Shanghai Key Laboratory of Stomatology, Department of Endodontics, Ninth People's Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, China.
Department of Endodontics, University of Illinois at Chicago, Chicago, IL, USA.
Int Endod J. 2018 Feb;51(2):233-239. doi: 10.1111/iej.12825. Epub 2017 Aug 21.
To investigate and compare the effects of two apical canal instrumentation protocols on apical stress distribution at the root apex under vertical compaction of gutta-percha and occlusal loads using finite element analysis.
Three finite element analysis models of a mandibular first premolar were reconstructed: an original canal model, a size 35, .04 taper apical canal enlargement model and a Lightspeed size 60 apical canal enlargement model. A 15 N compaction force was applied vertically to the gutta-percha 5 mm from the apex. A 175 N occlusal load in two directions (vertical and 45° to the longitudinal axis of the tooth) was simulated. Stresses in the apical 2 mm of the root were calculated and compared among the three models.
Under vertical compaction, stresses in the apical canal instrumented by Lightspeed size 60 (maximal 3.3 MPa) were higher than that of the size 35, .04 taper model (maximal 1.3 MPa). In the case of the two occlusal forces, the Lightspeed size 60 apical enlargement was associated with the greatest stress distribution in the apical region. The greatest stress and the most obvious stress difference between the models appeared at the tip of the root when occlusal and vertical compaction loads were applied.
Apical enlargement caused stress distribution changes in the apical region of roots. The larger apical size led to higher stress concentration at the root apex.
通过有限元分析研究并比较两种根管器械预备方法对根管根尖区在根管内牙胶加压和牙合向负载下的根尖应力分布的影响。
重建下颌第一前磨牙的三个有限元分析模型：原始根管模型、35 号、0.04 锥度根管扩大模型和 Lightspeed 60 号根管扩大模型。将 15N 的压缩力垂直施加到距根尖 5mm 的牙胶上。模拟两种方向（垂直和与牙齿纵轴成 45°）的 175N 牙合向负载。计算并比较三个模型中根尖 2mm 处的应力。
在垂直加压下，Lightspeed 60 号（最大 3.3MPa）根管预备的根尖管内的应力高于 35 号、0.04 锥度模型（最大 1.3MPa）。在两种牙合力的情况下，Lightspeed 60 号根尖扩大与根尖区最大的应力分布有关。当施加牙合向和垂直加压负载时，最大的应力和最明显的模型间的差异出现在根尖处。
根尖扩大导致根尖区的应力分布发生变化。较大的根尖尺寸导致根尖处的应力集中更高。
