Long-Term Whitening Stability in Combined In-Office and At-Home Whitening Protocols: A Randomized Controlled Clinical Trial

Objective: This clinical study assessed the color stability of combined whitening protocols for up to 2 years when using prefilled at-home whitening trays during intervals between in-office whitening sessions. Materials and Methods: In-office whitening containing 35% hydrogen peroxide was used. A prefilled tray with 6% hydrogen peroxide was used for at-home whitening. Sixty-six participants were randomly assigned to three groups: group I, at-home whitening was performed 10 times between three in-office whitening sessions; group II, at-home whitening was performed five times between three in-office whitening sessions; group III, only in-office whitening (three sessions) was performed. Tooth color was assessed before whitening treatment and at 1-day, 3-month, 6-month, 1-year, and 2-year follow-ups using a spectrophotometer. The color differences between the color before whitening and at each follow-up measurement were evaluated based on CIELAB ΔE*_ab, CIE DE2000 ΔE₀₀, and ΔW_ID. Results: Although the ΔE*_ab and ΔE₀₀ in all groups gradually decreased over time, the color stabilities vary in different whitening techniques. Groups II and III showed significantly decreased ΔW_ID (p < 0.05) in the early follow-up periods when compared with that of group I. Conclusions: The use of both in-office whitening and at-home whitening using prefilled trays resulted in longer-lasting whitening efficacy than in-office whitening alone.