Silver Proves Its Mettle Against Bacteria



It’s tiny but deadly. Enterococcus faecalis (E. faecalis) can cause life-threatening infections, especially in hospitals where it shows naturally high levels of antibiotic resistance. It’s frequently found in teeth treated for root canals in prevalence values ranging from 30% to 90%. In fact, these teeth are 9 times more likely to harbor it than cases of primary infections.

So what’s the best way to fight this microscopic monster? Researchers at Tehran University of Medical Sciences investigated the antibacterial characteristic and E. faecalis biofilm suppression effect of different vehicles of calcium hydroxide as intracanal medicaments in the short and long term. In their work, silver nanoparticles came out on top.

The researchers contaminated 54 single-root teeth with E. faecalis and randomly divided them into three experimental (n=16) and one control (n-6) group. Each group was exposed to various intracanal medicaments: calcium hydroxide with normal saline, calcium hydroxide with chlorhexidine, calclium hydroxide with silver nanoparticles suspension (AgNPs), and saline as the control group.

Cultures were made from each group after one week and one month, and the number of colonies was counted. A sample of each group was examined under electron microscope as well. The Kruskal-Wallis test served for inter-group comparisons, and the Mann Whitney test served for comparison between the two incubation periods.

Al the intracanal medicaments resulted in a significant decrease in the number of colonies compared to the control group in both incubation periods. After one week, the mixture of calcium hydroxide and AgNPs was the most effective medicament against E. faecalis (P < .05). No significant difference in antibacterial effect of the medicaments existed after the one-month incubation period (P > .05).

The researchers concluded that AgNPs was more effective on the E. faecalis biofilm than other tested vehicles in short-term medication. Clinically, they believe it has good potential to be used as an appropriate vehicle of calcium hydroxide to eliminate E. faecalis biofilm from human dentine in the short term.

The researchers included Seyyed Jalal Pourhashemi, Farzaneh Afkhami, Moona Sadegh, Yasaman Salehi, and Mohammad Javad Kharazi Fard. Their work is now available online from the Journal of Dentistry.