Mohadese Shokripour
Bahareh Asgartooran
Sharareh Ghasemi
Farnaz Sepehrnia

Background: Adhesion of composite resins to dentin is crucial in restorative dentistry. The aim of this study was to evaluate shear bond strength of composite restorations to dentin under different cycling conditions. Methods: Ninety extracted premolar teeth were randomly divided into ۹ groups (n=۱۰). The samples were mounted in resin and sectioned to prepare dentin samples. Then the samples were polished with ۶۰۰-grit silicon carbide sanding sheet, and adhesive types of bonding (۵th generation/Ambar, ۶th generation/Clearfil SE bond, ۸th generation/G-Premio) were applied on them. Afterward, composite resin was bonded to the surface, and cycling was exerted (control: no cycling; thermal cycling: ۳۰۰۰ cycles, ۵°C to ۵۵°C; thermal/erosive cycling: thermal cycling and storage in hydrochloric acid, pH = ۲.۱, ۵ minutes, ۶ times a day, for ۸ days). Shear bond test was done for the specimens. Finally, statistical analysis was done using a two-way analysis of variance (ANOVA) and Tukey test (P<۰.۰۰۱). Results: G-Premio displayed the most bond strength. No significant differences were observed between Clearfil liner bond and Ambar bond. While significant differences were observed in different cycling conditions. Measured bond strength was reduced by thermal/erosive cycling. Conclusions: Thermal cycling and thermal/erosive cycling could affect the shear bond strength of composite to dentin. Universal bonding systems can also increase the shear bond strength of composite resin to dentin.