Antimicrobial activity of per acetic acid for trans-operative disinfection of endodontic files

Reducing the accumulation of microorganisms on an endodontic file during endodontic treatment is important to limit recontamination of the root canal and increase likelihood of successful treatment outcome. Objective: To compare the antimicrobial activity of peracetic acid (PA), isopropyl alcohol and acetone against a range of bacteria and also for disinfection of contaminated endodontic K-files. Material and Methods: Antimicrobial activities of PA, isopropyl alcohol and acetone were compared against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, vancomycin resistant E. faecalis (VRE) and meticillin resistant S. aureus (MRSA), using minimum bactericidal concentration (MBC) and time-kill assays. Test solutions at different exposure times (15 s and 30 s) were assessed for treatment of endodontic files acting as carriers of E. faecalis-contaminated dental debris. Results: All bacteria were susceptible to PA (MBC range 0.25-1%), acetone (MBC range 50-60%) and isopropyl alcohol (30-40%). Using a time-kill assay of the antimicrobials at the determined MBC, all test microorganisms, with the exception of E. faecalis (VRE) 7766 were killed after 15 s exposure. In the case of E. faecalis 7766, viable cells remained detectable after 120 s exposure to acetone. Testing disinfection of endodontic K-files, previously coated with dental debris containing E. faecalis, it was found that PA (2%) completely killed E. faecalis after 15 s exposure. However, even after 30 s exposure, isopropyl alcohol (80%) and acetone (80%) had limited disinfecting activity. Conclusion: Extrapolation of these results to clinical practice would suggest that PA would be the most effective agent for trans-operative disinfection of endodontic K-files during treatment of a single patient.