Irrigant Solutions on Bacterial Biofilms: a Confocal Microscopy Analysis

Objective: This study evaluated in vitro the effectiveness of two endodontic irrigants and their association on disinfection of bovine root canals infected with Enterococcus faecalis by Confocal Laser Scanning Microscope (CLSM). Methods: Twenty-one bovine incisors were selected and inoculated in a monoculture of Enterococcus faecalis for 21 days. After this period, the teeth were randomly divided into three test groups (n = 5) according to the irrigant: Group 1 (G1) - 2.5% sodium hypochlorite (NaOCl), group 2 (G2) - 2% chlorhexidine (CHX) gel, group 3 (G3) - 2,5% NaOCl + 2% CHX gel, and two control groups (CG) (n = 3): negative control group (NCG) - sterile and positive control group (PCG) - infected. The samples were stained with SYTO9 and propidium iodide and subjected to analysis by CLSM. Scores were standardized according to the bacterial viability to tabulate the results: 0 = ≤ 25% of viable bacteria, 1 = > 25% and < 50%, 2 = 50%, 3 = > 50% and < 75% and 4 = ≥ 75%. Results: The PCG showed scores 2 and 3; NCG exhibited score 0 in all samples (no viable bacteria); although sodium hypochlorite has shown great efficiency in removing the biofilm, all remaining bacteria were viable (score 4); Chlorhexidine group presented score 3, however with less cleaning potential when compared to G1; the irrigants association was rated with scores between 2 and 3, presenting a minimal bacterial quantity, similar to G1, and a shorter number of viable microorganisms. Conclusion: The association between sodium hypochlorite and chlorhexidine was more effective against Enterococcus faecalis than the isolated solutions.