Purpose: The purpose of this study was to evaluate the curing efficiency of 8 light- and dual-cured denture reliners. Materials and Methods: The curing efficiency was measured with Fourier infrared micromultiple internal reflectance spectroscopy, calculating the percentage of remaining carbon double bonds on the top and bottom surfaces of each specimen immediately after exposure to the extraoral light-curing unit according to the manufacturer's instructions and after 1 week of storage in dark and dry conditions. Another group of specimens was photopolymerized initially through a denture base resin prior to the extraoral light-curing polymerization. Five specimens of each reliner were tested. Results: The dual-cured reliners showed no statistically significant differences (P > 0.05) between top and bottom surfaces after immediate exposure to the light-curing unit. On the contrary, light-cured reliners revealed significant differences. The majority of the reliners showed reduction of the percentage of remaining carbon double bonds at both surfaces after 1 week of storage in dark and dry conditions. Photopolymerization of lightcured reliners through a denture base resin induced an increased amount of remaining carbon double bonds, whereas no effect was observed in dual-cured materials. Conclusion: Dual-cured denture liners exhibited distinct advantages over light-cured ones concerning the curing efficiency.