Antimicrobial and anti-endotoxin activity of N-acetylcysteine, calcium hydroxide and their combination against Enterococcus faecalis, Escherichia coli and lipopolysaccharides

Abstract

Background: The management of endodontic infections is a complex challenge, mainly due to the involvement of diverse microorganisms and their by-products. This study aimed to evaluate the efficacy of N-acetylcysteine (NAC), calcium hydroxide (Ca(OH)₂), and their combined application as intracanal medications in combating <i>Enterococcus faecalis</i>, <i>Escherichia coli</i>, and lipopolysaccharides (LPS) from <i>E. coli</i>. Methods: A total of 60 single-rooted human teeth were carefully selected and divided into six groups. These tooth canals were deliberately exposed to <i>E. faecalis</i> (ATCC 29212) and <i>E. coli</i> (ATCC 25922) to induce biofilm formation. Subsequently, the specimens were treated with NAC, Ca(OH)₂, or a combination of both substances. Three samples of the root canals were collected at three moments: the first sample (S1) was to confirm the initial contamination, the second sample (S2) was immediately post-instrumentation, and the third sample (S3) was collected after the use of the intracanal medication. The antimicrobial efficacy of these intracanal medications was assessed by enumerating colony-forming units per milliliter (CFU/mL). In addition to this, the kinetic chromogenic Limulus Amebocyte Lysate (LAL) assay by Lonza was used to quantify LPS from <i>E. coli</i>. Data tested for normality; then, Kruskal-Wallis and Friedman tests were used, and Dunn's for multiple comparisons. Results: The findings of this study showed significant reductions in the microbial load of <i>E. faecalis</i> and <i>E. coli</i> by S3. Notably, there were no statistically significant differences among the treatment groups concerning these microorganisms. However, it was observed that only the combination of NAC and Ca(OH)₂ led to a noteworthy decrease in the quantity of <i>E. coli's</i> LPS after 7-days, demonstrating a statistically significant difference from the other treatment groups. NAC + Ca(OH)₂ combination, applied for a duration of 7-days, proved to be more suitable in reducing the presence of <i>E. faecalis</i>, <i>E. coli</i>, and LPS from <i>E. coli</i> within the context of endodontic infections.