, Volume 107, Issue 3, pp 324–332 | Cite as

Cyclic fatigue resistance of three rotary file systems in a dynamic model after immersion in sodium hypochlorite

  • Paulo Jorge PalmaEmail author
  • Ana Messias
  • António Rosa Cerqueira
  • Luís Diogo Tavares
  • Francisco Caramelo
  • Luís Roseiro
  • João Miguel Santos
Original Article


To evaluate the effect of immersion in 3% sodium hypochlorite solution in the resistance to cyclic fatigue of three nickel–titanium (NiTi) rotary file systems, ProTaper Next (PTN), Hyflex CM (CM), and Hyflex EDM (EDM), in a mechanical model featuring axial movement. Ninety instruments of three different NiTi rotary file systems, PTN (size 25, 0.06 taper), CM (25, 0.06), and EDM (25/~, variable taper), were randomly divided according to a 3 × 3 factorial design and tested under dynamic immersion in a 3% NaOCl solution (1 or 5 min) or without immersion, making a total of 9 groups (n = 10). Files were tested in an artificial root canal with 45° angle and 5 mm radius apical curvature being submitted to back-and-forth movements until fracture. Statistical analysis was performed using two-way factorial ANOVA with Bonferroni post-hoc tests, at a significance level of 5%. Instruments were evaluated for reliability using a Weilbull approach. Regardless of the immersion treatment, PTN had on average 1200 ± 178 cycles to fracture, CM had 1949 ± 362, and EDM had 5573 ± 853, which was a significantly different (P < 0.01). The NaOCl immersion promoted a significant reduction in the mean number of cycles to fracture (P = 0.01), and was reflected in a significant reduction of the characteristic life of the instruments of the CM end EDM groups. Within this study conditions, EDM instruments performed better to cyclic fatigue followed by CM and then PTN. Immersion in NaOCl decreased the resistance to cyclic fatigue of all tested instruments, but affected more those manufactured from CM wire.


Dynamic cyclic fadigue test Sodium hypochorite M-wire Controlled memory Hyflex CM Electrical discharge machining hyflex EDM 



The authors thanks Coltène and DentsplySirona for providing the instruments.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© The Society of The Nippon Dental University 2018

Authors and Affiliations

  1. 1.Institute of Endodontics, Faculty of MedicineUniversity of CoimbraCoimbraPortugal
  2. 2.Department of Dentistry, Faculty of MedicineUniversity of CoimbraCoimbraPortugal
  3. 3.Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of MedicineUniversity of CoimbraCoimbraPortugal
  4. 4.Laboratory of Biostatistics and Medical Informatics (LBIM), Faculty of MedicineUniversity of CoimbraCoimbraPortugal
  5. 5.Department of Mechanical Engineering, Institute of Engineering of CoimbraPolytechnic - ISECCoimbraPortugal
  6. 6.Institute for Interdisciplinary Research (IIIUC)University of CoimbraCoimbraPortugal

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