Related Experiment Video
Updated: May 21, 2026

Scanning Electron Microscopic Evaluation of Surface Defects of Remover Retreatment File After Single and Multiple Uses
Published on: October 11, 2024
Deflecting load of nickel titanium rotary instruments during cyclic fatigue
Ahmed Jamleh1, Chihiro Kobayashi, Yoshio Yahata
1Pulp Biology and Endodontics, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
Abstract:
The dispersion of the lifetime of NiTi instruments, and their deflecting load (DL) changes during cyclic fatigue were investigated. A total of 120 ProFile NiTi rotary instruments were tested using a specially designed cyclic fatigue testing apparatus with three pins. Using these pins, the instrument was bent and rotated at 300 rpm to fracture. DL was recorded using a load cell attached to the central pin. For each sample, the working time was converted to number of cycles to fracture (NCF) and the mean DL (DL(m)) was calculated. The averages of NCF and DL(m) of 120 samples were 584.3±180.5 cycles and 6.44±0.91 N, respectively. All samples showed a sequential decrease in DL during rotation. Based on the present study, it is impossible to estimate the lifetime of a NiTi instrument from NCF. Thus, the change in DL could be an alternative criterion to determine the remaining lifetime.
More Related Videos
Related Concept Videos
Fatigue
Residual Stresses in Circular Shafts
Stress Concentrations in Circular Shafts
Residual Stresses
Yield Criteria for Ductile Materials under Plane Stress
The Maximum Shearing Stress Criterion, also known as the...
Unsymmetric Loading of Thin-Walled Members
The concept of the shear center is crucial in countering the...

