Effective and long-lasting tooth bleaching by non-thermal atmospheric pressure plasma: A 6-month evaluation

The problem associated with bleached teeth is to return to the original tooth color over time. Because the long-term color stability after tooth bleaching is very important, novel technique is requested. This study is to evaluate the long-term color stability of tooth bleached by nonthermal atmospheric pressure plasma with 15% hydrogen peroxide (HP) or 15% carbamide peroxide (CP). Extracted human teeth were assigned to 4 groups (n = 10): Group 1 was treated with plasma activated 15% HP; Group 2 with 15% HP alone; Group 3 with plasma-activated 15% CP gel; and Group 4 with 15% CP alone. A low-frequency driven helium plasma jet was used. After a 30-min application, teeth were immersed in artificial saliva, and color was assessed using the CIELAB system over 6 months, with the overall color changes (ΔE) calculated relative to baseline. Hydroxyl radical concentration (·OH) was detected using methylene blue (MD) dye. Statistical analyzes were performed with Student's t-test, one-way analysis of variance, and post-hoc Duncan tests. Results: Combination treatment of plasma and 15% HP/CP resulted in higher color stability than 15% HP/CP alone throughout the whole observation period (p <; 0.05). The activity of ·OH in combined plasma and low concentration 15% HP/CP was enhanced, relative to bleaching agents alone (p <; 0.05). Long-term color stability of tooth bleaching using plasma with 15% HP/CP was retained for 6 months. Tooth bleaching with plasma is an important factor for ·OH production, which is key to the bleaching effect.