The aim of study was to investigate the effects of various curing protocols with quartz-tungsten halogen (QTH) or light-emitting diode (LED) light-curing units on the degree of conversion (% DC) of two dual-cured core buildup resin composites. Two dual-cured core buildup resin composites, Clearfil Dc Core Automix (CLF) and Grandio Core Dc (GR), were selected. Specimens were exposed to the polymerization protocols as follows: there was immediate photoactivation or photoactivation delayed by 2 or 5 min by a QTH or LED source, and one group was allowed to chemically polymerize and served as a control (n=6). The % DC of the specimens was determined with attenuated total reflectance-Fourier transform infrared spectroscopy. The GR samples polymerized with QTH for the 5-min-delayed photoactivation had higher % DC values than those self-cured, and the Clearfil Dc Core Automix (CLF) samples with immediate or delayed curing protocols with halogen yielded higher % DC values than the samples that were chemically polymerized. The comparison of the two resin composites polymerized with halogen showed a higher % DC for CLF than for GR in the 2-min-delayed photoactivation. On the other hand, when they were cured with LED, the % DC values of GR significantly increased after the 2-min-delayed photoactivation. In light of the results, it might be stated that CLF polymerized with QTH, could be the better option. GR provided adequate chemical polymerization; therefore, it might be useful in areas in which light curing is not possible. Clinicians should consider the polymerization characteristics of dual-cured resin composites. The use of different composites may require the modification of the application procedures recommended by the manufacturer. (c) 2014 Wiley Periodicals, Inc.