Intensity of quartz-tungsten-halogen light-curing units used in private practice in Toronto

ABSTRACT Background The authors conducted a study to determine light intensity and heat/glare measurements of quartz-tungsten-halogen (QTH) light polymerization units used in dental offices. Methods Research assistants visited 100 dental offices and assessed 214 QTH light units. They recorded each unit's model, age, service history, light intensity and heat/glare emissions. Results Mean light intensity was 526 milliwatts per square centimeter (120–1,000 mW/cm 2 ), with 26 units having intensity less than 300 mW/cm 2 . The mean light unit age was 5.6 years. Light units older than three years had significantly lower output intensities than those that were one, two or three years old. The authors found a wide range of heat/glare measurements (3–300 mW/cm 2 ), with 4.6 percent of the units having values greater than 50 mW/cm 2 , including three with values of more than 200 mW/cm 2 . The mean light intensity of units serviced in the preceding year was 539 mW/cm 2 ; it was 418 mW/cm 2 for units serviced from one to six years previously. Conclusions Light intensity and heat/glare values varied among the 214 units; some units had values well outside the recommended levels. Each unit's age and service history significantly affected its intensity. An awareness campaign is needed to promote testing, repair or replacement of light polymerization units. Periodic testing of light polymerization units should be considered by regulatory bodies to ensure optimum quality of composite restorations. Clinical Implications Light polymerization units in some private dental offices in Toronto had intensities that may result in composites restorations with inferior properties. Dentists need to regularly monitor the intensity of the light polymerization units and maintain the units to ensure quality composite restorations.