Stress distribution for NiTi files of triangular based and rectangular based cross-sections using 3-dimensional finite element analysis

Article information

Restor Dent Endod. 2009;34(1):1-7

Publication date (electronic) : 2009 January 31

doi : https://doi.org/10.5395/JKACD.2009.34.1.001

Hyun-Ju Kim ¹, Chan-Joo Lee ², Byung-Min Kim ², Jeong-Kil Park ¹, Bock Hur ¹, Hyeon-Cheol Kim ¹

¹Department of Conservative Dentistry, School of Dentistry, Pusan National University, Busan, Korea.

²Division of Precision Manufacturing Systems, Pusan National University, Busan, Korea.

Corresponding Author: Hyeon-Cheol Kim. Department of Conservative Dentistry, School of Dentistry, Pusan National University, 1-10 Ami-Dong, Seo-Gu, Busan, Korea. Tel: 82-51-240-7978, golddent@pusan.ac.kr

Received 2008 June 13; Revised 2008 July 03; Accepted 2008 July 08.

Abstract

The purpose of this study was to compare the stress distributions of NiTi rotary instruments based on their cross-sectional geometries of triangular shape-based cross-sectional design, S-shaped cross-sectional design and modified rectangular shape-based one using 3D FE models.

NiTi rotary files of S-shaped and modified rectangular design of cross-section such as Mtwo or NRT showed larger stress change while file rotation during simulated shaping.

The stress of files with rectangular cross-section design such as Mtwo, NRT was distributed as an intermittent pattern along the long axis of file. On the other hand, the stress of files with triangular cross-section design was distributed continuously.

When the residual stresses which could increase the risk of file fatigue fracture were analyzed after their withdrawal, the NRT and Mtwo model also presented higher residual stresses.

From this result, it can be inferred that S-shaped and modified rectangular shape-based files were more susceptible to file fracture than the files having triangular shape-based one.

Keywords: Nickel-titanium file; Stress distribution; Triangular; Rectangular; Cross-sectional geometry; Finite element

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This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Figure 1

Cross-sectional and longitudinal geometries of four NiTi files; (A) ProFile .06 / #30, (B) HeroShaper .06 / #30, (C) Mtwo .05 / #30, (D) NRT .06 / #30.

Figure 2

Final FE models of four NiTi files and simulated root canal; (A) ProFile .06 / #30, (B) HeroShaper .06 / #30, (C) Mtwo .05 / #30, (D) NRT .06 / #30.

Figure 3

External surface and internal sectional view of stress distribution during simulated root canal shaping; (A) ProFile .06 / #30, (B) HeroShaper .06 / #30, (C) Mtwo .05 / #30, (D) NRT .06 / #30.

Figure 4

The stress changing cycles of the nodes (red point) where maximal von Mises stresses were concentrated.

Figure 5

The residual stress distribution after elastic recovery of withdrawn file (A; ProFile 326 MPa, B; HeroShaper 352 MPa, C; Mtwo 448 MPa, D; NRT 571 MPa).