Method: The spectral emission (n=5) of experimental LED lamps (peaks) - VIO (410nm), BLUE1 (447nm), and BLUE2 (470nm) were obtained using a spectroradiometer with an integrated sphere. Photon output was calibrated to emit both in low and high irradiance. Emitted power at each wavelength was converted to the number of photons per square centimeter (cm2) and then by dividing by the energy of one photon at that wavelength: Nphl=W/hn. Absorption spectra (n=3) of each photo-initiator were run in between 360-550nm, using a UV-Vis spectrometer and el was calculated. Emission and absorption plots were convoluted and integrated values were recorded. ANOVA and Tukey test (a=0.05) were used for statistical analysis.
Result: CQ showed a blue shift effect in water and lower el than QTX (p<0.001). QTX curing potential were higher than CQ among all lamps (p<0.02), with the highest values provided by VIO lamp (p<0.003); All lamps produced similar values when CQ was present (p=0.08). VIO performed better than BLUEs even when low irradiance was considered (p<0.05).
Conclusion: Considering the curing potential in the violet and blue range, the QTX photo-initiator performed better, but the blue shift effect in water allowed CQ to absorbs more violet photons than in usual 470nm peak. Violet and blue light emission up to 460nm should be considered as the most effective region for free radical generation, but only violet spectrum performed well in lower irradiance.