Journal of Endodontics
Volume 36, Issue 1 , Pages 147-152, January 2010

Cyclic Fatigue and Fracture Characteristics of Ground and Twisted Nickel-Titanium Rotary Files

  • Hyeon-Cheol Kim, DDS, MS, PhD

      Affiliations

    • Department of Conservative Dentistry, School of Dentistry, Pusan National University, Busan, Korea
    • ,
  • Jiwan Yum, DDS, MS

      Affiliations

    • Department of Conservative Dentistry, School of Dentistry, Pusan National University, Busan, Korea
    • ,
  • Bock Hur, DDS, MS, PhD

      Affiliations

    • Department of Conservative Dentistry, School of Dentistry, Pusan National University, Busan, Korea
    • ,
  • Gary Shun-Pan Cheung, MDS, MSc, PhD

      Affiliations

    • Area of Endodontics, Faculty of Dentistry, University of Hong Kong, Hong Kong SAR, China
    • Corresponding Author InformationAddress requests for reprints to Gary Shun-Pan Cheung, MDS, MSc, PhD, Area of Endodontics, Faculty of Dentistry, 3/F, Prince Philip Dental Hospital, 34 Hospital Road, Saiyingpun, Hong Kong.

Abstract 

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.

Key Words: Cyclic fatigue, electropolishing, fracture, machining grooves, nickel-titanium, rotary instrument, surface defect, Twisted File

 

PII: S0099-2399(09)00824-3

doi:10.1016/j.joen.2009.09.037

Journal of Endodontics
Volume 36, Issue 1 , Pages 147-152, January 2010