease in bond strength was observed for the 30,000 thermal cycling groups. The changes in bond strength after TC were different between the bonding systems.