Deflecting load of nickel titanium rotary instruments during cyclic fatigue.
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.
Pulp Biology and Endodontics, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
Ahmed
A
Jamleh
Chihiro
C
Kobayashi
Yoshio
Y
Yahata
Arata
A
Ebihara
Hideaki
H
Suda
D003722:Dental Alloys; D003754:Dental High-Speed Equipment; D003799:Dental Stress Analysis; D004868:Equipment Failure; D009532:Nickel; D013314:Stress, Mechanical; D013997:Time Factors; D014025:Titanium
D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium