Different light sources and curing distances are considered to be the 2 most-important factors influencing the physical properties of light-cured resin composites. The purpose of this study was to evaluate the surface microhardness of resin composites cured with 2 different light curing units (LCUs) at 4 different curing distances. Forty-eight samples of resin composite(shade A3.5) were randomly divided into8groups each with 6 samples. The groups were individually subjected to 8 different curing conditions, and were cured for 40 s. Three Vicker's hardness (VH) measurements were randomly taken over the top and bottom surfaces, respectively. Data were analyzed by one-way ANOVA, and independent Student's t-test. Results showed that the QTH LCU (Optilux 401) was statistically superior to the LED LCU (Mr. Light) at all 4 curing distances (p<0.05). Additionally, the greater the curing distance was, the lower the VH value determined. Hence, curing distance cannot be ignored. Further research is required to evaluate the efficiency of different LCUs for clinical use.
Different light sources and curing distances are considered to be the 2 most-important factors influencing the physical properties of light-cured resin composites. The purpose of this study was to evaluate the surface microhardness of resin composites cured with 2 different light curing units (LCUs) at 4 different curing distances. Forty-eight samples of resin composite(shade A3.5) were randomly divided into8groups each with 6 samples. The groups were individually subjected to 8 different curing conditions, and were cured for 40 s. Three Vicker's hardness (VH) measurements were randomly taken over the top and bottom surfaces, respectively. Data were analyzed by one-way ANOVA, and independent Student's t-test. Results showed that the QTH LCU (Optilux 401) was statistically superior to the LED LCU (Mr. Light) at all 4 curing distances (p<0.05). Additionally, the greater the curing distance was, the lower the VH value determined. Hence, curing distance cannot be ignored. Further research is required to evaluate the efficiency of different LCUs for clinical use.