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Effect of autoclave sterilization on cyclic fatigue and torsional fracture resistance of NiTi rotary instruments

  • Wooyoung Kim
  • Soram Oh
  • Gil-Joo Ryu
  • Tae-Hwan Kim
  • Sung-Jae Kim
  • Dong-Hyung Kim
  • Bin-Na Lee
  • Kee-Yeon Kum
  • Seok Woo Chang
  • Ji-Hyun JangEmail author
Original Article


The purpose of this study is to assess the effect of autoclave sterilization on the cyclic fatigue and torsional fracture resistance of ProTaper Universal (PTU), K3XF, HyFlex EDM (EDM), and TF adaptive (TFA). Sixty instruments from each file type were divided into two categories for cyclic fatigue group (CGr) and torsional fracture group (TGr). CGr and TGr were divided into three subgroups, respectively, consisting of ten instruments from each file type. Cyclic fatigue fracture test was performed using artificial canal made of stainless steel, and the mean number of cycles to failure (NCF) were determined. CGr1, the files were tested to establish baseline for NCF; CGr2, the files were tested cyclic fatigue after 10 cycles of autoclave; CGr3, instruments were autoclaved after being cycled to 25, 50, and 75% of corresponding NCF determined in CGr1, followed by cyclic fatigue test. The torsional fracture test was performed without autoclave (TGr1), after 3-cycle autoclave (TGr2), and 7-cycle autoclave (TGr3), respectively, which evaluated maximum torque and angular deflection. NCF, maximum torque and angular deflection were compared using one-way ANOVA with Bonferroni test. Two-way ANOVA was performed to determine the interaction between ‘autoclave treatment’ and ‘type of NiTi file’. EDM showed highest NCF within the same autoclave treatment. TFA presented the lowest maximum torque and the highest angular deflection, and PTU presented the lowest angular deflection. Within the same NiTi file systems, most of NCF, maximum torque and angular deflection of tested files were not significantly influenced by autoclave condition.


Autoclave sterilization Cyclic fatigue fracture NiTi file Torsional fracture Heat treatment 



This research was supported by the Bio & Medical Technology Development Program of the National Research Foundation (NRF) & funded by the Korean government (MSIP&MOHW) (No. 2017M3A9E4048170).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Statement of clinical relevance

Multiple autoclave sterilization generally did not adversely affect the cyclic and torsional fracture resistance of ProTaper Universal, K3XF, TF Adaptive, and HyFlex EDM.


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Copyright information

© The Society of The Nippon Dental University 2019

Authors and Affiliations

  1. 1.Department of Conservative Dentistry, Graduate SchoolKyung Hee UniversitySeoulRepublic of Korea
  2. 2.Department of Conservative Dentistry, School of DentistryKyung Hee UniversitySeoulRepublic of Korea
  3. 3.GoodWill Dental HospitalBusanRepublic of Korea
  4. 4.Department of Conservative Dentistry, School of DentistryDental Science Research Institute, Chonnam National UniversityGwang-juRepublic of Korea
  5. 5.Seoul National University Dental Hospital for Persons with Special Needs, National Dental Care Center for Persons with Special Cares, Department of Conservative DentistryDental Research Institute, Seoul National University Dental Hospital, Seoul National University School of DentistrySeoulRepublic of Korea

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