Biological and Esthetic Effects of Experimental Tooth-bleaching Agents Formulations

Objectives: The aim of this study was to evaluate the aesthetic effectiveness and cytotoxicity of 20% and 10% H₂O₂ experimental tooth-bleaching agents in association with the chemical activators.
Methods: The bleaching gels were formulated with carbopol as thickening agent associated or not to 1 mg/mL of manganese oxide (MnO), ferromanganese oxide (MnFe₂O₄) or peroxidase (PR), which were then mixed with H₂O₂ phase at 10 or 20% in a 1:3 proportion. These formulations were applied for 45 minutes onto enamel/dentin discs adapted to artificial pulp chambers and the trans-enamel and trans-dentinal diffusion products were applied to cultured human dental pulp cells (HDPCs) for 1 h. Non-bleached samples or bleached samples without chemical activators (10% or 20% H₂O₂) were used as negative (NC) and positive (PC) controls, respectively. The amount of residual H₂O₂, reactive oxygen species (ROS) and hydroxyl radicals (HO) was monitored (Dunnet's; α=5%). HDPCs viability and oxidative stress were determined. Residual H₂O₂ capable of diffusing through the discs was quantified and the bleaching effectiveness (DE) was assessed (ANOVA/Tukey; α=5%).
Results: All chemically-activated bleaching agents minimized the HDPCs oxidative stress generation and promoted higher cell viability values than PC groups (p<0.05). This effect was associated with reduction of residual H₂O₂ diffusion through dental structures for the groups containing chemical activators in comparison to PC groups (p<0.05). When compared with PC, increased ΔE values was observed in that group in which PR was incorporated to carbopol, regardless the H₂O₂ concentration (p<0.05). This effect was associated with an intense increase in ROS and HO production in the gels containing this activator (p<0.05).
Conclusions: Therefore, the addition of PR in H₂O₂-based bleaching gels enhances the production of free radicals at tooth surface, minimizing cell toxicity and improving the aesthetic outcome.