Antimicrobial effect of phytic acid on Enterococcus faecalis

Objective One of the properties of an ideal root canal irrigant is the ability to eradicate Enterococcus faecalis which is one of the most resistant microorganisms encountered in persistent peri-radicular lesions. The aim of this study was to test the in vitro antibacterial effectiveness of a naturally occurring agent called phytic acid (IP6) against E. faecalis and compare it to the antibacterial activities of clinically used irrigants: sodium hypochlorite (NaOCl), ethylenediaminetetraacetic (EDTA), phosphoric acid (PA) and chlorhexidine (CHX). Design The antimicrobial activities of 5% IP6, 5% NaOCl, 18% EDTA, 37% PA and 2% CHX against E. faecalis were determined using disk diffusion test. Minimum inhibitory concentration (MIC) was calculated by broth macrodilution method. The minimal bactericidal concentration (MBC) was determined for the used agents by culturing the clear broth of MIC tests. Results The results of agar diffusion test showed statistically significant differences between the groups. PA showed a larger zone when compared to other tested materials (p< 0.05). There was no statistical significant difference between NaOCl, EDTA and CHX (p=0.098). IP6 showed the smallest zone of inhibition when compared to all groups (p< 0.05).The recorded MIC and MBC values for IP6 were 0.156% and 0.625%; respectively. The MIC and MBC values for PA were 0.578% and 4.6% and for NaOCl 0.093% and 0.375%, respectively. EDTA MIC value was 0.14 % but it showed no bactericidal activity. CHX was excluded from MIC test as immediate precipitation and turbidity occurred after mixing CHX with Mueller Hinton Broth. Conclusions Within the limitation of this study and despite that IP6 showed the smallest zone of inhibition in agar diffusion test, the results of MIC and MBC indicated that IP6 exhibits in vitro antibacterial effect against E. faecalis at low concentrations.