Purpose: This study was held to evaluate the antibacterial activity of two synthesized nanoparticles; Chitosan silver nanoparticle and poly (lactic co- glycolic acid) (PLGA) nanoparticles containing a photosensitizer and compare them with BioPure MTAD and Sodium Hypochlorite against a well-recognized resistant bacterium, Enterococcus faecalis. Material and Methods: Characterization of the nanoparticles was done using Ultraviolet–visible absorption (UV-Vis) spectroscopy, dynamic light scattering (DLS), Transmission electron microscope (TEM) and the Zeta potential measurement. For antibacterial assessment the minimum inhibitory concentration (MIC) that would exert antimicrobial properties and inhibits the growth of an organism was done using liquid Micro and Macro-dilution techniques. Secondary; the MIC of the Nanoparticles was tested for disinfecting experimentally infected root canals using two hundred and six freshly extracted human lower premolars that were mechanically prepared, autoclaved, filled with the E.faecalis standard microbial suspension, incubated for 1 week and 4 months and subjected to treatment. Confirmation of the production of biofilm was done using Environmental Scanning Electron Microscope (ESEM).Results: Results of the antibacterial efficacy of the tested Nanoparticles for disinfection of experimentally infected root canals showed insignificant difference between Ag/Cts, Ag/Cts irradiated by diode laser, MTAD and NaOCl; all showed the statistically significantly highest mean % reductions in bacterial counts which indicate the killing percentage of E.Faecalis. PLGA loaded with MB and irradiated by diode laser showed the statistically significantly lowest mean % reduction in bacterial counts. Conclusion: Treatment by Ag/Cts nanoparticles irradiated by diode laser, effectively destruct the biofilm of experimentally infected canal