Deflecting load of nickel titanium rotary instruments during cyclic fatigue

Ahmed Jamleh, Chihiro Kobayashi, Yoshio Yahata, Arata Ebihara, Hideaki Suda

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


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 (DLm) was calculated. The averages of NCF and DLm 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.

Original languageEnglish
Pages (from-to)389-393
Number of pages5
JournalDental Materials Journal
Issue number3
Publication statusPublished - 2012


  • Deflecting load
  • NiTi rotary file
  • Number of cycles to fracture


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