Effect of Preheating of Resin Composite on Microtensile Bond Strength In Vitro Study

BACKGROUND: Preheating resin composite was one of the latest achievements to improve the mechanical properties of composite. AIM: This study was conducted to assess the effect of preheating of resin composite on microtensile bond strength to dentin. METHODS AND MATERIALS: A total of 32 human molars were selected and divided into two groups according to the type of resin composites either microhybrid (P60) (R1) or nanohybrid (Z250 XT) (R2). The molar teeth were embedded in acrylic resin blocks then the occlusal enamel was removed parallel to cementoenamel junction to expose the dentin. Each group was subdivided into four subgroups according to the number of preheating cycles of resin composite either no heating (C0), one preheating cycle at 68℃ (C1), two preheating cycles at 68℃ (C2), or three preheating cycles at 68℃ (C3). After bonding of resin composite, specimens were cut into beams 1 mm thick and stressed in tension using a universal testing machine (4 teeth per group/12 beams per tooth). STATISTICAL ANALYSIS USED: Two-way ANOVA and Tukey’s post hoc tests were used to test the effect of preheating resin composites for the interaction of different variables. RESULTS: In both variables of the study, the type of resin composite and the number of preheating cycles have a statistically significant effect on the microtensile bond strength to dentin. There was a significant interaction between the variables. CONCLUSION: Pre-heating of Filtek P60 as a packable composite at 68℃ can achieve significantly higher microtensile bond strength compared to Filtek Z250 as a microhybrid composite. Key Messages: Preheating of resin composite enhances the mechanical properties of resin composite. Furthermore, better adaptation is due to easily flow of the material in additional to the improvement of microtensile bond strength of resin composite due to monomer and radical mobility due to complete polymerization during preheating.