Cell Biochemistry and Biophysics

, Volume 70, Issue 2, pp 1091–1095 | Cite as

Analysis of Mtwo Rotary Instrument Separation During Endodontic Therapy: A Retrospective Clinical Study

  • Nan-Nan Wang
  • Jiu-Yu Ge
  • Si-Jing Xie
  • Ge Chen
  • Min Zhu
Original Paper


To analyze the incidence of instrument separation (IS) and the factors influencing it, when associated with Mtwo rotary system (VDW, Munich, Germany) during endodontic therapy. A retrospective study involving a total of 24,108 root canals (11,036 endodontic treated teeth) was conducted at Nanjing Stomatology Hospital between January 2011 and March 2013. The information included were tooth type, root canal curvature, number of fractured instruments, length of the separated fragments, and the distance from broken tip to apex. The incidence of IS was observed to be 2.2 % according to the number of teeth and 1.0 % according to the number of root canals. Many of the separated fragments were 2–4 mm in length and the mean length was 3.07 ± 1.46 mm, and 78.4 % of fractures occurred in the apex. The mean length of separated fragments in severely curved canals was maximum, while ultra-severe curved canals was observed to be minimum. Mtwo instruments demonstrated an extremely low fracture rate during endodontic therapy. Molar teeth (especially lower molars) and the degree of canal curvature had a significant effect on the incidence of IS.


Instrument fracture Mtwo instruments Torsional stress 



This study was supported by Constructional Project of National Key Clinical Specialty, China.

Conflict of Interest

The authors deny any conflict of interests.


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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Nan-Nan Wang
    • 1
  • Jiu-Yu Ge
    • 1
  • Si-Jing Xie
    • 1
  • Ge Chen
    • 1
  • Min Zhu
    • 1
  1. 1.Department of Cariology and Endodontics, Institute and Hospital of StomatologyNanjing University Medical SchoolNanjingChina

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