Effect of Pre-heating on Microtensile Bond Strength of Composite Resin to Dentin

To evaluate the composite-to-dentin microtensile bond strength after different pre-curing temperatures of two composite resin.The occlusal surface of forty four human molars were abraded with water cooled diamond burs and polished with 600 grit silicon carbide sand papers to obtain flat dentin surfaces.The dentinwas etched with37% phosphoric acid and bonded with Adper single bond2according to manufacturer''s instructions.The specimens were randomly divided into two groups(n=22) according to the composite resin applied;FiltekP60 and Filtek Z250. For each group, three subgroups of composite resin pre-curing temperatures (4, 23, 37) were created. Composite resins were applied and cured on the dentin surface in a plastic mold (8mm in diameter × 4mm in length)incrementally.22 composite-to-dentinhour-glasssticks with 1mm2 cross-sectional area per group wereprepared. Microtensile bond strength measurements were performed using a universal testing machine at 1 cross head speed.For statistical analysis, T-Test and Two-way ANOVA tests were used. The level of significance was set at P<0/05.The FiltekP60 pre-heated in 37ºC had significantly higher microtensile bond strength than Filtek Z250 in same condition. There were no significant different micotensile bond strength values between 4ºC, 23ºC and 37ºC subgroups from each composite resin group.Comparing the two resin composites tested in same pre-cuing temperatures had no significant different values in 4ºC and 23ºC but significant higher value was observed for Filtek P60 at 37ºC.