الفهرس 
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Abstract
Aim of the Study
To measure the apical root transportation and changes in canal curvature of XP Endo shaper and compare it with TRUE Shape and Hyflex CM Ni-Ti rotary system.
Selection of the samples
A total of sixty human permanent mandibular first molars extracted due to periodontal or orthodontic reasons were collected from the Department of Oral Surgery, Faculty of Dentistry, Minia University. Preoperative periapical radiographs were taken to inspect the mesial roots and to determine the angle of root curvature according to Schneider’s method (71) .
Inclusion criteria:
Complete root formation (mature apex), in order to allow instrumentation in tapered canals with well-developed apical constriction.
Teeth have no root caries.
Teeth have no internal or external root resorption.
Teeth have no previous endodontic treatment.
Teeth have no signs of cracks, In order to avoid vertical fracture or horizontal fracture during instrumentation of the root canals and loss of the sample.
Mesio-buccal root curvatures ranging between 25° – 35° according to the Schneider’s method will be selected.(71)
Exclusion criteria:
Teeth with initial binding file more than 20#
Teeth with multiple curvatures.
Teeth with rapid apical curvature.
Teeth with calcified canals.
Teeth with anatomic abnormalities such as fusion.
Conclusion:
Under condition of the present study, it can be conclude that:
•The three rotary systems preserved the original canal anatomy
•Under favor of the alloy that HEDM files are made of, they are capable of better adapting to the original shape of the canal.
•CBCT is avaluable research tool for a non-destructive evaluation of shaping procedures in endodontics.
Recommendations
•Further studies are needed to assess the ability of the tested single files to follow the original canal anatomy in different degrees of canal curvature.
•It’s advisable to use Micro-Computed Tomography in assessment of shaping ability of rotary files which may give more accurate results.
•Post manufacturing surface treatment of the files increases its ability to shape the root canal with the minimum degree of transportation.