Adhesion strategy and curing mode of a universal adhesive influence the bonding of dual-cured core build-up resin composite to dentin

To evaluate the influence of different adhesion strategies and curing modes of a universal adhesive on shear bond strength (SBS) of a dual-cured core build-up resin composite to bovine dentin. In total, 60 bovine anterior permanent teeth were randomly divided into 6 groups (n = 10/group) according to; 1: Adhesion strategy, 3 groups (self-etching, etch-and-rinse/wet and etch-and-rinse/dry) and 2: Curing mode, 2 groups (light-curing and dual-curing). Subsequent to root and incisal half removal of each tooth, labial enamel was wet ground over #180 SiC papers, and exposed dentin surface was wet ground over #600 SiC paper for 60 s to create a standardized smear layer. Universal adhesive was applied according to its manufacturer instructions and each tooth was then restored with one dual-cured composite cylinder (2mmx2mm). Shear bond strength was run at a crosshead speed of 0.5 mm/min, and failure modes were categorized into: 1- Adhesive, 2- Mixed and 3- Cohesive failures. Statistical analysis was performed using Two-Way ANOVA/Tukey HSD test. The results showed that factor 'adhesion strategy' had no statistically significant effect on SBS (p = 0.525). However, factors 'curing mode' and 'adhesion strategy x curing mode' showed statistically significant effect on SBS (p = 0.020 andp = 0.002 respectively). Mixed failure represented 55%, followed by adhesive failure (43.3%) and the cohesive failure represented 1.7%. It seemed better to apply the universal adhesive used in this study in etch-and-rinse strategy rather than self-etching one, especially when the adhesive was used in light-curing mode. The use of the DC activator seemed to be unnecessary.