At-home bleaching with carbamide peroxide with concentrations below 10%: bleaching efficacy and permeability in the pulp chamber

Abstract

Objectives: To evaluate the bleaching efficacy and permeability of hydrogen peroxide (HP) in the pulp chamber of human teeth bleached with lower concentrations of carbamide peroxide gel (4%, 5% and 7% CP).

Materials and methods: Bleaching gels with lower concentrations were formulated and a commercial standard gel, 10% CP, was used as a reference. Fifty-six human premolars were randomly divided into four groups. Applications of the bleaching gel were made for 3 h for 21 days. The bleaching efficacy was evaluated by digital spectrophotometry on 1, 7, 14 and 21 days, with analysis in the ∆E_ab, ∆E₀₀ and WI_D color spaces. The concentration of HP in the pulp chamber was measured in the same periods by UV-Vis spectrophotometry (µg/mL). Two-way repeated analysis of variance (ANOVA) examined bleaching efficacy and HP permeability, followed by Tukey's post-hoc test (α = 0.05).

Results: All groups showed significant color changes, with no statistical differences after the second and third week of bleaching (p > 0.05). The 'time' factor was statistically different (p < 0.05), increasing the bleaching efficacy throughout the treatment. The 4% CP group had lower HP levels in the pulp chamber (p < 0.05).

Conclusions: The results seem promising, revealing that low concentration gels are as effective as 10% CP with the benefit of reducing the amount of HP in the pulp chamber.

Clinical relevance: Low concentration 4% PC and 5% PC maintains bleaching efficacy, reduces the penetration of HP peroxide into the pulp chamber, and may reduce tooth sensitivity.

Keywords: Carbamide peroxide; Dental enamel permeability; Dentin permeability; Tooth bleaching.