Introduction Various factors such as the type of light source, irradiance power, exposure time, curing tip distance, degree of conversion, and type of fillers influence the polymerization of light-cure resins and ultimately, the final properties of the restoration. The present study aimed to compare the efficiency of light-emitting diode (LED) and Quartz tungsten halogen (QTH) curing lights and their effect on the polymerization of microfilled (MF) and nanofilled (NF) composite resins.