It is evidenced that root canal instrumentation produces a smear layer that covers all canal walls. Moreover, this smear layer can harbor bacteria and their products, decrease the dentin permeability to irrigants and medical dressing, and compromise the fluid-tight seal of canals after root filling. Therefore, it is recommended that the smear layer should be removed before processing the root canal obturation. In this regard, a recent study recommended the use of 17% ethylene diamine tetraacetic acid (EDTA) of pH 7.5, for 1 min with passive ultrasonic activation. Moreover, the study suggests that sodium hypochlorite (NaOCl) should not be used as a final irrigant after EDTA.
Source: Al Shehadat S. Smear layer in endodontics: role and management. Journal of Clinical Dentistry and Oral Health. 2017;1(1).
