The effect of curing lights and modes on dentin bond strength of bulk-fill composites applied in different thickness

To investigate shear bond strength (SBS) to dentin of a conventional and three bulk-fill composites applied in different increment thickness and cured by mono- and multi-wave LED LCUs. Two hundred and fifty-two extracted sound human molars were prepared for SBS test. The teeth were divided into four groups according to the resin composites used. Conventional composite: Tetric N-Ceram (control); high-viscosity bulk-fills: Tetric N-Ceram Bulk Fill, X-tra Fil, and SonicFill. Each group was subdivided (n?=?7) according to increment thickness (2, 4, and 6?mm) and cured by standard mode of a mono-wave LED or two different modes (standard and xtra power) of a multi-wave LED. The failure mode was stereomicroscopically determined at 40× magnification. Data were analyzed using Three-way ANOVA and further comparisons were assessed by Bonferroni’s multiple comparison test. There were no significant differences within X-tra fil and Tetric N-Ceram Bulk Fill groups for any of the variables (p?>?0.05). A significant decrease in SBS values with increase of layer thickness was observed for SonicFill and control groups. Also, curing mode had a significant effect on both composites at 6?mm thickness and standard mode of multi-wave LED caused the highest SBS value (p???0.05). Adhesive failure was the most common fracture pattern especially at 6?mm thickness applications. Based on the results of this study, the bulk-fill composites can be safely applied in one-step with 4?mm increments, although the examined composites performed better at 2?mm thickness. The performance of the composites at 6?mm increment may show differences related to the curing lights and modes.