Objectives

Conical implant-abutment connections are popular for its anti-bending performance; on the other hand, the torsional and axial forces also play important roles in occlusion. However, so far there were scarce studies on their effects on connection stability. Therefore, this study seeks to investigate the mechanical performance of conical connections under different cyclic loading conditions.

Methods

15 conical implant-abutment assembles (Cowell Medi, Busan, South Korea) were divided into 3 groups according to different cyclic loadings. In group BTA, the loading condition of the posterior occlusion was simulated (20–200 N, 30° off-axis and 4 mm eccentric to implant axis), generating a bending moment, a torsional moment, and an axial loading. In group BT, a bending moment and a torsional moment of the posterior occlusion were applied (10–100 N, 90° off-axis and 4 mm eccentric to implant axis). In group B, only a bending moment was applied (10–100 N, 90° off-axis and through implant axis). The fatigue testing machine ran at 10 Hz until failure, or to the upper limit of 10⁶ cycles. The fatigue cycles and failure modes were recorded. Besides, the value of the torque loss of the abutment screw, the difference between initial torque and post-load reverse torque, was calculated. The data were statistically analyzed. Morphologies of the abutment conical surface were examined by scanning electron microscopy.

Results

In group B and BTA, all samples passed the test (10⁶ cycles). While, in group BT, all abutments generated rotation within 140 cycles, showing significant differences compared to the other two groups (p < 0.001). However, from SEM observations, both group B and BT showed marked fretting wear, indicating obvious micromotion in the connection. Whereas group BTA showed indentation of tight contact, attributed to the axial loading. In terms of the torque loss of the abutment screw, the torque loss in group BT was much more than the other two groups with statistically significant differences (p < 0.05).

Conclusion

Owing to the effect of the bending moment, marked fretting wear was generated in the conical connections and further led to loss of the anti-torsional ability. However, adding an axial loading could improve their anti-torsional ability significantly.

中文翻译：

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圆锥形种植体-基台连接在不同循环载荷条件下的机械性能。

目标

圆锥形种植体-基台连接因其抗弯曲性能而广受欢迎。另一方面，扭转力和轴向力在咬合中也起着重要作用。但是，到目前为止，关于它们对连接稳定性的影响的研究很少。因此，本研究旨在研究锥形连接在不同循环载荷条件下的机械性能。

方法

根据不同的循环载荷，将15个圆锥形种植体-基台组件（Cowell Medi，韩国釜山）分为3组。在BTA组中，模拟了后牙咬合的负载情况（20-200 N，离轴30°，相对于植入物轴的偏心距4 mm），产生弯曲力矩，扭转力矩和轴向负载。在BT组中，施加了后牙咬合的弯曲力矩和扭转力矩（10–100 N，离轴90°，相对于种植体轴偏心4 mm）。在B组中，仅施加了弯矩（10–100 N，离轴90°并穿过种植体轴）。疲劳试验机以10 Hz的频率运行直到失效，或者达到10 ^6的上限周期。记录疲劳周期和失效模式。此外，计算了基台螺丝的扭矩损失值，即初始扭矩和负载后反向扭矩之间的差。对数据进行统计分析。通过扫描电子显微镜检查基台锥形表面的形貌。

结果

在B组和BTA组中，所有样品均通过了测试（10 ⁶个循环）。而在BT组中，所有基台均在140个周期内产生旋转，与其他两组相比显示出显着差异（p  <0.001）。但是，从SEM观察，B组和BT组均显示出明显的微动磨损，表明连接中存在明显的微动。而BTA组显示出紧密接触的凹痕，这归因于轴向载荷。就基台螺丝的扭矩损失而言，BT组的扭矩损失远多于其他两组，具有统计学上的显着差异（p <0.05）。

结论

由于弯矩的作用，在锥形连接中产生明显的微动磨损，并进一步导致抗扭能力的损失。但是，增加轴向载荷可以显着提高其抗扭能力。