الفهرس 
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Abstract
The aim of this study is to compare three systems with different kinematics Protaper Next, Wave one Gold and One Curve in regard to the cleaning and shaping of root canal system.
Cleaning ability of the file systems was evaluated by the amount of colony forming units before and after instrumentation using Enterococcus faecalis as the bacterial isolate. The shaping capabilities of the root canal file systems were evaluated with the amount of change in the canal curvature and the amount of transportation before and after instrumentation, and this is done by comparing pre and post instrumentation scans done by CBCT images at three different levels (3mm, 6mm and 9mm levels representing apical, middle and coronal third respectively).
Sixty-five human extracted mandibular first molar teeth were selected for this study. Teeth were de-coronated leveling the occlusal table at cement-enamel junction using a diamond bur and removal of the distal root. then CBCT scans were taken with the teeth embedded in a silicone mold to make sure that the images are standardized and reproducible. After the initial scans, the samples were infected with Enterococcus faecalis in order to test the cleanliness of the canal following the use of the file systems presented in the study.
The specimens were classified into three experimental groups (n=15), along with one positive control group (n=15) and one negative control group (n=5). The results were tabulated and statistically analyzed.
In regard to bacterial reduction, WOG has showed the lowest values of bacterial reduction, followed by PTN and OC with insignificance between them.
In regard to the transportations of the canals, Protaper Next have shown highest level of transportation changes at 6mm level only, while at the other levels, there was no statistically difference between the three groups.
As for curvature changes, there was insignificant difference between the groups.
Within the limitation of this study, it can be concluded that:
• WOG, PTN and OC systems were all suitable for preparation of molar root canals with moderate curvature.
• Single file systems better respected the original canal anatomy compared with multi-file system.
• WOG Reciprocating single file system was able to reduce Enterococcus Faecalis CFU.