In vitro evaluation of N-acetylcysteine, calcium hydroxide, chlorhexidine digluconate and their combinations effect against five dental obligate anaerobic bacteria

Background This study aimed to evaluate the antibacterial action of N-acetylcysteine (NAC), calcium hydroxide Ca(OH) 2 , chlorhexidine digluconate (CHX), and their combinations against five obligate anaerobic bacteria including Fusobacterium nucleatum, Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia , and Parvimonas micra in planktonic and biofilm forms. Methods Eight experimental groups were evaluated in this study including saline solution (SS) (control group), Ca(OH) 2 , CHX, NAC, NAC + Ca(OH) 2 , NAC + CHX, Ca(OH) 2 + CHX, and NAC + Ca(OH) 2 + CHX. The anti-planktonic evaluation was performed by determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) following Clinical and Laboratory Standards Institute guidelines (CLSI M11). The antibiofilm was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet (CV) assays. Data were analyzed statistically considering a significant level of ( α ≤ 0.05). Results It was found that the MIC and MBC values of the tested intracanal medications ranged from 1.95–500 mg/mL. MTT and CV assays showed significant, species-dependent antibiofilm activity. CHX was most effective against F. nucleatum ; NAC-based medications, especially combined with Ca(OH) 2 and/or CHX, were superior against P. endodontalis, P. intermedia , and P. micra . Ca(OH) 2 -containing groups were particularly effective against P. gingivalis . Therefore, NAC + Ca(OH) 2 and NAC + Ca(OH) 2 + CHX can be considered as effective combinations of intracanal medication against different obligate anaerobic bacteria.