Aim: To evaluate the efficacy of polymerization of two composite resins with QTH and LED light curing units. Materials and methods: Total 40 specimens were prepared with Microhybridcomposite (Filtek Z250) and Nanofilled composite (Filtek Z350 XT) and cured with LED light curing unit Stealth SOFT (Equinox) and Quartz tungsten halogen (QTH) light curing unit QHL75 curing light (Dentsply).Thus, 4 experimental groups (n= 10) were prepared according to the composite resin and light curing unit that was used. The specimens were stored in distilled water in a container for 24 hours and microhardness was determined by a Vickers Microhardness Tester (Reichert, Austria). Microhardness measurements were performed by applying a 10 gm load for 10 seconds at three points, 1 mm apart on the specimens bottom surface. The comparison of means of different groups was done using statistical analysis by Tukey’s test and Kruskal Wallis test. Results: The results showed no statistically significant differences between the light curing units and composite resins (p=0.9333). Vickers Hardness number (VHN) or microhardness value for LED cured Microhybrid composite was found to be 60.23 whereas LED cured Nanofilled was 58.Vickers Hardness number (VHN) for Halogen cured Nanofilled was 59.6 as compared to Halogen cured Microhybrid which was found to be 58.7. Conclusion: The LED curing light provided the maximum hardness values for the microhybrid composite resin as compared to the conventional QTH curing light.The QTH curing light provided the maximum hardness values for the nanofilled composite resin as compared to the LED curing light
