Antimicrobial Effect of Different Root Canal Medicaments on Enterococcus Faecalis: in vitro Comparative Study

Introduction: Enterococcus faecalis (E. faecalis) is a microorganism commonly detected in persistent endodontic infections. Eradication of this organism from an infected root canal remains a significant clinical challenge for modern endodontic treatment. So, this in vitro study was conducted to compare antimicrobial effect of some root canal medicaments on E. faecalis. Materials/Methods: A total of 50 E. faecalis strains (49 strains were selected randomly from positive cultures together with a standard E. faecalis strain ATCC 29212) were used in the study. Inoculum for each bacterial strain was prepared in a turbidity of 0.5 on McFarland scale. The prepared discs of the three intracanal medicaments; chlorhexidine, diapex and diclofenac; together with readymade discs of amoxicillin and doxycycline were distributed on blood agar and Mueller-Hinton agar plates inoculated with an E. faecalis suspension previously prepared. Antimicrobial activity was assessed by measuring the diameters of the zones of growth inhibition surround the discs after incubation at 37°C for 24 hours and then after 48 hours. Results: All strains (100%) were sensitive to chlorhexidine even though strains that showed resistance to one or both of antibiotic used (amoxicillin, doxycycline). On the other hand, all strains (100%) were resistant to diapex and diclofenac even standard strain. Sixty eight percent of the tested strains were sensitive to doxycyline and 44% of them were sensitive to amoxicillin. Conclusion: Under the conditions of this study, chlorhexidine is very effective against E. faecalis and can be considered as the most powerful root canal medicament compared to other intracanal medicaments tested. Controversially, no zones of inhibition were detected around diapex and diclofenac.