Effectiveness of different carbamide peroxide concentrations used for tooth bleaching: an in vitro study

Abstract

Objectives This in vitro study evaluated the effectiveness of three carbamide peroxide concentrations used for tooth bleaching treatments. Material and Methods Sixty bovine dental slabs (6x6x3 mm) were obtained, sequentially polished, submitted to artificial staining (baseline) and randomized into four groups (n=15), according to the bleaching agent concentration: distilled water (control), 10% (CP10), 16% (CP16) or 37% (CP37) carbamide peroxide. CP10 and CP16 were covered with 0.2 mL of the respective bleaching gels, which were applied on enamel surface for 4 h/day during two weeks. Samples of CP37 were covered with 0.2 mL of the bleaching gel for 20 min. The gel was light activated by two 40-s applications spaced by 10-min intervals. The gel was renewed and applied 3 times per clinical session. This cycle was repeated at 3 sessions with 5 days of interval between them. Tooth shade evaluations were done with a digital spectrophotometer at T0 (baseline), T1 (after 1-week of treatment) and T2 (1-week post-bleaching). Tooth shade means were statistically analyzed by Kruskal-Wallis and Friedman's tests and color parameters were analyzed by two-way ANOVA and Tukey's test (p<0.05). Results At T1 and T2 evaluations, tooth shade was significantly lighter than at baseline for all treatment groups, considering the color parameters ΔL*, Δa*, Δb*, ΔE* (p<0.001) or tooth shade means (p<0.001). CP37 group showed lower shade mean change than CP10 and CP16 at T1 (p<0.01), but this difference was not statistically significant at T2 (p>0.05). Conclusions One week after the end of the treatment, all carbamide peroxide concentrations tested produced similar tooth color improvement.

Preferences on Vital and Nonvital Tooth Bleaching: A Survey Among Dentists from a City of Southern Brazil

“…In fact, dentist-supervised tooth bleaching using 10% CP gel with custom-made trays is still considered the gold-standard treatment for tooth discoloration (5,15,16) and it is the only agent concentration accepted by the American Dental Association (ADA) for at-home bleaching (17). The main advantages of this technique are the ease of use, shorter chairtime and low incidence of tooth sensitivity and gingival irritation (3,5,18). Over 30% of the surveyed dentists answered to use CP at concentrations above 10%, which could be related to the assumption that increasing the bleaching agent concentration would enhance the whitening effect as there would be more oxygen release allowing a stronger and faster outcome (3,5).…”

“…The main advantages of this technique are the ease of use, shorter chairtime and low incidence of tooth sensitivity and gingival irritation (3,5,18). Over 30% of the surveyed dentists answered to use CP at concentrations above 10%, which could be related to the assumption that increasing the bleaching agent concentration would enhance the whitening effect as there would be more oxygen release allowing a stronger and faster outcome (3,5). However, clinical trials have demonstrated that increasing the bleaching agent concentration did not improve significantly the whitening effect (18,19).…”

“…Basically, the mechanism of action of bleaching agents is similar. Peroxide-containing agents break down into water and oxygen, which diffuses through the dental structure, causing oxidation and reduction of organic pigments that are located mainly within the dentin structure, ultimately producing the whitening effect (3).…”

“…While nonvital tooth bleaching is performed at the dental office using strong peroxide agents, such as high concentration hydrogen peroxide (HP) or hydrogen peroxide-releasing agents (carbamide peroxide -CP and sodium perborate -SP) (2), vital tooth bleaching can be performed with high concentration (in-office) or low concentration agents (at-home bleaching or over-thecounter -OTC -products) (1,3,4). Agent concentration and technique have been claimed to influence the bleaching outcome (2,5).…”

“…Some adverse effects are reported on vital tooth bleaching, including tooth sensitivity, gingival irritation, reduced adhesion to dental tissues and alterations in the dental structure (3)(4)(5). In nonvital bleaching, the occurrence of external root resorption, morphological alterations in dental tissues, alteration of dental materials' properties and decrease of tooth resistance and adhesion have also been reported (2,6,7).…”