Objective: The objective of this study was to evaluate the influence of 3 different light curing protocols on the degree of conversion(DC) of 4mm thickness of a bulk- fill composite SDR ( Smart Dentin Replacement) when irradiated for constant time increments of 20 seconds and analyzed with Fourier Transform Infrared Spectrometer using the Attenuated Total Reflectance method( FTIR-ATR). Methodology: SDR was placed in 8mm diameter and 4mm thick metal molds and light cured from top at 300,550 and 800 mW/cm2 for 20 seconds each and stored in light proof boxes. The specimens were then subjected to FTIR-ATR analysis for assessing the DC. Results: DC showed a linear increase with the light intensity when exposure time was kept constant. Highest DC of 67% was obtained for SDR when irradiated  at  800mW/cm2  for 20 seconds. Conclusion: Bulk fill composites like SDR can attain high enough DC following polymerization when cured to a depth of 4mm. The DC obtained was directly related to the intensity of light irradiated.
Keywords: Bulk-fill composite, degree of conversion, FTIR-ATR, light intensity.