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 ≈290 K and vibrational temperature was ≈2 500 K, which means this plasma is in highly non‐quilibrium state and nonthermal. The presence of excited He, N2, N 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. An atmospheric pressure plasma jet has attracted great interest in biomedical applications thanks to its simplicity of the design and its diverse capabilities. This study proposed a design of a safe and reactive, nonthermal atmospheric pressure plasma jet, and demonstrated that the plasma jet enhanced the tooth bleaching effect. We expect that this study can contribute to widening the application field of atmospheric pressure plasma.