الفهرس 
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Abstract
The study was done to asses the CFR of Pepsi Gold files and M3 Pro Gold files at BT at 2 different canal radii (3,5mm).
A total of 80 files were tested in a stainless steel artificial canal with 60˚ curvature angle and 2 different radii. Each type was divided into 2 equal groups. Twenty files of each system were tested at 3mm canal radius and the other twenty files were tested at 5mm canal radius. The CFR test was done in BT.The files were tested for the dynamic CF in a special device. The TtF and NCF was recorded.
Three files from each type (new file, file tested in radius 3 and file tested in radius 5) were chosen randomly and scanned by the DSC to evaluate the phase transformation temperature. The specimen was 4-5 mm of the apical part of the file. The DSC analysis were conducted over temperature range from 30°-600°C at a heating rate 5°C ̸ min under nitrogen atmosphere.
The results showed that the Pepsi Gold files had higher CFR than the M3 Pro Gold files. There is significant effect of the canal radius on the CFR. The smaller the curvature radius, the larger the stresses on the file and the lower the CFR of the file. The DSC showed the presence of martensite phase in both Pepsi Gold files and M3 Pro Gold files at BT. However, the austenite phase was appeared for the M3 Pro Gold files at BT in the file tested in 5 mm radius.
Within the limitation of this study, it was concluded that:
1 – Pepsi Gold files have higher fatigue resistance than M3 Pro Gold files
2 – the greater the radius, the higher the cyclic fatigue resistance.
3 – The presence of R phase is associated with higher fatigue resistance.