Related Experiment Video
Updated: Jun 17, 2026

Scanning Electron Microscopic Evaluation of Surface Defects of Remover Retreatment File After Single and Multiple Uses
Published on: October 11, 2024
Cyclic fatigue and fracture characteristics of ground and twisted nickel-titanium rotary files
Hyeon-Cheol Kim1, Jiwan Yum, Bock Hur
1Department of Conservative Dentistry, School of Dentistry, Pusan National University, Busan, Korea.
Introduction:
The purposes of this study were to compare the fatigue resistance of traditional, ground nickel-titanium rotary instruments with the Twisted File and to examine the fracture characteristics of the fatigued fragment.
Methods:
Size #25, 0.06 tapered, TF (SybronEndo), RaCe (FKG Dentaire), Helix (DiaDent), and ProTaper F1 (Dentsply Maillefer) were examined with scanning electron microscope for surface characteristics before subjected to a cyclic (rotational bending) fatigue test. The time until fracture was recorded to calculate the number of revolutions for each instrument. The data were compared for differences by using analysis of variance and post hoc Scheffé test. The fragments were examined with scanning electron microscope both in lateral view and fractographically.
Results:
TF showed a significantly higher resistance to cyclic fatigue than other nickel-titanium files that were manufactured with a grinding process (P < .05). The path of crack propagation appeared to be different for electropolished (TF and RaCe) versus non-electropolished (Helix and ProTaper) instruments.
Conclusions:
Although all specimens showed similar fractographic appearance, which indicated a similar fracture mechanism, instruments with abundant machining grooves seemed to have a higher risk of fatigue.
Related Concept Videos
Fatigue
Residual Stresses in Circular Shafts
Frictional Forces on Screws
A jack with a square-threaded screw is a mechanical device used to lift heavy loads by applying a force at its handle. When the force is applied, the screw turns, raising the load. The screw can...
Stress Concentrations in Circular Shafts
Deformation in a Circular Shaft
Torsion of Noncircular Members

