Title of manuscript: The Antimicrobial Efficacy of Nanoparticles Intracanal Medicaments Against Enterococcus Faecalis Biofilm.

Introduction: Bacteria can create biofilms that resist antimicrobials and cause persistent infections. With the introduction of nanotechnology in dentistry, intracanal medicaments could become more effective against bacteria. The purpose of this study was to compare the efficacy of normal sized calcium hydroxide (CaOH2) and chlorohexidine (CHX) against their nano counterparts in the elimination of Enterococcus faecalis biofilm. Methods: sixty-six human mandibular molars were contaminated with E. faecalis then treated with CaOH2, CaOH2 nanoparticles (np), CHX, CHX loaded by silver nanoparticles (Ag-np) and CHX loaded by chitosan nanoparticles (CH-np). Two periods of contact time were chosen ; two-days and seven-days. Comparison was based on colony forming units (CFU) and Scanning electron microscope (SEM) was used for biofilm confirmation and examining the effect of the medicaments on bacterial cells and biofilm. Results: CHX\Ag-np had the highest percentage reduction with a significant difference of