الفهرس 
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Abstract
Irrigation is a pivotal step in the cleaning of the root canal complex and the eradication of resistant bacterial biofilm as well as elimination of toxins within the root dentin. Ensuring the cleanliness of root canal comes at a cost of altering the physical and mechanical properties of the dentinal microstructure. Sodium hypochlorite, though an efficient antibacterial irrigant and an organic tissue dissolver, is suggested to change the nature of dentin especially the calcium phosphorous ratio. Nanotechnology is considered a new emerging wave in developing materials that can aid in the antibacterial activity of irrigants. Nanoparticles in suspension especially chitosan and silver nano particles have been suggested as effective irrigations for the endodontic procedure of cleaning the infected root canal system. This study aims to test the efficacy of newly introduced nano particles irrigations in comparison with the golden standard irrigation regarding their antibacterial effect and the altering of dentin composition within the root canal dentin.
A total of sixty five single rooted human teeth were collected after being freshly extracted. Each tooth was accessed and prepared using one shape rotary files and then manual step back technique was performed at the apical portion to a size of 40#. The teeth were then divided into: antibacterial test group (45 teeth) and dentin composition test group (20 teeth).
For Evaluation of Antibacterial effect: A number of 45 prepared tooth was inoculated with E.faecalis bacteria for 21 days to develop biofilm, which was confirmed using Scanning electron microscope. After that, the teeth were divided into 5 groups according to the irrigant used: group A sodium hypochlorite 5.25% (10 teeth), group B Silver Nano Particles 80 ml suspension 2% (10 teeth), group C chitosan nano particles 80 ml suspension 2% (10 teeth), group D positive Control (10 teeth) and group D negative control (5 teeth). Each tooth was irrigated with the specified irrigant for a time of 2 minutes while being activated by manual agitation protocol using k files (10-15#). Each tooth was then irrigated with saline solution and a paper point sample was collected from each saline solution. For evaluation of antibacterial effect; Each paper point collected was tested for bacterial evaluation using colony forming unit test. Colony forming unit Tests were statistically measured using one way analysis of variance (ANOVA) test, followed by Tukey’s post hoc test.
For Evaluation of Dentin composition effect: A number of 20 prepared teeth were first divided into 4 groups according to the irrigant used: group A silver nano particles ( 5 teeth ) group B sodium hypochlorite ( 5 teeth) group C chitosan nano particles ( 5 teeth) and group D negative Control ( 5 teeth) . Each group was then irrigated with each specific irrigant and activated as mentioned before. After the irrigation protocol, each tooth was sectioned longitudinally into two halves using diamond discs. One half of each tooth was selected according to a minimal thickness of 2 mm in order to be appropriate for the inorganic analysis using energy dispersive x-ray (EDX). Changes in dentin structure were done by recording the changes in the calcium phosphorous ratio at single spots inside the root canal in the apical and middle areas of each root. One-way Analysis of Variance (ANOVA) was used to compare between the three groups. Bonferroni’s post-hoc test was used for pair-wise comparisons when ANOVA test is significant.
Regarding the antibacterial effect, Bacterial growth was observed in only 70% of Sodium hypochlorite group samples and in only 90% of silver nano group samples as well as chitosan nano group respectively.
Negative control showed no bacterial growth. A significantly higher mean value recorded in positive control. Among the study groups, chitosan (nano particles) recorded the highest mean value followed by silver (nano particles) with the least mean value recorded in sodium hypochlorite with no significant difference between these 3 groups.
Regarding the dentin composition effect; sodium hypochlorite recorded the highest mean calcium to phosphorous weight followed by silver nano particles while chitosan showed the lowest mean calcium to phosphorous weight. In comparison between calcium phosphorous levels; there was no significant differences between the three groups.
CONCLUSIONS
Based on the results of the present study:
1- Silver Nano particles irrigation and Chitosan Nano particles irrigation showed lower antibacterial effects against E. faecalis biofilm than sodium hypochlorite irrigation
2- Similar effect on dentin composition was noticed among the three irrigants used Silver Nano particles irrigation, Chitosan Nano particles irrigation and Sodium Hypochlorite irrigation.
3- Chitosan Nano Particles irrigation and Silver Nano particles irrigation showed no advantage to Sodium hypochlorite regarding; antibacterial effect nor the effect on dentin composition.