الفهرس 
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Abstract
This in vitro study was conducted to compare the antibacterial efficacy of Chlorhexidine, Silver Nanoparticles and their combination as root canal irrigants against E. faecalis biofilm by counting colony forming units per milliliter as well as their effect on root canal filling adaptation by evaluating the presence of gaps between the filling material and the root canal dentine under scanning electron microscope.
Sixty mandibular premolars with single roots and single root canals were included in the study. All teeth were Instrumented using Rotary ProTaper files up to size F4. Irrigation was done using 2.5% NaOCl during mechanical instrumentation and finally the canals were flushed with sterile saline. Teeth were then divided into two main groups of thirty teeth.
group 1 was used to evaluate the antibacterial efficacy. Teeth were sterilized then infected with E. faecalis and incubated for 21 days to allow biofilm formation and maturation, and then teeth were randomly divided into 3 groups of 10 teeth according to the irrigant used. A tooth from each group was longitudinally sectioned and transferred for scanning electron microscope evaluation to confirm biofilm formation. Each tooth was flushed with 5 ml of the corresponding irrigant according to its subgroup; samples from root canals were collected using sterile paper points before and after irrigation, transferred to microbiology labs to count Colony forming units per milliliter.
group 2 was used to evaluate the effect of different irrigating solutions on root canal filling adaptation. Teeth were randomly divided into 3 groups of 10 teeth. Each tooth was flushed with 5ml of the corresponding irrigant according to its subgroup and obturated with cold lateral compaction technique, then left for one week to allow complete setting of the resin sealer. After that teeth were sectioned at apical and middle parts to be evaluated for interfacial adaptation under Scanning Electron Microscope. Evaluation was done both qualitatively by evaluating the overall percentage of gaps in each section and quantitatively by measuring maximum gap distance between the root canal filling and root dentin.
All data including number of CFU/ml before and after irrigation and the filling adaptation scores were statistically analyzed, results showed significant reduction in the colony count with all irrigants. The Chlorhexidine/ Silver Nanoparticles combination was significantly better than Chlorhexidine alone and Silver Nanoparticles alone. There was no statistically significant difference in root canal filling adaptation scores between the three groups, the Chlorhexidine/Silver Nanoparticles combination had slightly better adaptation at both apical and middle sections but the difference wasn’t statistically significant. A statistically significant difference in the maximum gap difference was found between the three groups with the least gap difference in the CHX/AgNPs group.
Within the limits of this study, it can be concluded that:
1- Irrigation with Chlorhexidine/ Silver Nanoparticles combination had a great effect on E. faecalis elimination.
2- Irrigation with Chlorhexidine/ Silver Nanoparticles combination had no significant effect on root canal filling adaptation.
3- Irrigation with Chlorhexidine solution didn’t improve the root canal filling adaptation.
Recommendations
• Further clinical studies are required to test the antimicrobial efficacy of Chlorhexidine/ Silver Nanoparticles combination against E. faecalis in vivo.
• Further studies are required to test the antimicrobial efficacy of Chlorhexidine/ Silver Nanoparticles combination against E. faecalis using different methods of evaluation.
• Further studies are required to test the antimicrobial efficacy of Chlorhexidine/ Silver Nanoparticles combination against different bacterial strains and multispecies biofilm.