Antimicrobial efficacy of endodontic irrigation solutions against planktonic microorganisms and dual-species biofilm

ObjectiveTo compare the antimicrobial effect of different irrigation solutions against Enterococcus faecalis (E. faecalis) and Streptococcus mutans (S. mutans) planktonic microorganisms and dual-species biofilm within the root canal.Materials and methodsForty three extracted human single-rooted teeth (18–25 years old) were selected and decoronated. The root canals were prepared to a master apical size 40 using hand K-files with distilled water irrigation. Roots were sterilized, microbial suspension of mixed culture of the tested microorganisms were inoculated into canals and incubated for 48 h. Three randomly chosen teeth were used to check up root infection, the remaining forty infected root canals were divided equally into 4 groups according to the irrigant solutions used. Group A: sterile distilled water; Group B: 5.25% Sodium Hypochlorite (NaOCl); Group C: 2% Chlorhexidine (CHX); Group D: 200 mg/mL N-Acetylcysteine (NAC) solution. Finally, the canals were washed with saline. The first microbiological sampling for planktonic bacteria was taken from root canal lumen and the number of CFU of tested organisms was counted. Each root canal was then split longitudinally, and a 4-mm-long mid-part of one half was cut, sterilized and inoculated with the mixed microbial suspension for 48 h. Specimens of each group were immersed in 5 ml of tested irrigation solution for 5 min. The proportions of dead bacterial cells in the biofilm were assessed by CLSM.ResultsBoth planktonic bacteria were more sensitive to NAC solution recording significantly the lowest mean CFU values. S. mutans was statistically more sensitive to NaOCl irrigation compared to E. faecalis. CLSM showed significantly more proportion of dead cells in dual-species biofilm when NAC irrigation solution was used.ConclusionNAC solution can be considered as a potential alternative irrigation solution in root canal infections because of its antimicrobial efficacy against both S. mutans and E. faecalis planktonic bacteria and dual-species biofilm.