Effects of sodium hypochlorite on dentin microhardness: a literature review

Abstract

This work presents a literature review on the effects of sodium hypochlorite on dentin microhardness. For the research, materials were searched in the SciELO, BIREME and LILACS databases using descriptors in Portuguese and English. Sodium hypochlorite or NaOCl is the most used irrigant in endodontics due to its germicidal and bactericidal properties, essential for cleaning and disinfecting root canals. During treatment, this solution comes into contact with the dentin, changing its microhardness. NaOCl can cause collagen degradation and disorganization, and the increase in its concentration increases the solution's ability to penetrate dentin and, consequently, the mechanical changes caused are greater, such as the reduction in microhardness. In addition to the increase in concentration, other factors such as time of contact with the solution and temperature can influence the results. NaOCl causes both organic and inorganic changes, causing dentin to dissolve and affecting the adhesion and sealing ability of dental materials. There is no precise value in the literature for the concentration of NaOCl in which an efficient cleaning and disinfection can be obtained without harming dentin microhardness. Consequently, more research is needed in this area in order to determine the appropriate concentrations or even propose an alternative to sodium hypochlorite.