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不同横截面设计的镍钛器械在模拟弯曲根管预备过程中的力学响应

Mechanical response of nickel-titanium instruments with different cross-sectional designs during shaping of simulated curved canals.

作者信息

Kim H C, Kim H J, Lee C J, Kim B M, Park J K, Versluis A

机构信息

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

出版信息

Int Endod J. 2009 Jul;42(7):593-602. doi: 10.1111/j.1365-2591.2009.01553.x. Epub 2009 May 8.

Abstract

AIM

To evaluate how different cross-sectional designs affect stress distribution in nickel-titanium (NiTi) instruments during bending, torsion and simulated shaping of a curved canal.

METHODOLOGY

Four NiTi rotary instruments with different cross-sectional geometries were selected: ProFile and HeroShaper systems with a common triangle-based cross section, Mtwo with an S-shaped rectangle-based design and NRT with a modified rectangle-based design. The geometries of the selected files were scanned in a micro-CT and three-dimensional finite-element models were created for each system. Stiffness characteristics for each file system were determined in a series of bending and torsional conditions. Canal shaping was simulated by inserting models of the rotating file into a 45 degrees curved canal model. Stress distribution in the instruments was recorded during simulated shaping. After the instruments were retracted from the canal, residual stresses and permanent bending of their tips due to plastic deformation were determined.

RESULTS

The greatest bending and torsional stiffness occurred in the NRT file. During simulated shaping, the instruments with triangle-based cross-sectional geometry had more even stress distributions along their length and had lower stress concentrations than the instruments with rectangle-based cross sections. Higher residual stresses and plastic deformations were found in the Mtwo and NRT with rectangle-based cross-sectional geometries.

CONCLUSIONS

Nickel-titanium instruments with rectangle-based cross-sectional designs created higher stress differentials during simulated canal shaping and may encounter higher residual stress and plastic deformation than instruments with triangle-based cross sections.

摘要

目的

评估不同横截面设计如何影响镍钛(NiTi)器械在弯曲、扭转以及模拟弯曲根管塑形过程中的应力分布。

方法

选择四种具有不同横截面几何形状的镍钛旋转器械:具有常见三角形横截面的ProFile和HeroShaper系统、具有S形矩形设计的Mtwo以及具有改良矩形设计的NRT。在微型计算机断层扫描(micro-CT)中扫描所选器械的几何形状,并为每个系统创建三维有限元模型。在一系列弯曲和扭转条件下确定每个器械系统的刚度特性。通过将旋转器械模型插入45度弯曲的根管模型中来模拟根管塑形。在模拟塑形过程中记录器械中的应力分布。在器械从根管中取出后,确定由于塑性变形导致的尖端残余应力和永久弯曲。

结果

NRT器械的弯曲和扭转刚度最大。在模拟塑形过程中,具有三角形横截面几何形状的器械沿其长度方向的应力分布更均匀,并且比具有矩形横截面的器械具有更低的应力集中。在具有矩形横截面几何形状的Mtwo和NRT中发现了更高的残余应力和塑性变形。

结论

与具有三角形横截面的器械相比,具有矩形横截面设计的镍钛器械在模拟根管塑形过程中产生更高的应力差异,并且可能会遇到更高的残余应力和塑性变形。

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