الفهرس 
Title : Assessment of Shaping Ability of HyFlex EDM in Comparison to Reciproc Files Using Cone-Beam Computed Tomography (CBCT) (An In Vitro Study)
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Abstract
Aim: The aim of the current study was to evaluate the canal transportation and centering ability of HyFlex EDM in comparison to Reciproc using CBCT. Materials and methods: Twenty-six curved mesiobuccal canals of human extracted mandibular molars with a range of curvature from (25o- 40o) were selected and assigned into two equal groups. Access cavities were prepared, distal halves of the teeth were discarded and the mesial halves were used for the study. The occlusal surface of the samples was reduced so that the sample length was fixed to 17 mm and working length was adjusted to be 16mm. The samples were scanned by CBCT after being mounted on customized acrylic base and then rescanned after the instrumentation using the exact scanning protocol. Root canals of each group were prepared following the manufacturers’ instructions using OneFile and R25 instruments for Hyflex EDM and Reciproc groups respectively.The software OnDemand 3D App was employed to superimpose pre- and post-instrumentation scans using the fusion module. Axial slices were taken from both scans at 3 mm, 5 mm and 8 mm from the root apex. The change in dentin thickness was measured from both scans simultaneously. Canal transportation values and directions as well as the centering ability of the instruments were evaluated based on two formulae developed by Gambill et al. Data was statistically analyzed using the following tests; Friedman{u2019}s test for comparisons within each group, Wilcoxon signed rank test for pairwise comparison between significant variables and Mann-Whitney test for comparisons between the two groups. A P-value less than or equal to 0.05 was considered statistically significant