Evaluation of the antibacterial efficacy of silver nanoparticles against Enterococcus faecalis biofilm.
BACKGROUND
The purpose of this study was to evaluate the antibacterial efficacy of silver nanoparticles (AgNPs) as an irrigant or medicament against Enterococcus faecalis biofilms formed on root dentin.


METHODS
Dentin sections were inoculated with E. faecalis for 4 weeks to establish a standard monospecies biofilm model. These biofilms were tested in 2 stages. In stage 1, the biofilms were irrigated with 0.1% AgNP solution, 2% sodium hypochlorite, and sterile saline for 2 minutes, respectively. In stage 2, the biofilms were treated with AgNP gel (0.02% and 0.01%) and calcium hydroxide for 7 days. The ultrastructure of one half of the specimens from each group was evaluated by using scanning electron microscopy, whereas the structure and distribution of viable bacteria of the other half of the specimens were assessed with confocal laser scanning microscopy combined with viability staining.


RESULTS
Syringe irrigation with 0.1% AgNP solution did not disrupt the biofilm structure, and the proportion of viable bacteria in the biofilm structures was not different from that of the saline group (P > .05) but was less than that of the control group (P < .05). The biofilms treated with 0.02% AgNP gel as medicament significantly disrupted the structural integrity of the biofilm and resulted in the least number of post-treatment residual viable E. faecalis cells compared with 0.01% AgNP gel and calcium hydroxide groups (P < .05).


CONCLUSIONS
The findings from this study suggested that the antibiofilm efficacy of AgNPs depends on the mode of application. AgNPs as a medicament and not as an irrigant showed potential to eliminate residual bacterial biofilms during root canal disinfection.
State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China.
Daming
D
Wu
State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China.
Wei
W
Fan
Disciplines of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada.
Anil
A
Kishen
Department of Endodontics, Baylor College of Dentistry, Texas A and M University System Health Science Center, Dallas, Texas.
James L
JL
Gutmann
State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China. Electronic address: b.fan@163.com.
Bing
B
Fan
D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002126:Calcium Hydroxide / Q000494:pharmacology; D003804:Dentin / Q000382:microbiology; D013293:Enterococcus faecalis / Q000187:drug effects*; D005456:Fluorescent Dyes; D005782:Gels; D006801:Humans; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000008:administration & dosage / Q000627:therapeutic use*; D050296:Microbial Viability / Q000187:drug effects; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D012388:Root Canal Irrigants / Q000008:administration & dosage / Q000494:pharmacology; D012834:Silver / Q000008:administration & dosage / Q000494:pharmacology*; D012973:Sodium Hypochlorite / Q000494:pharmacology; D012996:Solutions; D014092:Tooth Root / Q000382:microbiology
D000900:Anti-Bacterial Agents; D005456:Fluorescent Dyes; D005782:Gels; D012388:Root Canal Irrigants; D012996:Solutions; D012834:Silver; D012973:Sodium Hypochlorite; D002126:Calcium Hydroxide
Antibacterial; Enterococcus faecalis; biofilms; silver nanoparticles