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      Effectiveness of N-acetyl cysteine, 2% chlorhexidine, and their combination as intracanal medicaments on Enterococcus faecalis biofilm

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          The purpose of this study was to evaluate the antibacterial efficacies of 2% chlorhexidine (CHX), N-acetyl cysteine (NAC) and assess their synergistic or antagonist action as intracanal medicament.

          Materials and Methods:

          Agar diffusion test was performed with 2% CHX, NAC, and their combination against E. faecalis planktonic cells. The diameters of the zones of bacterial inhibition were measured and recorded for each solution. The assay was further extended to 2 weeks old E. faecalis dentinal biofilm. Sixteen freshly extracted teeth were vertically sectioned into two halves resulting in a total of 32 samples. The samples were inoculated with bacterial suspension and incubated at 37°C for 2 weeks for biofilm formation. The samples were then divided into four experimental groups with 8 samples in each group. The samples were gently washed in saline and placed in culture wells containing the test solutions, i.e., 2% CHX, NAC, a combination of 2% CHX and NAC in 1:1 ratio, and a control group containing saline. The biofilm formed on the root canal surface were removed with a sterile scalpel and inoculated on blood agar plates to check for the formation of E. faecalis colonies.

          Statistical Analysis:

          For agar diffusion test, data were analyzed statistically using one-way analysis of variance and then by post-hoc Scheffe's test to compare the antimicrobial efficacy between the groups. Statistical analysis was not done for the cultures obtained from the biofilm as there was no growth in all the three test groups except the control group, i.e., saline.


          In agar diffusion test, among the three groups tested, 2% CHX and NAC showed almost equal zones of inhibition whereas maximum inhibition was shown by a combination of NAC and 2% CHX suggesting a synergistic action. The results obtained were highly significant ( P < 0.001) for the combination of medicament when compared to individual test group. In culture analysis, which was done for the biofilm, no growth was observed in all the three test groups. The results obtained were biologically significant but statistically insignificant.


          NAC has almost equal antimicrobial property as 2% CHX whereas their combination showed a synergistic action.

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          Most cited references 25

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          Enterococcus faecalis--a mechanism for its role in endodontic failure.

           Nick Love (2001)
          The aim of this study was to identify a possible mechanism that would explain how E. faecalis could survive and grow within dentinal tubules and reinfect an obturated root canal. Cells of Streptococcus gordonii DL1, Streptococcus mutans NG8, or E. faecalis JH2-2 were grown in brain heart infusion broth containing various amounts of human serum for 56 days. The ability of the three species to invade dentine and bind to immobilized type I collagen in the presence of human serum was assessed by dentine invasion and microtitre well experiments. All three species remained viable over the period of the experiment when grown in human serum. Cells of all three bacteria were able to invade dentine and bind to immobilized collagen. Both of these properties were inhibited by the presence of collagen in the cell solution. Human serum inhibited dentine invasion and collagen adhesion by S. gordonii DL1 and S. mutans NG8, whilst dentine invasion by E. faecalis JH2-2 was reduced in the presence of serum, but not inhibited, and binding to collagen was enhanced. It is postulated that a virulence factor of E. faecalis in failed endodontically treated teeth may be related to the ability of E. faecalis cells to maintain the capability to invade dentinal tubules and adhere to collagen in the presence of human serum.
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            Formation and transfer of disulphide bonds in living cells.

            Protein disulphide bonds are formed in the endoplasmic reticulum of eukaryotic cells and the periplasmic space of prokaryotic cells. The main pathways that catalyse the formation of protein disulphide bonds in prokaryotes and eukaryotes are remarkably similar, and they share several mechanistic features. The recent identification of new redox-active proteins in humans and yeast that mechanistically parallel the more established redox-active enzymes indicates that there might be further uncharacterized redox pathways throughout the cell.
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              • Article: not found

              Mechanisms involved in the resistance of Enterococcus faecalis to calcium hydroxide.

              This study sought to clarify the mechanisms that enable E. faecalis to survive the high pH of calcium hydroxide. E. faecalis strain JH2-2 was exposed to sublethal concentrations of calcium hydroxide, with and without various pretreatments. Blocking agents were added to determine the role of stress-induced protein synthesis and the cell wall-associated proton pump. E. faecalis was resistant to calcium hydroxide at a pH of 11.1, but not pH 11.5. Pre-treatment with calcium hydroxide pH 10.3 induced no tolerance to further exposure at pH 11.5. No difference in cell survival was observed when protein synthesis was blocked during stress induction, however, addition of a proton pump inhibitor resulted in a dramatic reduction of cell viability of E. faecalis in calcium hydroxide. Survival of E. faecalis in calcium hydroxide appears to be unrelated to stress induced protein synthesis, but a functioning proton pump is critical for survival of E. faecalis at high pH.

                Author and article information

                J Conserv Dent
                J Conserv Dent
                Journal of Conservative Dentistry : JCD
                Medknow Publications & Media Pvt Ltd (India )
                Jan-Feb 2016
                : 19
                : 1
                : 17-20
                Department of Conservative and Endodontics, SVS Institute of Dental Sciences, Mahabubnagar, Telangana, India
                Author notes
                Address for correspondence: Dr. Udayakumar Palaniswamy, Department of Conservative and Endodontics, SVS Institute of Dental Sciences, Appanapalli, Mahabubnagar, Telangana, India. E-mail: udayadent@ 123456yahoo.com
                Copyright: © Journal of Conservative Dentistry

                This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

                Original Article


                agar diffusion test, 2% chlorhexidine, e. faecalis dentinal biofilm, n-acetyl cysteine


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