Comparison of Different Bleaching Protocols Efficacy on Artificially Tea-Stained Teeth up to 24 Months Post-Treatment

Abstract

Objective: In vitro investigation of four bleaching protocols efficiency, on artificially tea-stained human teeth, up to 24-month post-treatment. Methods: 100 intact, extracted, human incisors were randomly divided (n=4x25/group) and underwent black tea staining. The bleaching protocols applied per group were: 1. (BH, at-home) 10%CaP for 5 days (120min/day), repeated twice, 2. (BO1, in-office) 40%HP for 3 successive applications (15 min/application), repeated twice, 3. (BO1, in-office) 40%HP for 3 successive applications (15 min/application), repeated 3 times and 4. (BH+BO1, at-home/in-office) starting with BH, interval of 2 days, followed by BO1. The color was measured before bleaching(t0), right after staining(t1), after each bleaching procedure(t2), 3(t3), 6(t4) and 24 months(t5) after treatment, with a colorimeter (Braive Instruments) in CIEL*a*b*system. ΔΕ*values were calculated relative to t0. Statistical analysis was performed by Mann-Whitney U and Friedman and Wilcoxon Signed Ranks tests (a=0.01). Results: All bleaching protocols, at t2 induced increase in L*, return of a* to before-staining values, shifting of b* to blue (BO1, BO2) and improvement of tooth color ( ΔΕ*) with no statistically significant difference among protocols. All color coordinates presented gradual rebound at t3. Regarding ΔΕ*, tooth color reached after-staining values for BH, BO1, BO2 up to 24 months, while bleaching effect was partially preserved for BH+BO1 group. Conclusion: At-home and in-office bleaching protocols provided similar whitening effect on tea-stained teeth, immediate after application. However, rebound effect started at 3 and progressed up to 24 months post-treatment. The combination of at-home and in-office treatment showed relative better potential in bleaching color preservation.