Effects of Overnight Whitening Pens on Hydrogen Peroxide Penetration, Color Change, and Enamel Surface Properties

Objective To evaluate hydrogen peroxide (HP) permeability into the pulp chamber, objective color change, and enamel surface morphology after overnight use of over‐the‐counter (OTC) whitening pens. Materials and Methods Fifty sound premolars were assigned to five groups ( n = 10): control, Optic White Pen LED (OW), Colgate Luminous White Whitening Pen (LW), Equate Teeth Whitening Kit (EQ), and Whiteness Perfect 10% (WP). Fifteen molars were used for enamel surface analyses (microhardness and roughness). Products were applied for 8 h/day for 10 days. HP penetration (μg/mL) and color change (Δ E ab , Δ E 00 , and WI D ) were measured by spectrophotometer. Initial HP concentration and pH were determined by titration and pH meter. Data were analyzed using ANOVA ( α = 0.05). Results EQ showed the highest HP concentration and the lowest pH. HP penetration was significantly higher for EQ and lowest for WP ( p < 0.05). No significant differences in Δ E ab and Δ E 00 were observed among products, while WI D increased over time in all groups. Enamel surface changes were similar, except for EQ, which showed reduced microhardness ( p < 0.05). Conclusions Overnight OTC whitening pens showed comparable cumulative bleaching efficacy. However, EQ resulted in greater pulpal HP penetration and enamel softening. Clinical Significance Prolonged overnight OTC whitening pen use may increase pulpal exposure and enamel softening risk, reinforcing cautious use and professional supervision.