Statement of problem

The mechanical behavior of the conical connection implant with different torque levels requires evaluation.

Purpose

The purpose of this finite element analysis study was to investigate the impact of abutment screw torque on the formation of microgaps at the implant-to-abutment interface of a conical connection under oblique loading. This is important because it is thought that bacteria can invade the internal implant space through the abutment-implant microgaps, causing peri-implantitis.

Material and methods

Three-dimensional finite element analyses of the conical implant-abutment connection were performed by using screw torques of 20 Ncm and 30 Ncm. Oblique loads from 10 N to 280 N were applied to the prosthesis placed on the implant. The maximum von Mises stress in the abutment screw, the microgap formation process, and the critical load for bridging the internal implant space were evaluated.

Results

The stresses in the abutment screw under oblique loading had limited sensitivity to the screw torque. However, the residual stress in the screw with a 30-Ncm torque was 35% higher than that with a 20-Ncm torque in the absence of an external load. The area in contact at the implant-to-abutment interface decreased with increasing load for both torque values. The critical load for bridging the internal implant space was 160 N for a screw torque of 20 Ncm and 220 N for a screw torque of 30 Ncm. The maximum gap size was approximately 470 μm with all the loads.

Conclusions

Increasing the screw torque can reduce the formation of microgaps at the implant-to-abutment interface. However, this will result in higher mean stress in the abutment screw, which may reduce its fatigue life and consequently that of the prosthesis. Further research is needed to evaluate the relationship between the abutment screw torque and microleakage in implant-supported restorations.

中文翻译：

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拧紧扭矩对螺钉应力和种植体基台微间隙形成的影响：有限元分析

问题陈述

需要对不同扭矩水平的锥形连接植入物的机械性能进行评估。

目的

这项有限元分析研究的目的是研究基台螺钉扭矩对倾斜载荷下锥形连接的种植体与基台界面处微间隙形成的影响。这很重要，因为人们认为细菌可以通过基台-种植体微间隙侵入内部种植体空间，导致种植体周围炎。

材料与方法

使用 20 Ncm 和 30 Ncm 的螺钉扭矩对锥形种植体-基台连接进行三维有限元分析。将 10 N 到 280 N 的斜向载荷施加到放置在植入物上的假体上。评估了基台螺钉中的最大 von Mises 应力、微间隙形成过程以及桥接内部种植体空间的临界载荷。

结果

斜向载荷下基台螺钉中的应力对螺钉扭矩的敏感性有限。然而，在没有外部负载的情况下，30-Ncm 扭矩的螺钉中的残余应力比 20-Ncm 扭矩高 35%。对于两个扭矩值，种植体与基台界面的接触面积随着负载的增加而减小。对于 20 Ncm 的螺钉扭矩和 30 Ncm 的螺钉扭矩，桥接内部种植体空间的临界载荷为 160 N。所有负载的最大间隙尺寸约为 470 μm。

结论

增加螺钉扭矩可以减少种植体与基台界面处微间隙的形成。然而，这将导致基台螺钉的平均应力更高，这可能会降低其疲劳寿命，从而降低假体的疲劳寿命。需要进一步的研究来评估种植体支持的修复体中基台螺钉扭矩和微渗漏之间的关系。