Use of near-IR to monitor the influence of external heating on dental composite photopolymerization.

OBJECTIVES This study was conducted to determine the effect of modest external heating on the photopolymerization kinetics and conversion of commercial dental composite restorative materials. METHODS A transmission-mode, real-time near-infrared spectroscopic technique was used to monitor the photopolymerization process in the composite materials at various temperatures between 23 and 70 degrees C. Several light curing units, differing in spectral output and power densities were compared at the different cure temperatures. Several significantly different commercial composites were compared for their response. RESULTS Regardless of the curing light or composite material used, photopolymerization at a moderate curing temperature of 54.5 degrees C resulted in significantly higher immediate and final conversion values compared with room temperature photocuring. Contrary to the room temperature cured materials, at the elevated cure temperature the extent of post-cure was minor and different curing lights produced very uniform conversion values within a given material. The time required to reach a given level of conversion, established as full conversion with the room temperature cure, was reduced typically by 80-90% using the elevated curing conditions. Complementary kinetic studies confirmed the effect of cure temperature on increasing the polymerization rate in dental composites as significant. SIGNIFICANCE Increasing the temperature of composite resin within potentially biologically compatible limits can significantly influences resin polymerization. These increased rates and conversion could lead to improved properties of composite restorative materials.