Do all multi-peak LED light-curing units emit similar light outputs?

OBJECTIVES: To determine if general conclusions can be made about multi-peak light-emitting diode (LED) light-curing units (LCUs). METHODS: Eight contemporary multi-peak LED-based LCUs were tested. The total power and spectral radiant power were measured using a spectroradiometer attached to an integrating sphere. The peak wavelengths, peak heights, and integrated peak areas of the LCUs in the blue and violet regions were analyzed. To determine the potential effect of the resin-based composite (RBC) on the transmission of light from multi-peak LCUs, the light transmitted through 0.5, 2 and 4-mm thick specimens of Filtek Supreme and Tetric plus Fill was also measured. Data were analyzed using one-way ANOVA with Games-Howell tests (α=0.05). RESULTS: There were significant differences in the power and spectral radiant power values among the LCUs. While there were differences in the violet peaks between the standard and high-output, short-exposure modes for five LCUs, there were no differences in the violet peaks between the exposure modes of the Bluephase PowerCure and PinkWave. The CV-215i Plus emitted a pronounced spectral imbalance and emitted very little violet light. The transmitted light decreased with increasing RBC thickness, and violet wavelengths were more affected than blue wavelengths. CONCLUSIONS: The eight multi-peak LCUs exhibited very different blue-to-violet power ratios and distributions; thus, general conclusions about multi-peak LCUs should not be made. RBC thickness and composition significantly affected light transmission, with greater attenuation of violet light. CLINICAL SIGNIFICANCE: General conclusions about the performance of "multi-peak" LCUs are not warranted. Since very little violet light penetrates through the RBC, it is unlikely that a multi-peak LCU will activate violet-dependent photoinitiators at the bottom of bulk-fill RBCs.