Trans-enamel and trans-dentinal cytotoxic effects of a 35% hydrogen peroxide bleaching gel applied on non-restored and restored teeth with composite resin

Abstract

Aim: To evaluate the trans-enamel and trans-dentinal cytotoxic effects of a 35% hydrogen peroxide (H2O2) bleaching gel applied on non-restored and restored teeth with composite resin submitted to aging by water storage and thermocycling. Material and Methods: Enamel/dentin discs will be obtained from bovine central incisors and restored or not with self-etching adhesive system (Adper SE Plus, 3M ESPE) and composite resin (Filtek™ Z350, 3M ESPE). These discs will be storage in water for 24 hours or 6 months and then, placed individually in artificial pulp chambers and distributed according to the following treatments: non-restored teeth stored for 24 hours submitted or not to bleaching procedures; non-restored teeth stored for 6 months submitted or not to bleaching procedures; restored teeth stored for 24 hours submitted or not to bleaching procedures; and restored teeth stored for 6 months submitted or not to bleaching procedures. The bleaching gel will be left in contact with the enamel surface for 15 minutes. The extracts will be collected and applied on previously cultured MDPC-23 cells for 1 hour. Cell metabolism and cell morphology will be evaluated by MTT assay and SEM, respectively. In addition, alkaline fosfatase expression will be analyzed as well the expression of genes that encode for TNF-α, IL-6, IL-1ß, and COX-2 by means of real time RT-PCR. The data obtained from tests will be analyzed statistically. (AU)