Colour Change, Stability, Sensitivity and Patient Satisfaction after Combined In-Office and At-Home Bleaching with 6% Hydrogen Peroxide: A Longitudinal Study

Introduction Combined in-office and at-home tooth bleaching protocols using hydrogen peroxide (HP) have been proposed to enhance colour stability while maintaining tolerability. However, evidence on the short-term colour stability of at-home bleaching with 6% HP remains limited. Objectives To evaluate: (1) the whitening effect of a 6% HP gel applied for 30 minutes per day over 30 days; (2) colour stability at 30 days after treatment completion; (3) dental sensitivity at the 30-day follow-up according to gender and prior in-office bleaching time (20 vs 40 min); and (4) patient satisfaction. Methods This study included 69 participants previously treated with two in-office sessions using 35% HP (20 or 40 min). All participants subsequently used a 6% HP gel with custom trays for 30 days. Tooth colour was measured instrumentally (CIELAB; Δ E ab and Δ E ₀₀) at baseline after in-office bleaching (T0), immediately after at-home treatment (T1), and 30 days later (T2). Dental sensitivity and patient satisfaction (VAS 0–10) were recorded at T2. Paired t -tests and Mann–Whitney U tests were applied (α=.05). Results During the active bleaching phase (T0–T1), colour changes were pronounced : b* decreased significantly, especially in the incisal third, and both ΔEab and ΔE₀₀ exceeded perceptibility thresholds in most participants. In contrast, during the post-treatment period (T1–T2), changes were markedly smaller : colour coordinates showed only minor variations, indicating short-term stability, although perceptible differences still occurred in a subset of cases. Median dental sensitivity at 30 days was low (3/10), with no significant differences according to gender or prior in-office bleaching time ( P >.05). Patient satisfaction was high (median=9/10), with no differences between groups. Conclusions Across the 30-day at-home bleaching protocol with 6% hydrogen peroxide, colour coordinates showed measurable changes compared with the end of the in-office phase. At 30 days, many participants presented perceptible colour differences relative to T0–T1. During the subsequent month without treatment, variations were smaller and generally limited in magnitude. Dental sensitivity remained low and patient satisfaction high. No significant differences were found between the two in-office exposure times (20 vs 40 minutes) in terms of sensitivity, or satisfaction. Clinical Significance At-home bleaching with 6% HP applied for 30 minutes did not stabilise the whitening achieved with prior in-office treatment and was frequently associated with perceptible colour relapse. The greatest reduction in whitening effect appeared to occur within the first month after in-office bleaching, even when complemented with low-concentration at-home treatment, after which colour tended to remain relatively stable.