ARTORG Centre for Biomedical Engineering Research, University of Bern, Stauffacherstrasse 78, 3014, Bern, Switzerland.
ARTORG Centre for Biomedical Engineering Research, University of Bern, Stauffacherstrasse 78, 3014, Bern, Switzerland.
J Mech Behav Biomed Mater. 2019 Oct;98:301-310. doi: 10.1016/j.jmbbm.2019.06.024. Epub 2019 Jun 28.
The assessment of dental implant performance is dominated by the concept of mechanical stability. Primary stability is defined as the capacity of a bone-implant structure to bear loads without occurrence of excessive damage and loosening. In order to achieve the highest primary stability, dental implants are inserted into bone using a press-fit procedure. Pre- and postoperative evaluation of primary stability using implantation torque and resonance frequency analysis are valid approaches but do not allow the systematic comparison of different protocols in similar situations. The aim of this research is to develop and validate an explicit, micro-finite element (μFE) methodology to study the effect of different amounts of initial press-fit on implantation torque and initial stiffness of a dental implant. Ten bovine trabecular bone samples were prepared that cover a wide range of bone volume fraction. A dental implant was inserted using two implantation protocols named soft (small initial drilled hole) and dense (increased initial drilled hole). The implantation torque was measured and the stiffness was calculated using an infinitesimal off-axis loading. Finite element simulations of the implant insertion and subsequent loading were performed on micro-computed tomography (μCT) reconstructions of the samples using an explicit solver. Bone was defined as an elasto-plastic material with von Mises yield criteria and hardening. Element deletion was triggered by a threshold in cumulated plastic strains. A sensitivity analysis was performed on friction, hardening and fracture strain to provide a better insight into the effects of these parameters on the results. The implantation torque required for the soft protocol was higher compared to the dense approach in both experiment and simulation due to the higher amount of bone compaction in the first approach. Interestingly, stiffness did not show a significant dependency on the drilling protocol in both experiment and simulation. In conclusion, the explicit microFE methodology developed in this study was able to capture the outcome of two drilling protocols in terms of torque and stiffness and represents a powerful tool to explore the effect of different parameters on primary stability of dental implants.
种植体性能的评估主要基于机械稳定性的概念。初始稳定性被定义为骨-种植体结构在不发生过度损坏和松动的情况下承受载荷的能力。为了获得最高的初始稳定性，种植体使用压配合程序插入骨中。使用植入扭矩和共振频率分析对初始稳定性进行术前和术后评估是有效的方法，但不能在类似情况下对不同方案进行系统比较。本研究的目的是开发和验证一种显式的、微观有限元（μFE）方法，以研究不同初始压配合量对种植体植入扭矩和初始刚度的影响。准备了十个牛骨小梁样本，涵盖了广泛的骨体积分数范围。使用两种植入方案（软方案和密植方案）插入种植体。测量植入扭矩，使用微偏离加载计算初始刚度。使用显式求解器对样本的微计算机断层扫描（μCT）重建进行了种植体插入和随后加载的有限元模拟。将骨骼定义为具有 von Mises 屈服准则和强化的弹塑性材料。通过累积塑性应变的阈值触发元素删除。对摩擦、强化和断裂应变进行了敏感性分析，以更深入地了解这些参数对结果的影响。由于第一种方法中骨的压实量较大，因此软方案所需的植入扭矩高于密植方案，无论是在实验还是模拟中都是如此。有趣的是，在实验和模拟中，刚度都没有表现出对钻孔方案的显著依赖性。总之，本研究中开发的显式微 FE 方法能够捕捉到两种钻孔方案在扭矩和刚度方面的结果，是探索不同参数对种植体初始稳定性影响的有力工具。
