Tooth Bleaching with Nonthermal Atmospheric Pressure Plasma

We demonstrated that room temperature plasma could be used for tooth bleaching. A nonthermal, atmospheric pressure, helium plasma jet device was developed to enhance the tooth bleaching effect of hydrogen peroxide (H₂O₂). All teeth were sectioned sagittally into halves, which were assigned randomly to either the experimental group or the control group. The experimental group was treated with H₂O₂ (28%, 20 μL every 30 seconds) plus plasma (5 W) for 10 minutes; the control group was treated with H₂O₂ alone for the same duration. Removal of the tooth surface protein was demonstrated by scanning electron microscopy images and Ponceau staining. Production of hydroxyl radicals (·OH) was measured by using electron spin resonance spin-trapping. Combining plasma and H₂O₂ improved the bleaching efficacy by a factor of 3 compared with using H₂O₂ alone. Tooth surface proteins were noticeably removed by plasma treatment. When a piece of tooth was added to a solution of H₂O₂ as a catalyst, production of ·OH after plasma treatment was 1.9 times greater than when using H₂O₂ alone. We suggest that the improvement in tooth bleaching induced by plasma is due to the removal of tooth surface proteins and to increased ·OH production.