CONICET | Buscador de Institutos y Recursos Humanos

Objectives It is widely accepted that current tooth whitening treatment effect is based on the oxidizing action of peroxides, even if the mechanism of action remains still unclear. Treatments are claimed to be safe, but several secondary effects have been described, since long application times and high concentrations are needed. A faster whitening ingredient which permits the use of lower concentrations and shorter application times could potentially overcome this problem. In this work, a different approach based on a reducing agent, sodium metabisulfite (MBS), is explored.Materials and methods The reaction between tannic acid (TA) with carbamide peroxide (CP), MBS, and potassium persulfate (PS), as an oxidizing agent, was monitored for 48 hours by measuring its absorbance, comparing their different whitening effects. The reduction process between TA andMBS was confirmed by cyclic voltammetry. An in vitro test was used to observe ifMBSwhitens also stained teeth. Results It is shown thatMBS bleaching effect is faster and higher than CP?s effect over time. PS produced a darkening effect after the 3rd hour because of the strong absorbance of the oxidation metabolite. Cyclic voltammetry showed a progressive increase inthe intensity of the TA anodic peak whenMBS was present, demonstrating that a reduction is taking place. In vitro,MBS showed a faster whitening performance than CP, using lower concentrations.Conclusions Using a TA solution as a staining model, it was possible to show that MBS has a visible bleaching effect through a reduction reaction, faster than CP, both in solution and in vitro. Low concentrations of MBS are effective in whitening. Clinical significance This work shows MBS as a promising candidate to develop novel whitening treatments, which is acting by reducing mechanism instead of oxidation.