Effect of Concurrent Coffee Exposure on Whitening Efficacy and Color Stability of At-Home Bleaching Agents

Objectives: This in vitro study evaluated whether coffee exposure during and after at-home bleaching compromises whitening efficacy and long-term color stability across seven bleaching agents differing in active ingredient, concentration, and remineralizing content. Methods: Eighty-four human maxillary incisors were stratified by baseline shade and randomly allocated to seven agents and two immersion media (n = 6 per group): 22% carbamide peroxide (CP), 22% CP with amorphous calcium phosphate (ACP), two 16% CP, 10% CP, 6% hydrogen peroxide (HP), and 6% HP with nanohydroxyapatite. Agents were applied daily for 14 days (8 h CP, 2 h HP). Half of the specimens were immersed in coffee for 48 min/day during bleaching and for consumption-equivalent durations during follow-up; controls were kept in artificial saliva. Color was recorded spectrophotometrically at baseline, days 7 and 14, and 1 week, 1 month, and 6 months post-bleaching, expressed as ΔE00 (CIEDE2000). Data were analyzed with a linear mixed model and Tukey HSD test (α = 0.05). Results: During bleaching, material type (p = 0.014) and time (p < 0.001) exerted significant effects; coffee attenuated cumulative whitening in three CP formulations by day 14, whereas HP agents plateaued after day 7. Post-bleaching, material type was the sole determinant of rebound (p < 0.001), with no effect of immersion medium or time. CP agents rebounded more than HP agents, while the ACP-modified 22% CP behaved like HP agents. Conclusions: Coffee restriction is more critical for preserving whitening during the active bleaching phase than for long-term color stability, which is governed by agent composition.