Antimicrobial activities of root canal sealers against Enterococcus Faecalis

Objective. The purpose of this study was evaluated the in vitro antibacterial activity of different root canal filling materials against E. faecalis, bacterial strain commonly found in endodontic infections. Materials and methods. The sealers evaluated in this study are the following: zinc oxide and eugenol cement (ZOE), Pulp Canal Sealer, Mineral Trioxide Aggregate (MTA), AH plus and EndoREZ sealer. The sealers were used in two different forms: A: freshly mixed sealers and B: disks solidified of the test materials (5mm diameter 3mm height). All test materials were prepared strictly in accordance with the manufacturer’s recommendation. The strain used for analysis was Enterococcus faecalis ATCC 29212. The test used to evaluate the antimicrobial activity is the diffusion method on Muller-Hinton agar (MH). 100 μl bacterial suspension of E. faecalis a turbidity of 0.5 on the McFarland scale, which corresponds to a concentration of 108 Colony Forming Units mL-1, were spread on agar plates. Materials in form of A and B were applied on the base layer. Positive and negative controls consisted of plates with and without inocula. All the plates were incubated at 37°C for 24, 48 and 72 hours. The plates were analyzed under reflected light and examined for zones of inhibition around each materials A and B as evidenced by lack of bacterial growth (clearing of agar) adjacent to each form of sealers. The zone of inhibition were measured in millimetres with a digital calliper. Six repetitions of the test were prepared for each experiment. The results were expressed as the mean and standard deviation and analyzed using Kruskal-Wallis test. Results. The positive controls showed bacterial growth, while the negative controls showed no bacterial growth. The reading after incubation provided the following data: freshly mixed ZOE, both tested shapes of Pulp Canal Sealer and AH plus all showed evidence of inhibition, but not statistically significant. Conversely, EndoREZ, MTA and ZOE disks solidified did not show any antimicrobial activity. Conclusions. E. faecalis is a facultative anaerobic gram-positive coccus that, despite making up a small proportion of the flora in untreated canals, is commonly detected in asymptomatic and in persistent and therapy resistant root canal treatment. Its prevalence in such infections ranges from 24% to 77%. This finding can be explained by different survival and virulence factors possessed by E. faecalis, including its ability to invade dentinal tubules and then to survive in an environment in which there are low available nutrients and in which commensality with other bacteria is minimal. E. faecalis is frequently used in in vitro tests because of its importance in endodontic infections and especially have been reported to be resistance to a wide range of antimicrobial agents.Based on the results and within the limitations of the methodology, it may be concluded that E. faecalis is a very resistant microorganism and that its growth is inhibited by the tested materials in this decreasing order: freshly mixed ZOE, Pulp Canal Sealer, AH plus. Moreover, for the tested strain, new sealer EndoREZ and conventional MTA are not a potent bacterial growth inhibitors.