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Abstract This study investigated the microshear bond strength (MSBS) of two different types of resin composite (nanofilled and microhybrid) as affected by different light intensities, curing modes of light emitting diode and effect of thermocycling. Materials and Methods : Two types of resin composite Filtek Z350 (nanofilled), Filtek Z250 (microhybrid) and adper single bond plus (etch-and-rinse adhesive), were selected. One hundred and sixty human molars were used. The molars were embedded in self cure acrylic resin using specially designed Teflon mold. The enamel was removed till exposure of dentin to prepare a flat surface. The samples were divided into two main groups, 80 teeth each, according to the type of resin composite used each group was further subdivided into two equal subgroups according to the intensity of light, either low or high intensity each subgroup were divided into two divisions according to curing mode, soft-start or snap shot. Half of the samples were stressed for 500 thermocycles. Composite specimens were made using polyethylene tube (2mm hight and 1.2mm internal diameter) (MSBS)was determined in a universal testing machine at a crosshead speed of 0.5mm/min. The results were analyzed with ANOVA and Tukey-post. Hoc test at significant level P £ 0.05. |