Evaluation of antibacterial activity of silver nanoparticles activated by photodynamic method in infected root canals

Objectives: The aim of present study was to investigate the effect of antibacterial activity of light application on the combination of a photosensitizer agent, Toluidine Blue O (TBO) and a nano agent, silver nanoparticles (AgNPs) on a 3-week old mature Enterococcus faecalis (E. faecalis) biofilm formed experimentally on extracted human teeth. Materials and Methods: In this study, concentration at 20 ppm TBO and 10 ppm AgNP that the provided highest antibacterial effect against E. faecalis on TBO/AgNP combination was used according to preliminary study. After instrumentation, 130 human single-root, straight-canal mandibular premolars teeth that a standard length had adjusted to 13 mm contaminated with E. faecalis bacteria and experimental procedures were conducted against 21-day old mature biofilm. Teeth were randomly divided into 5 main experimental groups (n = 20) and sodium hypochlorite (NaOCl) (n=10) and saline solution (n=10). Then, these main groups were divided into 2 subgroups (30 and 60 sec) (n = 10). Experimental procedures consists of the following groups: G1; Photodynamic therapy (PDT) (TBO/Light), G2; AgNP, G3; TBO/AgNP, G4; AgNP/Light, G5; TBO/AgNP/Light. Irrigation with 2 mL of 2.5% NaOCl for 1 min and irrigation with 2 mL of 0.9% saline solution for 1 min serve positive and negative control, respectively. Kolmogorov Smirnov, Oneway ANOVA and Tukey HSD tests were used to carry out statistical analysis of the study's data. After Bonferroni correction, p<0.004 was taken as the statistical significance. Results: NaOCl group provided a bacterial reduction, which was higher than all other groups in a statistically significant manner, and was the group that displayed the highest antibacterial activity (p<0.004). Light application on the TBO/AgNPs combination was the group that provided the highest bacterial reduction after NaOCl. Conclusions: Photoactivation on TBO/AgNP combination led to increase in effect of PDT and this group was the most successful group after NaOCl. The use of nano agents as carriers plays an important role in increasing the efficiency of FDT.