الفهرس 
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Abstract
The aim of the study was to evaluate surface defects and crystalline structural changes in reciproc and reciproc blue rotary nickel-titanium files after use.
Sixty lower first molars were collected, Proximal radiographic views were taken to mesiobuccal and mesiolingual canals exhibiting a curvature, average between (25o - 35o). The method was done according to Schneider method by using Image J software.
The each tooth the mesiobuccal canal is done by reciproc file but the mesiolingual by reciproc blue file. EDTA used during the mechanical preparation. After each file the canal was irrigated by 5.25% NAOCL.
A total number of 22 files were used, 20 experimental files and 2 controlled files (one from each system for X-Ray diffraction assessment). Then each group was subdivided into 2 subgroups.
group I: 60 MB canals were prepared using 10 Reciproc files.
group II: 60 ML canals were prepared using 10 Reciproc blue files.
Classification of each group into two subgroups A & B:
Subgroup A: 10 files were used for 30 samples.
Subgroup B: the same files were used to prepare other 3 canals.
1) Scanning Electron Microscopy (SEM)
For evaluating the topography of the files, the presence or absence of the defects was checked on the surface of every file. Field Emission Scanning Electron Microscope was used with magnification from 300x to 1000x.
Results showed that there was no statistically significant difference between Reciproc and Reciproc Blue systems in new, three and six canals preparation. BUT There was a significant difference between new and after three and six canals used in disruption of cutting edge, debris and scraping.
2) X-Ray Diffraction (XRD)
Segments from the shank portions of Ni-Ti files was cut into approximately 4- 8 mm. They were adhered together and ground to obtain a plane. Then peaks was identified.
The results showed that the XRD analyses confirmed the presence of R phase in new files which decreased after use. And presence martensitc and R phase in Reciproc blue and increase R phase after use.