الفهرس 
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Abstract
Aim: to evaluate the effect of two different concentration of chitosan irrigation using two rotary systems (Revo S and One Shape) on smear layer removal during root canal treatment using scanning electron microscope. Materials and Methods: Forty of freshly extracted single canal with slightly straight fully mature roots human premolars were collected. After crown removal and working length determination, all samples were randomly divided into four main groups(n=10) according to rotary preparation system following the manufacturer’s instructions in crown-down manner and final chitosan irrigation concentration used. group I: Root canals preparation were performed using Revo- S rotary system up to master apical file(# 25/0.06) and then irrigated by 5ml of 0.2% chitosan solution for 3 min as final irrigation. group II:Root canals preparation were performed using One Shape single file (# 25/0.06) then irrigated using 5ml of 0.2% chitosan solution for 3 min as final irrigation. group III: Root canals prepared in the same manner as group I and then irrigated using 5ml of 0.37% chitosan solution for 3 min as final irrigation. group IV: Root canals prepared in the same manner as group II and then irrigated with 5ml 0.37% of chitosan solution for 3 min as final irrigation. During preparation and after change of each succeeding file, root canal irrigated with freshly prepared 5 mL of 2.5% sodium hypochlorite solution. Then, rinsed with 5 mL of distilled water. Finally, root canals were irrigated with final chitosan irrigation concentration as mentioned in groups. Samples were split longitudinally and examined by SEM analysis. Root canal cleanliness was qualitatively assessed at the coronal, middle, and apical regions of root halves . Kruskale Wallis test was used to compare between final irrigation solutions at each section and Manne Whitney U test was used for pairwise comparisons between groups whenever indicated. The significance level was set at P ≤ 0.05 . Results: It showed that there were no statistical significant differences between groups for smear layer covering the dentinal surfaces. When comparing different root levels, there were no statistical significant differences between coronal versus middle levels but between coronal versus apical and middle versus apical statistical significant differences were found. Conclusions: The four tested groups can effectively remove smear layer from coronal and middle levels compared to apical level. Using multiple file system (Revo-S files) is better than single file system (One Shape file) in removal of the smear layer of root canal. Increasing the concentration of chitosan to 0.37% promoted removal of the smear layer better than 0.2% of chitosan.