Evaluation of curing performance of light-emitting polymerization units

The depth of cure of resin composites is affected by material physical qualities and polymerization source variables. This study evaluated the spectral distribution and intensity of light-emitting diode (LED) and conventional quartz-tungsten halogen curing units, with depth of cure as the testing parameter. The depth of cure was determined using a scraping test, modified from an International Organization for Standards protocol. The light energy spectral distribution (peak wavelength) from each curing unit was determined using a visible-ultraviolet light spectrophotometer. The intensity of each unit (LED and halogen) was measured using LED and conventional radiometers. Data analysis using ANOVA revealed significant differences between the curing units. Based upon depth of cure measurements, the LED units generally were more effective than the conventional halogen unit at polymerizing resin composite. Dentists should be aware that LED curing units offer portability, reduced heat production, and more consistent intensity output per life of the unit.