N-Acetylcysteine Inhibits Growth and Eradicates Biofilm of Enterococcus faecalis

Introduction: The aims of this study were to evaluate the antibacterial and biofilm eradication efficacies of N-acetylcysteine (NAC) on Enterococcus faecalis. Methods: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of NAC on E. faecalis were determined. In addition, the ability of dentin powder to neutralize the antibacterial activity of NAC was examined. Calcium hydroxide, a commonly used intracanal medicament, was included as a comparison. The efficacy of NAC on E. faecalis biofilms was tested by exposure of 21-day old E. faecalis biofilms to NAC. Results: NAC was most bactericidal at pH 11 with MIC and MBC of 1.56 mg/mL and 12.5 mg/mL, respectively. Although preincubation of calcium hydroxide with dentin powder abolished its antibacterial effects, NAC completely killed E. faecalis regardless of dentin powder preincubation. In addition, prolonged incubation of NAC with dentin powder (up to 3 weeks) did not significantly reduce its antibacterial activity on E. faecalis. Furthermore, NAC also effectively eradicated E. faecalis biofilms. Conclusions: NAC was bactericidal against both the planktonic and biofilm forms of E. faecalis. This antibacterial property of NAC was unaffected by the presence of dentin. (J Endod 2012;38:81-85)