Effects of neutralizing or antioxidant agents on the consequences induced by enamel bleaching agents in immediate resin composite restorations

Abstract

Purpose: Bleaching agents are claimed to impair the bonding to the tooth structure when resin composite restorations are immediately performed. This study aimed to evaluate the effect of a neutralizing solution (10% sodium bicarbonate) or an antioxidant agent (10% sodium ascorbate) on the immediate or delayed (15 days) shear bond strength (SBS) of composite restorations performed on enamel. Seventy flat buccal enamel surfaces obtained from bovine incisors were divided into seven groups (n = 10): control group, unbleached enamel, restored (3M ESPE/Adper Single Bond 2/Filtek Z350XT) (G1); bleached, immediately restored (G2); bleached, delayed restoration (G3); bleached, antioxidant (sodium ascorbate), immediately restored (G4); bleached, antioxidant, delayed restoration (G5); bleached, neutralizing (sodium bicarbonate), immediate restoration (G6); bleached, neutralizing, delayed restoration (G7). Specimens were submitted to SBS test and examined after failure using scanning electron microscopy (SEM). Results were statistically analyzed with ANOVA/Tukey’s tests (5%). Bonding to enamel immediately restored after bleaching (G2) was significantly lower than G1 (unbleached enamel; p < 0.05). Applying the antioxidant or neutralizing agent significantly improved the bonding to enamel compared with G2 (bleached, immediate restored), irrespective of the restoration time (immediate or delayed) (p < 0.05). No significance was found between the two agents when applied after bleaching, and compared with the control group, regardless of evaluation time (p > 0.05). SEM images demonstrated adhesive failures in the bleached, immediately restored group (G2). G3–G7 exhibited majority of cohesive and mixed failure patterns. 10% sodium bicarbonate or 10% sodium ascorbate neutralizes the negative immediate and delayed effects of bleaching on bond strength of enamel bleached enamel.

Keywords:

• Dental enamel
• tooth bleaching
• shear strength
• sodium bicarbonate

Acknowledgments

This study was developed as partial fulfillment of the requirements of Dr. Romani’s graduate-level specialization degree at HRAC – USP Bauru, Brazil. The authors are grateful to Prof. Dr. Alejandra Hortencia Miranda González (UNIAN-SP, Brazil) for the technical support for the chemical analysis. The authors are also grateful to Prof. Dr. Francisco André Ossamu Tanaka from NAP/MEPA (Support Research Nucleus / Electron Microscopy Applied to Agriculture - ESALQ/USP) – Piracicaba, for the support in the SEM analysis. The authors are also grateful to FOB-USP for the technical support in the bond strength test. This work was also in part supported by PEST-1408 and INDI1527 ‘Programa de Consolidación de Indicadores: Fomento Plan Estatal CEU-UCH 2014-2016’ to Prof. Dr. Salvatore Sauro. The authors would like to thank Dr. Jonathan Dixon from (University CEU Cardenal Herrera, Valencia, Spain) for the editing support.