Corrections of the root canal irrigation protocol: Primum non nocere

Abstract

Endodontic irrigant play an important role in the elimination of microorganisms from the root canal system, dissolving organic tissue, removing of debris and the smear layer. Sodium hypochlorite (NaOCl) is a powerful antiseptic agent which dissolves the organic part of dentin, vital and necrotic tissue and neutralizes toxic products. Its antibacterial effect increases with increasing concentration. Due to inadequate surface tension, NaOCl has restricted access to narrow and accessory canals. Chlorhexidine (CHX) has an antibacterial efficacy comparable to NaOCl, while being effective against certain NaOCl resistant bacterial strains. Effective root canal disinfection is achieved due to substantivity, i.e. continued and prolonged antimicrobial effect. Unlike NaOCl, it's not able to dissolve organic material within the root canal. Ethylene-diamine-tetra-acetate (EDTA) removes the inorganic part of the dentinal wall facilitating the passage of endodontic instruments. It doesn't act on the organic smear layer and hasn't antimicrobial properties. It seems that not all irrigants not able to fulfill all the necessary requirements, so their combined use is necessary. Studies have shown that there are interactions between some irrigants, which are undesirable and may compromise endodontic therapy. A mixture of NaOCl and CHX leads to staining of the teeth and the creation of an orange-brown precipitate, which either remains in the dentinal wall or exceeds to the periapical tissues. CHX and EDTA combination also produces a precipitate. This precipitate reduces permeability, disruptives hermetic obturation and can act as a chemical smear layer. It was found that the precipitate consist of the para-chloroaniline, which has been experimentally shown to have toxic effects on the tissue around the root apex. Simple adjustments in the irrigation protocol can prevent the occurrence of adverse reactions between endodontic irrigants. © 2014 Faculty of Medicine in Niš.