Endodontic instruments after torsional failure: Nanoindentation test

Authors

  • Ahmed Jamleh,

    1. Department of Endodontics, College of Dentistry, King Saud bin Abdulaziz University for Health Sciences, National Guard Health Affairs, Riyadh, Saudi Arabia
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  • Alireza Sadr,

    1. Global Center of Excellence (GCOE), International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Tokyo, Japan
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  • Naoyuki Nomura,

    1. Department of Materials Processing, Graduate School of Engineering, Tohoku University, Tohoku, Japan
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  • Arata Ebihara,

    Corresponding author
    1. Department of Pulp Biology and Endodontics, Division of Oral Health Sciences, Medical and Dental Sciences Track, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
    • Address for reprints: Arata Ebihara, Department of Pulp Biology and Endodontics, Division of Oral Health Sciences, Medical and Dental Sciences Track, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan

      E-mail: a.ebihara.endo@tmd.ac.jp

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  • Yoshio Yahata,

    1. Faculty of Dentistry, Department of Endodontics, Showa University, Tokyo, Japan
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  • Takao Hanawa,

    1. Department of Metallic Biomaterials, Division of Biomedical Materials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
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  • Junji Tagami,

    1. Global Center of Excellence (GCOE), International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Tokyo, Japan
    2. Department Cariology and Operative Dentistry, Division of Oral Health Sciences, Medical and Dental Sciences Track, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
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  • Hideaki Suda

    1. Global Center of Excellence (GCOE), International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Tokyo, Japan
    2. Department of Pulp Biology and Endodontics, Division of Oral Health Sciences, Medical and Dental Sciences Track, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
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  • Conflicts of interest: None.

Summary

This study aimed to evaluate effects of torsional loading on the mechanical properties of endodontic instruments using the nanoindentation technique. ProFile (PF; size 30, taper 04; Dentsply Maillefer, Switzerland) and stainless steel (SS; size 30, taper 02; Mani, Japan) instruments were subjected to torsional test. Nanoindentation was then performed adjacent to the edge of fracture (edge) and at the cutting part beside the shank (shank). Hardness and elastic modulus were measured under 100-mN force on 100 locations at each region, and compared to those obtained from the same regions on new instruments. It showed that PF and SS instruments failed at 559 ± 67 and 596 ± 73 rotation degrees and mean maximum torque of 0.90 ± 0.07 and 0.99 ± 0.05 N-cm, respectively. Hardness and elastic modulus ranged 4.8–6.7 and 118–339 GPa in SS, and 2.7–3.2 and 52–81 GPa in PF. Significant differences between torsion-fractured and new instruments in hardness and elastic modulus were detected in the SS system used. While in PF system, the edge region after torsional fracture had significantly lower hardness and elastic modulus compared to new instruments. The local hardness and modulus of elasticity of endodontic instruments adjacent to the fracture edge are significantly reduced by torsional loading. SCANNING 36:437–443, 2014. © 2014 Wiley Periodicals, Inc.

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