الفهرس 
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Abstract
Summary :
The aim of the study was to compare the CF resistance of Hyflex EDM, M3 Pro gold and Soco Pro files at room temperature and body temperature and to document the corresponding phase transformations.
Total of 60 files #25 of these brands were selected for the study, CF testing was done using a dynamic CF testing device along with a custom made artificial stainless steel canals which had 90° and 5mm radius of curvature. There was three groups, each (n=20). Each group was subdivided into 2 subgroups according to the environment temperature: Subgroup a (room temperature) and Subgroup b (body temperature), samples were rotated continuously until fracture in the artificial canals, the NCF was calculated. Phase transformation temperatures for 2 instruments of each brand were analyzed by DSC.
Results showed that Hyflex EDM files had the highest CF resistance followed by M3 Pro gold files then Soco Pro files at room and body temperature. There were no significant difference between CF resistance of Hyflex EDM and M3 Pro gold at room and body temperatures, but
CF resistance was significantly decreased for Soco Pro at
body temperature.
DSC showed that Hyflex EDM and M3 Pro gold were in the same state (martensitic state) at room and body temperatures, but Soco Pro was in mixed state (martensitic and austenitic) at room temperature and in austenitic state at body temperature.
Conclusions:
Under the circumstances of this study, it could be concluded that:
• The custom made device used in this study showed efficiency in dynamic CF testing at different temperatures.
• Different heat treatments had significant effect on CF resistance.
• The effect of temperature on CF resistance was not identical for all NiTi files. There was significant difference between CF resistance at room and body temperatures only for files which have transformation temperature in between these temperatures.
Recommendations:
• Further investigations are needed to evaluate the mechanical properties and metallurgical characteristics of the new heat treated NiTi files.
• Further investigations on the interaction between temperature and CF resistance.