Comparison of in-office and at-home tooth-whitening products cytotoxicity

INTRODUCTION: Bleaching teeth to have a whiter and bright smile is a popular trend and currently one can do it at home, without technical support from dentists. However, whitening products are not innocuous and the European legislation is clear limiting the content in hydrogen peroxide (H(2)O(2)), present or released, to 6%, still, products containing up to 40% of H(2)O(2) are commercially available. In fact, the contact time of live tissues with H(2)O(2) agents is usually small, which may restrict side effects, but on the other hand, successively applications as well as at-home careless applications may be harmful. This work aims to verify how whitening products commercialised in Portugal impact on fibroblasts viability. MATERIALS AND METHODS: We used fibroblasts, the main cells of both pulp and gingivae that contact with whitening gels. Mouse embryo fibroblasts (NIH/3T3) were incubated with serial dilutions of Opalescence PF boost 40%, Opalescent PF 16%, Opalescent PF 10% from Ultradent (USA) and Bbryance 0.095% (France) in culture medium for 1-hour. After that period, the culture medium was removed and cell viability was determined using MTT assay. RESULTS: Our results showed a huge decrease in fibroblasts viability after exposure to both product types: containing H(2)O(2) or carbamide peroxide. To achieve conditions considered non-toxic, i.e. showing a reduction in cell viability <30% [1], it was necessary to dilute whitening products at least 100- to 62,500-fold, down to 0.0001–0.0004% H(2)O(2), as shown in Table 1. DISCUSSION AND CONCLUSIONS: Although we cannot extrapolate this effect directly to human teeth, because the concentration of H(2)O(2) arriving at the pulp depends on diffusion through dentinal tubules, our observations are of great concern in particular for gingivae health. Moreover, the whitening products sold for at-home use are as cytotoxic as the in-office product to be applied under the supervision of the dental professional independently of the product type. Since we found that at-home products have similar toxicities, we anticipated that the BBRYANCE gel will induce less severe effects due to his lower H(2)O(2) concentration.