Influence of Manganese Oxide on the Esthetic Efficacy and Toxicity Caused by Conventional In-office Tooth Bleaching Therapy

Abstract

SUMMARY Objective: This study aimed to evaluate the esthetic efficacy, cytotoxicity, and kinetics of decomposition of hydrogen peroxide (H2O2) present in a commercial bleaching gel with 35% H2O2 (BG35%) chemically activated with manganese oxide (MnO2). Methods and Materials: After incorporating 2 mg/mL, 6 mg/mL, and 10 mg/mL of MnO2 into BG35%, the stability of pH and temperature of the products were analyzed. To assess the esthetic efficacy (ΔE and ΔWI), the BG35%s with MnO2 were applied for 45 minutes on enamel/dentin discs (DiE/D). BG35% or no treatment were used as positive (PC) and negative (NC) controls, respectively. To analyze the cell viability (CV) and oxidative stress (OXS), the same bleaching protocols were performed on DiE/D adapted to artificial pulp chambers. The extracts (culture medium + gel components that diffused through the discs) were applied to pulp cells and submitted to H2O2 quantification. BG35% with MnO2 that showed the best results was evaluated relative to kinetic decomposition of H2O2, with consequent generation of free radicals (FR) and hydroxyl radicals (OH•). The data were submitted to the one-way analysis of variance complemented by Tukey post-test (α=0.05). Data on kinetics of H2O2 decomposition were submitted to the Student’s-t test (α=0.05). Results: All the BG35%s with MnO2 showed stability of pH and temperature, and the gel with 10 mg/mL of this activator had an esthetic efficacy 31% higher than that of the PC (p<0.05). Reduction in OXS and trans-amelodentinal diffusion of H2O2 occurred when all the BG35%s with MnO2 were used. The addition of 6 and 10 mg/mL of MnO2 to BG35% increased the CV in comparison with PC, confirmed by the cell morphology analysis. An increase in FR and OH• formation was observed when 10 mg/mL of MnO2 was added to BG35%. Conclusion: Catalysis of BG35% with MnO2 minimized the trans-amelodentinal diffusion of H2O2 and toxicity of the product to pulp cells. BG35% containing 10 mg/mL of MnO2 potentiated the decomposition of H2O2, enhancing the generation of FR and OH•, as well as the efficacy of the in-office tooth therapy.

A new approach for professional dental bleaching using a polymeric catalyst primer

“…In this study, the period of application of the bleaching gels with variable concentrations of H 2 O 2 on enamel covered or not with PCP (45 min) was based on the fact that previous laboratory 9,10,37 and clinical trials 1–4,13,14 used this protocol as control to asses and compare some properties of well‐established and experimental bleaching therapies. In addition, the application of bleaching agents for 45 min, as performed in the present investigation, allows comparing our results with those data obtained from studies in which different strategies of H 2 O 2 degradation were tested using chemical catalytic agents associated or not to photocatalysis approach 11,12,24,25,29 . Even considering the methodological limitations of this in vitro study and that results from laboratory investigations should not be directly extrapolated to clinical situations, 5,35 the use of PCP containing MnO as a chemical catalyst of H 2 O 2 seems to be a promising strategy to reduce the cytotoxicity of professional dental bleaching therapies without harming the excellent esthetic results already reached with this modality of esthetic treatment.…”

“…In addition, the application of bleaching agents for 45 min, as performed in the present investigation, allows comparing our results with those data obtained from studies in which different strategies of H 2 O 2 degradation were tested using chemical catalytic agents associated or not to photocatalysis approach. 11,12,24,25,29 Even considering the methodological limitations of this in vitro study and that results from laboratory investigations should not be directly extrapolated to clinical situations, 5,35 the use of PCP containing MnO as a chemical catalyst of H 2 O 2 seems to be a promising strategy to reduce the cytotoxicity of professional dental bleaching therapies without harming the excellent esthetic results already reached with this modality of esthetic treatment. However, clinical trial are still needed to assess the safety of use and EE of associating PCP with bleaching gels commonly employed in dental offices.…”

“…12,16,19 This metal oxide participates in H 2 O 2 catalysis, promoting its degradation and producing other ROS. 20,21,24,25 The reaction mechanism of MnO with tion. 17 In the present study, it was observed that PCP potentiated the kinetics of H 2 O 2 degradation, resulting in a greater production of OH • radicals.…”

“…Considering that MnO may be effectively used in different tooth bleaching protocols, it is essential at this time, to determine the potential benefits of this metal oxide for bleaching outcomes and pulp cell protection against the toxic effects of H 2 O 2 . Recent investigations showed that the presence of MnO in bleaching gels increases the degradation rate of H 2 O 2 molecules, that result in enhanced EE and reduced cytotoxic of this therapy 24,25 . Thus, the present study added MnO to a cellulose‐derived nontoxic semisynthetic polymer, which has been extensively used in the pharmaceutical industry for controlled drug release 26,27 .…”

“…Recent investigations showed that the presence of MnO in bleaching gels increases the degradation rate of H 2 O 2 molecules, that result in enhanced EE and reduced cytotoxic of this therapy. 24,25 Thus, the present study added MnO to a cellulosederived nontoxic semisynthetic polymer, which has been extensively used in the pharmaceutical industry for controlled drug release. 26,27 The strategy of developing bioproducts containing catalyst molecules, which are applied on enamel before the bleaching gels, has already been reported in the literature.…”