Apical periodontitis has been shown to be a biofilm-related disease, because the root canal infection consists of biofilm. Because root canal systems are anatomically complex, instruments cannot reach all canal surfaces. Thus, infected root canals are routinely treated chemomechanically–that is, by a combination of  instrumentation and the physicochemical action of root canal irrigants. Because infected root canals contain necrotic soft tissue remnants, bacteria-related proteins and biofilm, sodium hypochlorite (NaOCl) solutions have been recommended as the main irrigant for endodontic treatment. However, NaOCl solutions alone have not been shown to predictably clean the entire root canal system. EDTA is the most commonly used decalcifying agent for that purpose.

In the context of chemical root canal debridement, one key element has not been studied in detail: the effect of endodontic irrigants on the biofilm matrix. Previous studies have focused on the proportion of live vs dead bacteria in the biofilm after irrigation. However, research has suggested that NaOCl solutions are uniquely effective against oral biofilms and that they physically remove the biofilm structure, in contrast to other common disinfectants. It has also been claimed that EDTA has a disruptive effect on the biofilm matrix and that hydrogen peroxide (H202) can also reduce biofilm mass under specific experimental conditions. Investigating these claims was the focus of a study by Tawakoli et al from the University of Zurich, Switzerland.

A comparison of data from groups of 3 species of anaerobic biofilm treated with irrigants revealed that

    • NaOCl was the only irrigant that
      eradicated stainable matrix and
      bacteria in cultured biofilms after
      1 minute of exposure; this was
      superior in a comparison among all groups (p < .05).
    • EDTA also had some effect on the biofilm matrix.
    • H2O2 and chlorhexidine merely reduced bacterial cell volumes.


In this study, it appeared that NaOCl had several unique properties among common endodontic irrigants in its ability to chemically reduce biofilm-related matter. The NaOCl solution broke glycosidic bonds, dissolved glycoconjugates in the biofilm matrix and lysed bacterial cells.

Tawakoli PN , Ragnarsson R l , Rechenberg DK, et al. Effect of endodontic irrigants on biofilm matrix polysaccharides. Int Endod J 2016;doi:10.1111/iej.12604.<