Comparative Evaluation of Antibacterial Efficacy of Silver and Cadmium Nanoparticles and Calcium Hydroxide against Enterococcus faecalis Biofilm

Abstract

The purpose of this study was to evaluate and compare the antibacterial efficacy of calcium hydroxide medicament, silver (AgNPs) and cadmium nanoparticles (CdSNPs) as medicament against the biofilms of Enterococcus faecalis on dentin sections. E. faecalis is commonly detected in asymptomatic and persistent endodontic infections. Twenty standard size dentin sections were prepared. E. faecalis was inoculated on these dentin sections for four weeks to form the bacterial biofilm. Twenty dentin sections were segregated into four different groups with five specimens in each group. Group I was kept as control group, and antibacterial efficacy was tested by treating biofilms with Ca(OH) 2 medicament, 0.02% AgNP and CdSNP gels for 7 days. The ultrastructure of biofilms from each group was examined under scanning electron microscope and was visually evaluated and compared for different groups. Ca(OH)2 exhibited a slight disruption of E. faecalis biofilm. Both AgNP and CdSNP medicaments disrupted E. faecalis biofilm effectively after 7 days of inoculation. AgNPs disrupted the biofilm more effectively than CdSNPs. Biofilms in control group, which was irrigated with saline, did not show any disruption of biofilm, which could be seen as homogenous layer over most of dentin sections. This study suggests that both AgNP and CdNP gels are effective against E. faecalis and can be used as a medicament to eliminate residual bacterial biofilms during root canal disinfection. AgNP medicament is more effective than CdNP, whereas Ca(OH) 2 is not effective against E. faecalis biofilms. Incomplete clearance and the development of antibiotic resistance in E. faecalis are the important factors for failure of root canal treatment. When cationic nanoparticles are introduced for the treatment of biofilms, it can interact with both extracellular polymeric substances and bacterial cells. The initial electrostatic attraction between positively charged nanoparticles and negatively charged bacterial surface leads to bacterial killing via the production of reactive oxygen species. Metal nanoparticles that are effective against E. faecalis have a significant potential role in the prevention and treatment of such cases, as bacteria do not develop resistance against metal nanoparticles.