Evaluation of hydrogen peroxide permeability, color change, and physical-chemical properties on the in-office dental bleaching with different mixing tip

OBJECTIVE

This study aims to assess hydrogen peroxide (HP) penetration into the pulp chamber, color change (CC), physical-chemical properties, and material wastage (MW) and material used (MU) in mixing tips when using in-office bleaching gels with two different mixing tips.

MATERIALS AND METHODS

Forty teeth were divided into five groups (n = 8) based on the bleaching gels used (Pola Office +37.5% [PO+] and Whiteness HP Automixx Plus 35% [AM+]) and the mixing tip types (T-Mixer and Helical). A negative control group was treated with ultra-purified water. HP concentration was measured using UV-Vis, and CC was evaluated with a digital spectrophotometer. Initial concentration, pH, and viscosity were measured through Titration, a Digital pH meter, and Rheometer, respectively. MW and MU were measured using a precise analytical balance. Statistical analysis included two-way ANOVA, Tukey's, and Dunnett's test (α = 0.05).

RESULTS

A higher HP concentration was observed with PO+ with the Helical mixing tip in comparison with AM+ (p = 0.01). No significant differences in CC or MU were found for different mixing tips (p = 0.001). The T-mixer mixing tip resulted in significantly less MW (p < 0.00001) and improved mixture homogeneity and viscosity.

CONCLUSIONS

Utilizing a T-mixer with self-mixing bleaching gels achieves comparable CC while reducing MW. Moreover, it decreases HP penetration when using PO+.

CLINICAL SIGNIFICANCE

For the application of a self-mixing in-office bleaching gel, a T-mixer mixing tip should be recommended, as it reduces the penetration of hydrogen peroxide into the pulp chamber when using PO+, while also minimizing gel wastage.

Difusão do Peróxido de Hidrogênio em Dentes Submetidos a Diferentes Protocolos de Clareamento

Objetivos: avaliar a concentração de Peróxido de Hidrogênio (PH) que alcança a câmara pulpar, utilizando géis clareadores de mesma marca comercial. Métodos: 90 pré-molares foram divididos em 9 grupos de acordo com o tratamento: Controle (sem tratamento clareador) [C], Peróxido de Carbamida (PC) 10% [PC10%], PC 16% [PC16%], PC 22% [PC22%], Peróxido de Hidrogênio (PH) 4% [PH4%], PH 6% [PH6%], PH 7 ½% [PH7 ½%], PH 10% [PH10%] e PH 35% [PH35%]. Os dentes foram seccionados e inserido tampão de acetato na câmara pulpar. Os géis clareadores foram aplicados de acordo com as recomendações dos fabricantes. A solução de tampão foi removida e adicionada a esta, soluções de leucocristal violeta e enzima peroxidase. Os dados foram submetidos a ANOVA e teste de Tukey para contraste das médias (a 0,05). Resultados: Maior quantidade de PH foi observado em protocolo de consultório [PH 35%] quando comparado com clareamento caseiro (p 0,000). Não houve diferença estatisticamente significante   (p 0,649) entre os protocolos caseiros. O [PC 10%] libera aproximadamente 3,5% de PH, o qual se difunde na câmara pulpar em quantidades semelhantes ao grupo [PH 4%]. Os grupos [PC 22%] e [PH 10%] também foram similares. Conclusões: A quantidade de PH que alcança a câmara pulpar não é proporcional a concentração inicial de PH dos géis clareadores.Palavras-chave: Peróxido de Hidrogênio. Clareamento Dental. Permeabilidade do Esmalte Dentário.

Effects of the concentration and composition of in-office bleaching gels on hydrogen peroxide penetration into the pulp chamber

In tooth whitening, the hydrogen peroxide (HP) diffuses in the enamel and dentin, reaching the pulp. This in vitro study aimed to quantify the penetration of HP in the pulp chamber in teeth submitted to bleaching agents of different concentrations of HP without calcium (HP 20% [20CF], HP 35% [35CF]) and with calcium (HP 20% [20CC], HP 35% [35CC]).

METHOD

Fifty human premolars were sectioned 3 mm from the cemento-enamel junction and the pulp tissue was removed. The teeth were divided into five groups according to treatment and with a control group (n=10). An acetate buffer solution was placed in the pulp chamber of all teeth. The control group was exposed only to distilled water, while the other groups were treated with a bleaching procedure, according to the manufacturer's recommendations. After treatment, the acetate buffer solution was transferred to a glass tube in which leuco-crystal violet and peroxidase solutions were added, resulting in a blue solution. The optical density of this blue solution was determined spectrophotometrically and converted into micrograms equivalent to the HP. Data were analyzed using analysis of variance and Tukey tests (α=0.05).

RESULTS

The HP concentration did not affect the HP inside the pulp chamber, but the presence of calcium significantly reduced it (p<0.0001).

CONCLUSION

The amount of HP that reaches the pulp chamber depends on the bleaching protocol and the product employed, and it seems to be less affected by HP concentration.