Atmospheric Pressure Plasma Jet Composed of Three Electrodes: Application to Tooth Bleaching

Three-electrode plasma jet system consisting of a perforated dielectric tube with two outer and one floating inner electrodes was developed and employed for tooth bleaching. Lowered gas breakdown voltage and increased discharge current were achieved by using the floating inner electrode. Optical emission spectra analysis showed that the rotational temperature of the second positive nitrogen bands was approximate to 290 K and vibrational temperature was approximate to 2 500 K, which means this plasma is in highly non-quilibrium state and nonthermal. The presence of excited He, N-2, H-2(+) and O in the plasma plume was revealed. The plasma jet was used in combination with hydrogen peroxide (H2O2) to remove stains from extracted teeth stained by either coffee or red wine. Combining the plasma jet and H2O2 improved the bleaching efficacy by a factor of 3.1 (coffee) and 3.7 (red wine) compared with using H2O2 alone.