Emission characteristics and effect of battery drain in "budget" curing lights

Recently, "budget" dental light-emitting diode (LED)-based light-curing units (LCUs) have become available over the Internet. These LCUs claim equal features and performance compared to LCUs from major manufacturers, but at a lower cost. This study examined radiant power, spectral emission, beam irradiance profiles, effective emission ratios, and the ability of LCUs to provide sustained output values during the lifetime of a single, fully charged battery. Three examples of each budget LCU were purchased over the Internet (KY-L029A and KY-L036A, Foshan Keyuan Medical Equipment Co, and the Woodpecker LED.B, Guilin Woodpecker Medical Instrument Co). Major dental manufacturers provided three models: Elipar S10 and Paradigm (3M ESPE) and the Bluephase G2 (Ivoclar Vivadent). Radiant power emissions were measured using a laboratory-grade thermopile system, and the spectral emission was captured using a spectroradiometer system. Irradiance profiles at the tip end were measured using a modified laser beam profiler, and the proportion of optical tip area that delivered in excess of 400 mW/cm² (termed the effective emission ratio) was displayed using calibrated beam profile images. Emitted power was monitored over sequential exposures from each LCU starting at a fully charged battery state. The results indicated that there was less than a 100-mW/cm² difference between manufacturer-stated average tip end irradiance and the measured output. All the budget lights had smaller optical tip areas, and two demonstrated lower effective emission ratios than did the units from the major manufacturers. The budget lights showed discontinuous values of irradiance over their tip ends. One unit delivered extremely high output levels near the center of the light tip. Two of the budget lights were unable to maintain sustained and stable light output as the battery charge decreased with use, whereas those lights from the major manufacturers all provided a sustained light output for at least 100 exposures as well as visual and audible indications that the units required recharging.