Iosif Laura, Dimitriu Bogdan, Niţoi Dan Florin, Amza Oana
Faculty of Dentistry, University of Medicine and Pharmacy "Carol Davila" Bucharest, 17-21 Calea Plevnei Street, Sector 1, 010221 Bucharest, Romania.
Faculty of Industrial Engineering and Robotics, University POLITEHNICA of Bucharest, 313 Splaiul Independenței Street, 060042 Bucharest, Romania.
Healthcare (Basel). 2023 Nov 7;11(22):2918. doi: 10.3390/healthcare11222918.
Endodontic shaping causes stress and strain in the root canal dentin. Dentin microcracks have the potential to be later followed by root fractures occurring under the occlusal load. The aim of our research was to theoretically determine the values of such dentinal states of stress and strain during the endodontic shaping of curved root canals using finite element analysis (FEA).
To highlight the stress concentrations in dentin, two geometric models were created considering the volume of the curved dental root and the contact between the endodontic file and the root canal walls. The application of forces with different values was simulated both on a uniform curved root canal and on a root canal with an apical third curvature of 25° as they would be applied during the preparation of a root canal.
In the case of the first model, which was acted upon with a force of 5 N, the deformations of the root canal appeared along the entire working length, reaching the highest values in the apical third of the root, although there were no geometric changes in the shape of the root canal. Regarding the second root model, with an apical third curvature of 25°, although the applied force was 2 N, the deformations were accompanied by geometric changes in the shape of the root, especially in the upper part of the apical third. At a higher force of 7 N exerted on the endodontic file, the geometric shape changed, and the deformation reached extreme critical values. The resulting tensile stresses appearing in the experimental structure varied similarly to the deformations.
Significant stress and strain can develop, especially in the apical third of curved root canals during their shaping, and the risk of cracks is higher for endodontically treated teeth presenting severe curvatures in the apical third of the root.
根管预备会导致根管牙本质产生应力和应变。牙本质微裂纹有可能随后在咬合负荷下引发牙根骨折。我们研究的目的是使用有限元分析（FEA）从理论上确定弯曲根管根管预备过程中此类牙本质应力和应变状态的值。
为突出牙本质中的应力集中，创建了两个几何模型，考虑了弯曲牙根的体积以及根管锉与根管壁之间的接触。在均匀弯曲根管和根尖三分之一处曲率为25°的根管上模拟施加不同值的力，如同根管预备过程中施加的力一样。
在第一个模型中，施加5 N的力时，根管变形沿整个工作长度出现，在牙根根尖三分之一处达到最大值，尽管根管形状没有几何变化。对于第二个牙根模型，根尖三分之一处曲率为25°，尽管施加的力为2 N，但变形伴随着牙根形状的几何变化，尤其是在根尖三分之一的上部。当对根管锉施加7 N的更大力量时，几何形状发生变化，变形达到极端临界值。实验结构中产生的拉应力变化与变形类似。
在弯曲根管预备过程中，尤其是在根尖三分之一处，会产生显著的应力和应变，对于根尖三分之一处呈现严重弯曲的根管治疗牙齿，出现裂纹的风险更高。
