Evaluation of photopolymerization efficacy and temperature rise of a composite resin using a blue diode laser (445nm).

Abstract

The purpose of this study was to evaluate the photopolymerization efficacy of a diode laser (445nm) for use with a composite containing camphorquinone and to estimate the safety of the method related to the temperature rise. Five cylindrical composite specimens were prepared for each thickness: 1, 2, and 3mm. Three light-curing modes were investigated: a light emitting diode (LED) unit and a diode laser (445nm) with output powers at 0.7W or 3W. Evaluation of the polymerization efficacy was based on Vickers hardness measurements, and the highest temperatures at the bottom of the specimens were recorded using a K-type thermocouple. The highest microhardness was observed after the diode laser curing operating at 3W. A comparison of the microhardness of the 0.7W laser cured specimens with the LED cured specimens showed a statistically significant difference in favor of the laser curing. Laser curing operating at 3W resulted in extremely high temperatures. Laser curing at 0.7W resulted in statistically significantly higher maximum temperatures than did LED curing for both 1mm thick (52.9°C against 45.4°C) and 3mm thick (43.6°C against 40.9°C) specimens. Diode laser (445nm) may be an alternative for photopolymerization of composite materials and may result in a higher degree of conversion and depth of cure of composites than what has been seen with LED curing units when they emit at the same energy density.