Effect of external tooth bleaching on the surface of resin composites – An in vitro study

Abstract

ObjectivesTo evaluate the effects of external tooth whitening on the surface of two types of resin composites, by scanning electron microscopy (SEM). MethodsEighteen (N=18) specimens were assigned into six groups using two composites: a nanohybrid (Tetric EvoCeram®) and a nanofill (Filtek Supreme XT®); and three protocols: 10% carbamide peroxide (CP) whitening (TW10 and FW10); 22% CP whitening (TW22 and FW22); control group (TC and FC). For each group, the resin composite was introduced into a silicon mold and light-cured according to manufacturer's instructions. Specimens were stored in distilled water (37°C, 24h), polished, and then randomly divided into the mentioned groups. Specimens from the whitening groups were exposed to the CP gels (White Dental Beauty®) for 6h per day. TC and FC specimens were exposed to distilled water. All specimens were stored in an incubator (37°C, 14 days) and observed by SEM. It was measured the hydrogenionic potential (pH) of the CP gels. ResultsSEM analysis of both composites exposed to the CP gels showed surface changes, namely superficial cracks and numerous porous, highlighting a real separation between the resin matrix and the composite fillers, regardless of the gel concentration. These changes were more notorious in the nanohybrid composite. 10% and 22% CP gels have a pH value of 6.71 and 7.42, respectively. ConclusionThe 10% and 22% CP led to changes on both surface composites. These alterations are pronounced in the nanohybrid composite and are independent of the concentrations used.