RESUMO
Together with the controversy which exists in the efficacy of new PAC light curing units, this study evaluated the irradiation effect of plasma ARC and halogen light curing units on the microhardness of three resin composites. In this experimental study, two light - curing units including Remecure CL 15 [PAC] [with the output of 1600 mW/cm[2]] and Arialux [QTH] [with the output of 710 mW/cm[2]] were used. Six specimens of three type of resin composite were prepared in a steel mold with 2mm thickness. The three composites were CeramX [Dentsply], Heliomolar [Vivadent] and Z100 [3M]. Curing time with Remecure was 5 seconds and with Arialux was as the composite manufacturer recommended. After 24 hours, vickers hardness measurements on top and bottom surfaces of each specimen were made and the bottom/top vickers hardness [B/T VHN] was determined. Microhardness of two surfaces in each group was compared by t, 2-way ANOVA and Tukey tests. For Ceramx composite two light curing units showed the same microhardness on the top and bottom surfaces. Heliomolar showed significantly lower values of microhardness on both surfaces and B/T VHN with Remecure. In Z100 specimens microhardness [on both surfaces] was lower with Remecure but B/T VHN was the same [P<0.05]. Except Heliomolar specimens which were cured by Remecure, B/T VHN was acceptable in all groups [more than 80%].The efficiency of Remecure unit in manufacturers' instruction time was equivalent or lower than conventional halogen light depending on the type of resin composite