Over-the-counter whitening strips: Evaluation of color change and hydrogen peroxide penetration into a pulp chamber

To evaluate the color change (CC) and hydrogen peroxide (HP) penetration into the pulp chamber of extracted teeth subjected to different commercial whitening strips, as well as the pH stability and surface morphology induced by these products.

Ninety-six premolars were randomly allocated into six groups: (1) NC, negative control (no bleaching); (2) UP, Up&Up™ Timeless White Whitening Strips; (3) LX, Lumineux® Whitening Strips; (4) CT, Crest® 3DWhitestrips™; (5) WG, Walgreens® Ultra Whitening Strips; and (6) PC, positive control (6% HP, FGM WhiteClass). CC was measured using digital spectrophotometry before treatment and 14 days post-bleaching (ΔL*, Δa*, Δb*, ΔE_ab, ΔE_00,and ΔWI_D). HP penetration into the pulp chamber was analyzed using UV-Vis spectrophotometry, pH stability was measured with a pH meter, and surface morphology by scanning electron microscopy. Statistical analysis was performed using one-way ANOVA, followed by Tukey's post hoc test (α = 0.05).

PC, CT, and UP showed higher ΔE_ab, ΔE₀₀, and ΔWI_D values than LX and NC. Color change was mainly driven by reductions in Δb*. HP was detected in the pulp chamber of PC, CT, and UP, with the highest levels in PC; no HP was detected in LX and NC. Only LX maintained stable pH. SEM analysis showed preserved enamel surface morphology in all groups.

HP-containing whitening strips promoted clinically relevant color changes with lower pulp chamber penetration than the at-home bleaching gel, despite a pH decrease. Peroxide-free strips were ineffective and showed no HP penetration.

Over-the-counter whitening strips vary in effectiveness and biological behavior according to their composition. HP-containing strips may offer effective whitening with a more conservative diffusion profile, while peroxide-free products may not achieve clinically meaningful results.