Antibacterial Efficacy of a Dispersion of Silver Nanoparticles in Citrate Medium for the Treatment of E. faecalis: an In Vitro Study

The purpose of this study was to measure the antibacterial efficacy of a dispersion of silver nanoparticles (AgNP) in a citrate medium tested in two E. faecalis strains. AgNP were synthesized, and AgNP citrate medium (AgNP-CM) dispersion was prepared at a concentration of 100 μg/mL. The antibacterial efficacy of AgNP-CM dispersion was evaluated over two E. faecalis strains: ATCC29212 and a wild strain collected from human necrotic teeth. 5% sodium hypochlorite (NaOCl) and sterile saline solution were used as positive and negative controls. 5 and 30-minute contact tests were conducted and each experimental group were replicated 10 times. After 24 hours of incubation, the Log CFU/mL were calculated. The AgNP obtained showed spherical shapes and had 30-60nm size. 5% NaOCl was able to completely eliminate both E. faecalis strains in all groups, showing a significant statistical difference when compared to AgNP-CM dispersion and negative control groups. AgNP-CM dispersion showed a statistically significant decrease in Log CFU/mL averages (p=0,0006) when compared to the sterile saline solution for the ATCC29212 strain during the 30-minute time. Between the 5-minute and 30-minute groups, a significant bacterial count decrease was also observed (p= 0,0128). The antibacterial efficacy of the dispersion was greater for the ATCC29212 strain than the wild strain, were the effect diminished. AgNP-CM dispersion showed a significantly lower antibacterial efficacy against E. faecalis than the 5% NaOCl at the tested times.