Department of Conservative Dentistry and Endodontics, SRM Dental College, Chennai, India.
Department of Conservative Dentistry and Endodontics, SRM Dental College, Chennai, India.
J Endod. 2018 Apr;44(4):654-658. doi: 10.1016/j.joen.2017.12.013. Epub 2018 Feb 14.
Single cross-sectional nickel-titanium (NiTi) rotary instruments during continuous rotations are subjected to constant and variable stresses depending on the canal anatomy. This study was intended to create 2 new experimental, theoretic single-file designs with combinations of triple U (TU), triangle (TR), and convex triangle (CT) cross sections and to compare their bending stresses in simulated root canals with a single cross-sectional instrument using finite element analysis.
A 3-dimensional model of the simulated root canal with 45° curvature and NiTi files with 5 cross-sectional designs were created using Pro/ENGINEER Wildfire 4.0 software (PTC Inc, Needham, MA) and ANSYS software (version 17; ANSYS, Inc, Canonsburg, PA) for finite element analysis. The NiTi files of 3 groups had single cross-sectional shapes of CT, TR, and TU designs, and 2 experimental groups had a CT, TR, and TU (CTU) design and a TU, TR, and CT (UTC) design. The file was rotated in simulated root canals to analyze the bending stress, and the von Mises stress value for every file was recorded in MPa. Statistical analysis was performed using the Kruskal-Wallis test and the Bonferroni-adjusted Mann-Whitney test for multiple pair-wise comparison with a P value <.05 (95 %).
The maximum bending stress of the rotary file was observed in the apical third of the CT design, whereas comparatively less stress was recorded in the CTU design. The TU and TR designs showed a similar stress pattern at the curvature, whereas the UTC design showed greater stress in the apical and middle thirds of the file in curved canals. All the file designs showed a statistically significant difference.
The CTU designed instruments showed the least bending stress on a 45° angulated simulated root canal when compared with all the other tested designs.
在连续旋转过程中，单次横截面镍钛（NiTi）旋转器械会根据根管解剖结构承受恒定和变化的应力。本研究旨在创建 2 种新的实验性、理论性的单文件设计，结合三 U（TU）、三角（TR）和凸三角（CT）横截面，并使用有限元分析比较与单一横截面器械在模拟根管中的弯曲应力。
使用 Pro/ENGINEER Wildfire 4.0 软件（PTC Inc，马萨诸塞州 Needham）和 ANSYS 软件（版本 17；ANSYS，Inc，宾夕法尼亚州 Canonsburg）创建具有 45°曲率的模拟根管的三维模型和 5 种横截面设计的 NiTi 文件，用于有限元分析。3 组 NiTi 文件具有 CT、TR 和 TU 设计的单一横截面形状，2 个实验组具有 CT、TR 和 TU（CTU）设计和 TU、TR 和 CT（UTC）设计。在模拟根管中旋转文件以分析弯曲应力，并以 MPa 记录每个文件的 von Mises 应力值。使用 Kruskal-Wallis 检验和 Bonferroni 调整的 Mann-Whitney 检验进行统计分析，用于多个两两比较的 P 值<.05（95%）。
在 CT 设计中，旋转锉的最大弯曲应力出现在根尖的三分之一处，而在 CTU 设计中记录到的应力相对较小。TU 和 TR 设计在曲率处显示出相似的应力模式，而 UTC 设计在弯曲根管的根尖和中间三分之一处显示出更大的应力。所有文件设计均显示出统计学上的显著差异。
与所有其他测试设计相比，CTU 设计的器械在 45°角模拟根管中显示出最小的弯曲应力。
