Evaluation of light output from light-curing units used in a public oral health service in Brazil.

This observational field study aimed to evaluate the radiant power (mW), emission spectra (mW/cm²/nm), irradiance (mW/cm²), and the light tip integrity of 40 light-curing units (LCUs) used in 16 public oral health service units in the city of Uberlândia, Minas Gerais, Brazil. The radiant power and emission spectrum were measured using a spectrometer attached to an integrating sphere. Irradiance profiles were obtained using a Beam Profiler. The tips were photographed and classified in 4 categories: A. undamaged, B. contaminated by resin residue, C. damaged, and D. contaminated and damaged. Data were analyzed by one-way ANOVA (α = 0.05), and the emission spectra and beam profiles were analyzed descriptively. The LCUs tested were single-peak light-emitting diode units, and 85% of the LCUs had damaged light tips. The radiant power values were significantly different between the LCUs (P < 0.001) and ranged between 94.2 and 588.2 mW. The irradiance ranged from 255.8 to 1597.8 mW/cm². The LCU tip diameter ranged from 6.1 to 8.3 mm. Two-dimensional beam profiles show that the light distribution was not homogeneous across the tips, and an irradiance peak was often observed at the center of the LCUs with smaller tips. Only 15% of the LCU were undamaged, reflecting substantial variability in radiant power and irradiance delivered. Although no statistically significant differences were observed among tip condition categories, these conditions showed a trend toward reduced and inhomogeneous light output.