Antibacterial properties of silver nanoparticles as a root canal irrigant against Enterococcus faecalis biofilm and infected dentinal tubules

Abstract

Aim

To evaluate the antimicrobial action of an irrigant containing silver nanoparticles in aqueous vehicle (AgNp), sodium hypochlorite and chlorhexidine against Enterococcus faecalis biofilm and infected dentinal tubules.

Methodology

Bovine dentine blocks were used for E. faecalis biofilm development for 21 days and irrigated with 94 ppm AgNp solution, 2.5% NaOCl and 2% Chlorhexidine for 5, 15 and 30 minutes. For infection of dentinal tubules with E. faecalis, dentine specimens from bovine incisors were submitted to a contamination protocol over five days, with 8 centrifugation cycles on every alternate day, and irrigated with the same solutions and time intervals used for the biofilm. The specimens were stained with the Live/Dead technique and evaluated using a confocal laser scanning microscope (CLSM). The bioImage_L software was used for measurement of the total biovolume of biofilm in μm³ and percentage of viable bacteria (green cells) in biofilm and in dentinal tubules found after the irrigation. Statistical analyses were performed using Kruskal-Wallis and Dunn tests for quantification of viable cells in biofilm, Friedman test for comparisons of viable bacteria in dentinal tubules in different areas of the root canal and Mann-Whitney U-test to compare the action of the irrigants between the two methods (P < 0.05).

Results

The AgNp solution eliminated fewer bacteria, but showed more ability to dissolve biofilm compared with chlorhexidine (P < 0.05). NaOCl had the greatest antimicrobial activity and biofilm dissolution capacity. AgNp solution had less antimicrobial action in infected dentinal tubules compared with NaOCl (P < 0.05). The AgNp solution after 5 minutes was more effective in eliminating planktonic bacteria in dentinal tubules than in biofilm, but at 30 minutes fewer viable bacteria were observed in the biofilm compared with intratubular dentine (P < 0.05).

Conclusions

AgNp irrigant was not as effective against E. faecalis as solutions commonly used in root canal treatment. NaOCl is appropriate as an irrigant because it was effective in disrupting biofilm and in eliminating bacteria in biofilms and in dentinal tubules.

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