Ha Jung-Hong, Kwak Sang Won, Versluis Antheunis, Lee Chan-Joo, Park Se-Hee, Kim Hyeon-Cheol
Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, South Korea.
Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, South Korea.
J Dent Sci. 2017 Jun;12(2):173-178. doi: 10.1016/j.jds.2016.11.005. Epub 2017 Mar 14.
BACKGROUND/PURPOSE: Geometric design dictates the mechanical performance of nickel-titanium rotary instruments. Using finite element (FE) analysis, this study evaluated the effects of an off-centered cross-sectional design on the stiffness and stress distribution of nickel-titanium rotary instruments.
We constructed three-dimensional FE models, using ProTaper-NEXT type design (PTN) as well as three other virtual instruments with varied cross-sectional aspect ratios but all with the same cross-sectional area. The cross-sectional aspect ratio of the PTN was 0.75, while others were assigned to have ratios of 1.0 (square), 1.5 (rectangle), and 2.215 (centered-rectangle). The PTN center of the cross-section was '', while others were designed to have 0.9992, 0.7, and 0 for the square, rectangle, and centered-rectangle models, respectively. To compare the stiffness of the four FE models, we numerically analyzed their mechanical response under bending and torque.
Under the bending condition, the square model was found to be the stiffest, followed by the PTN, rectangle, and then the centered-rectangle model. Under the torsion, the square model had the smallest distortion angle, while the rectangular model had the highest distortion angle.
Under the limitation of this study, the PTN type off-centered cross-sectional design appeared the most optimal configuration among the tested designs for high bending stiffness with cutting efficiency while rotational stiffness remained similar with the other designs.
背景/目的：几何设计决定了镍钛旋转器械的机械性能。本研究采用有限元（FE）分析，评估了偏心横截面设计对镍钛旋转器械刚度和应力分布的影响。
我们构建了三维有限元模型，采用ProTaper-NEXT型设计（PTN）以及其他三种虚拟器械，它们具有不同的横截面长宽比，但横截面面积均相同。PTN的横截面长宽比为0.75，其他分别设定为1.0（正方形）、1.5（长方形）和2.215（中心矩形）。PTN的横截面中心为“”，而正方形、长方形和中心矩形模型的其他设计分别为0.9992、0.7和0。为比较四个有限元模型的刚度，我们对它们在弯曲和扭矩作用下的力学响应进行了数值分析。
在弯曲条件下，发现正方形模型刚度最大，其次是PTN、长方形，然后是中心矩形模型。在扭转时，正方形模型的变形角度最小，而矩形模型的变形角度最大。
在本研究的限制范围内，PTN型偏心横截面设计在测试设计中似乎是具有高弯曲刚度和切割效率的最优化配置，而旋转刚度与其他设计相似。
