SEM Morphological Evaluation of the Effectiveness of Different Methods Used for Dentinary Cavitary Cleansing

The purpose of this study was to evaluate the ultra-structural morphology of the dentin surface through Scanned Electron Microscopy (SEM) after the application of cavity cleaning products. Forty healthy human molar teeth were used, whose crowns were sectioned on the occlusal third for dentin exposure. The samples were embedded in chemically-activated acrylic resin, in a cast obtained from Polyvinyl Chloride (PVC) pipes. The surface treatment was carried out with a #56 carbide bur coupled in high rotation, producing a residual coating called smear layer. The specimens were randomly divided into six groups according to dentin surface cleaning methods (n=6): G1CO (control)-10s air spray application/30s washing with water jet /10s air spray application; G2AcF-phosphoric acid application at 37%; G3CG-chlorhexidine gel application at 2%; G4CL-chlorhexidine liquid application at 2%; G5AcC-citric acid application at 20%; G6HS-sodium hypochlorite application at 1%. All specimens were fixed in chemical solution until SEM running. For SEM evaluation, the samples were dehydrated with ethanol, then gold-metalized and submitted to morphological analysis, less than 2000x magnification, evaluating the region's cleansing. A qualitative comparison of the smear layer removal was performed for all studies groups through image analysis. The applied substances were responsible for the total or partial smear layer removal, and the ones which removed most of the dentin mud layer were the phosphoric acid at 37%, the liquid chlorhexidine at 2%, the citric acid at 20%, and the sodium hypochlorite at 1%.