الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Endodontic infections are mostly biofilm-based infections caused by microbial consortium, in which E faecalis plays a pivotal role both in primary and secondary infections, whether the biofilm is intraradicular, extraradicular, periapical, or biomaterial-centered. Chemo-mechanical canal preparation plays a central role in biofilm eradication. However, conventional antimicrobial strategies are insufficient to completely eradicate the microbial biofilms due to increased antimicrobial resistance; especially among the biofilm. Thus, the need for innovative methods to combat the microbial threat is increasing. Among the recent antimicrobials, research about nano-sized materials is rapidly expanding. Among other advantages, NP-based irrigants have smaller particle size and thus high surface area-to-mass ratio, which potentiates its antibacterial and anti-biofilm properties. CHX and AgNPs showed promising antibiofilm properties against E faecalis. Therefore, it was thought that it would be of value to evaluate the effect of the combination between CHX and AgNPs on E faecalis biofilm compared to the effect of CHX alone and AgNPs alone.
45 root specimens were chemo-mechanically prepared and autoclaved. Then the specimens were incubated in BHI broth for 24 hours at 37˚C to ensure their sterility. A pure strain of E faecalis was incubated in BHI broth at 37˚C for 24 hours20,72. Then the bacterial suspension was taken and inoculated on BHI agar plate at 37˚C for 24 hours72. The bacterial cells were resuspended in sterile saline to reach a final concentration of 3 x 108 cells/ml adjusted to No. 1 MacFarland turbidity standard20,71,72.
After discarding the sterile broth, 3 ml of the bacterial suspension mixed with BHI broth was used to infect the prepared canal under anaerobic conditions and the specimens were incubated in BHI broth at 37˚C for 6 weeks38,48,56; a fresh broth adjusted to No. 1 MacFarland turbidity standard was replenished every 72 hours to ensure cell viability, continuous supply of nutrients and wash out of unattached bacterial cells and bacterial by-products20,71,72.
After 6 weeks, 5 random specimens were investigated via SEM to verify biofilm formation. The remaining 40 specimens were then randomly divided into the 4 test groups; group I: CHX-loaded AgNPs, group II: 100 ppm AgNPs, group III: CHX, and group IV: sterile saline. All irrigants were introduced inside the canals using a side-vented, sterile needle 1 mm shorter than the working length with flow rate of 3mm/min. A fresh solution was introduced at 1, 3, and 10 minutes58. The AgNPs solution was prepared via the chemical reduction method where (NaBH4) was used as a mild reducing agent. CHX-loaded AgNPs solution was prepared via electrostatic attraction method.