الفهرس 
Title: Evaluation of the effect of chitosan versus sodium hypochlorite and ethylene diamine tetra acetate on the microbial content and cleanliness of the root canal
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Abstract
The aim of this study was to evaluate and compare the antibacterial activity and canal cleaning efficiency of 0.2% chitosan, 2.6% NaOCl and 2.6% NaOCl followed by 17% EDTA. For the evaluation of the antibacterial activity, 70 roots were vertically mounted in Eppendorf tubes using dental stone with the cervical portion facing upwards. Root canals were inoculated with E. faecalis ATCC29212 (except for 14 specimens which served as the negative control group) and incubated for three weeks at 37{u00B0}C under aerobic conditions in a humid environment and the culture medium was replenished every four days. Specimens were, then, divided into four groups of 14 specimens each according to the irrigating solution used as follows: 0.2% chitosan, 2.6% NaOCl, 2.6% NaOCl followed by 17% EDTA and 0.9% saline (positive control). Five mL of each solution was used for 3 min; except for EDTA which was used for 1 min. Irrigation was carried out using a 29-gauge needle. Microbial sampling from the root canal was carried out using H-file #40 followed by three paper points #50. Samples were serially diluted and aliquots were plated on agar plates, which were incubated for 48 h. The grown E. faecalis colonies were automatically counted using the OpenCFU software. For the evaluation of the canal cleaning efficiency, 40 specimens were divided into four groups according to the final irrigating solution used as follows: 0.2% chitosan, 2.6% NaOCl, 2.6% NaOCl/17% EDTA and a control group irrigated with 0.9% saline (n=10). Roots were longitudinally split into two halves, the half which best represented the root canal was used for SEM analysis and the other half was discarded. Micrographs were taken at fixed lengths in the apical, middle and coronal thirds. In each third, two sites were imaged and at each site, two micrographs were taken; at 1000x and 2000x magnifications for debris and smear layer evaluation respectively. Three, calibrated, blind examiners assessed the micrographs separately following the scoring system suggested by Hülsmann et al. (1997). Ten micrographs served as visual reference standards throughout the course of the evaluation