Effects of several cleaning substances, time of acid etching and its impact in the bond strength of the adhesive system on bovine dentin

Abstract

The objective this study is to evaluate the cleaning ability of the dentin surface, contaminated by an epoxy-based sealer (AH Plus), provided by ethanol or xylol and its effect on the interface dentin/dentin adhesive system, by assessing formation of the hybrid layer and interference on bond strength of dentin adhesive system, immediately or after 7 days of dentin cleaning. In study 1, fifty fragments of dentin (5mm x 5 mm x 3 mm) will be cut from the middle third of the tooth crown. The fragments will be immersed in a solution of sodium hypochlorite solution (NaOCl) for 15 minutes, 17% EDTA for 3 min and in NaOCl for 1 min. After dried, the dentin surface of forty fragments will be contaminated with an epoxy-based sealer (AH Plus) for 15 minutes. The surface will be cleaned with ethanol (n=20) or xylol(n=20). The fragments will be distributed into four experimental groups: G1 (alcohol, acid etching immediate), dentin will be cleaned with ethanol and immediately after acid etching with phosphoric acid 37%, G2 (Xylol, conditioning immediate acid), similar to G1, using xylol ; G3 (alcohol, acid etching after 7 days), but similar to G1 etching, performed 7 days after; G4 (xylol, acid etching acid after 7 days), similar to G3 using xylene. Ten fragments uncontaminated and only submitted to acid etching will serve as control (G5). After etching, the dentin surface will be washed with water, for 10 seconds, dried and prepared for scanning electron microscopy. After processing, the specimens will be evaluated by MEV (500X) and the persistence of residues on the dentin surface is quantified. The data will be submitted to the Kruskal Wallis test (p = 0.05). In study 2, the labial surface of fifty bovine incisors will be worn with sandpaper until the exposure of the dentin surface. The specimens will be subjected to the same protocols described in experiment 1 composing 4 experimental groups and one control. Immediately after performing the etching on this surface adhesive system is applied and reconstructed with composite resin. The specimens will be longitudinally sectioned and prepared for microscopic analysis. The intradentinal extension of the hybrid layer will be obtained in confocal laser microscopy (1024X) and quantified using Image J. The data will be submitted to Kruskal Wallis test (p = 0.05). In study 3, the labial surface of fifty bovine incisors will be worn and embedded in acrylic resin. The specimens will be divided into five groups (n=10), similar to protocols described in experiment 2. Following, after application of the adhesive system, composite resin cylinders are attached to the underlying dentin. After 24 hours, the microshear bond test, in electromechanical testing machine, will be performed. The data obtained (in MPa) are analyzed using the Kruskal-Wallis test (p = 0,05). (AU)