Int J Stomatol

Int J Stomatol ›› 2026, Vol. 53 ›› Issue (5): 696-702.doi: 10.7518/gjkq.2026134

• Original Article • Previous Articles    

Application of finite element simulation in preventing torsional fracture of nickel-titanium root canal files

Ruijie Liu(),Yan Sheng,Hao Zhou,Yaqun Kong()   

  1. Dept. of Stomatology, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
  • Received:2026-01-04 Revised:2026-05-13 Online:2026-09-01 Published:2026-08-28
  • Contact: Yaqun Kong E-mail:liuruijie2010@163.com;kyq31@163.com

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Abstract:

Objective This study aimed to predict the maximum allowable torsional moment and rotation angle of nickel-titanium root canal files after jamming during root canal preparation to prevent torsional fracture. Methods 　Finite element simulation was used to calculate the stress distribution of the file and the torsional moment at the file handle when the file continued to rotate after jamming. The effects of factors, such as file and root canal morphology, on stress and torque were investigated. Results 　After the Von Mises stress reached the material phase transformation point (400‒600 MPa) during the continued rotation of the jammed file, the “torque‒rotation angle” curve entered a plateau region. When the local stress at the cross-section reached the material fracture strength (>1 000 MPa), the torque did not change significantly with the rotation angle (i.e., remained in the plateau region) due to the non-uniform stress distribution (coefficient of variation: 0.65). Depending on the file and root canal combination, the torque at fracture ranged from 0.5 N·mm to 3 N·mm, and the rotation angle ranged from 200° to 400°. Conclusion 　Finite element simulation can establish a numerical relationship between the fracture stress of the file and the allowable torsional moment and rotation angle in the file‒canal system during root canal preparation jamming, thereby providing warning parameters to effectively prevent fracture incidents.

Key words: nickel-titanium root canal file, root canal preparation, finite element simulation, fracture stress, torsional moment, rotation angle

CLC Number: 

  • R783.1

TrendMD: 

Fig 1

Geometry of the endodontic files and root canals"

Tab 1

Parameters of the constitutive model for NiTi alloy"

参数特性数值
EA奥氏体弹性模量42.53 GPa
νA泊松比0.33
EM马氏体弹性模量12.828 GPa
εL相变应变率10%
σLS加载过程相变开始应力492 MPa
σLE加载过程相变结束应力630 MPa
σMS卸载过程相变开始应力192 MPa
σME卸载过程相变结束应力97 MPa
T参考温度22 ℃
ρ密度6 300 kg/m3

Fig 2

Stress-strain curve of NiTi shape memory alloy"

Fig 3

Boundary conditions and loading method"

Tab 2

Cross-sectional shapes of endodontic files and root canal variations as the variables"

根管二刃锉刀1三刃锉刀2四刃锉刀3大圆截面4小圆截面5
根管11-11-21-31-41-5
根管22-12-22-32-42-5

Tab 3

Relative orientation angle of endodontic file cross-section to root canal as the variables"

根管锉根管1旋转角度
α0α1α2α3α4α5α6α7α8α9
三刃锉刀22-α02-α12-α22-α32-α42-α52-α62-α72-α82-α9

Tab 4

Pitch of endodontic file as the variable"

根管锉+根管组合螺距参数
d0d1d2d3d4d5
三刃锉刀2+根管12-d02-d12-d22-d32-d42-d5

Fig 4

Von Mises stress and torque of the endodontic file after binding in the root canal during rotary preparation"

Fig 5

Von Mises stress distribution contours of the endodontic file when the torque at the tip reaches the plateau inflection point and the Von Mises stress reaches 1 000 MPa"

Fig 6

Influence of endodontic file cross-sectional geometry, relative orientation angle, and pitch on its Von Mises stress and apical tip torque"

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