Antimicrobial Activity of Phytic Acid: a Potential Endodontic Irrigant

Objectives: Bacteria and associated biofilms play a key role in the failure of root canal treated teeth. Consequently, elimination of bacteria is an essential objective for root canal treatment. Despite debate over the benefits of smear layer removal in endodontics, the evidence in the literature generally favours removal. The most commonly used agent for this purpose is ethylenediaminetetraacetic acid (EDTA). EDTA is a synthetically produced agent and there are concerns about its overuse in root canal treatment.
Phytic acid (IP6) is a naturally occurring compound and reported to effectively remove the smear layer without host cell toxicity. Recently, we reported the antimicrobial effects of IP6 against planktonic cultures of the endodontic pathogen Enterococcus faecalis. However, the spectrum of IP6 activity and effectiveness against biofilm has yet to be elucidated. The aim of this study was to further evaluate IP6 against a range of bacterial species and their biofilms and compare it with EDTA.
Methods: A broth microdilution assay was used to measure the minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of IP6 and EDTA for planktonic cultures of Enterococcus faecalis, vancomycin resistant E. faecalis (VRE), Enterococcus faecium, Staphylococcus aureus, methicillin resistant S. aureus (MRSA), Pseudomonas aeruginosa and Escherichia coli. The minimum biofilm eradication concentrations (MBECs) of IP6 and EDTA were measured against biofilms developed in batch systems.
Results: IP6 (0.156%) was effective at inhibiting planktonic growth of test organisms and bactericidal activity occurred at 0.3125%. However, EDTA had no bactericidal effects except against P. aeruginosa and E. coli. IP6 eradicated biofilms of all test organisms at concentrations from 0.156% to 2.5%. EDTA only exhibited antibiofilm effects against E. coli.
Conclusions: IP6 has significant in vitro antimicrobial and antibiofilm activity compared with EDTA, which makes it a potentially attractive agent for use in endodontic treatment.