Faculty of Dentistry, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
Clin Exp Dent Res. 2022 Dec;8(6):1496-1504. doi: 10.1002/cre2.645. Epub 2022 Aug 8.
To investigate the fatigue behavior of cast and laser-sintered cobalt-chromium (CoCr) and polyetheretherketone (PEEK) material for a removable partial denture (RPD) clasps.
Dumbbell-shaped specimens were digitally designed with the center part of the dumbbell being a half-round shape at the cross-sectional dimension of 1.25 mm to simulate a typical clasp design and dimensions. A fatigue machine with an offset axis rotation system simulated a typical undercut depth of 0.25, 0.50, and 0.75 mm. Each group was subjected to 30,000 fatigue cycles (simulating 21 years) or till specimen failure. Before testing, the stress value at each undercut depth for each specimen was established in a universal testing machine and SN curves were plotted for each group. Data were statistically analyzed using Kruskal-Wallis and post hoc tests. The fractured surfaces were analyzed using SEM.
The average fatigue cycles with 0.25, 0.50, and 0.75 mm undercuts were 27,155 ± 6277, 9298 ± 4033, 5642 ± 8785 for cast CoCr and 26,765 ± 6150, 11,318 ± 7931, 2861 ± 4803, for laser-sintered CoCr, respectively. Apart from three specimens, the PEEK groups did not fail during the simulation period. Clasps with 0.25 mm deflection showed significantly higher fatigue resistance than other groups (p < .001). There was no significant difference in fatigue behavior between the cast and laser-sintered CoCr. Microporosities at the fractured site along with irregular crack propagation were observed for cast and laser-sintered CoCr specimens. Fatigue-induced broken polymer crosslinking chains were observed in PEEK specimens.
PEEK material exhibited the highest fatigue resistance and significantly lower deflection resistance. Cast and laser-sintered CoCr showed similar fatigue resistance and behavior.
研究铸造和激光烧结钴铬（CoCr）和聚醚醚酮（PEEK）材料用于可摘局部义齿（RPD）卡环的疲劳行为。
使用数字设计制作哑铃形试件，哑铃的中心部分在横截面上为半圆形，尺寸为 1.25mm，模拟典型的卡环设计和尺寸。采用带有偏置轴旋转系统的疲劳机模拟典型的 0.25、0.50 和 0.75mm 的倒扣深度。每组试件分别进行 30000 次疲劳循环（模拟 21 年）或直至试件失效。在测试前，在万能试验机上确定每个倒扣深度下每个试件的应力值，并绘制每组试件的 SN 曲线。使用 Kruskal-Wallis 和事后检验对数据进行统计学分析。使用扫描电子显微镜（SEM）分析断裂面。
具有 0.25、0.50 和 0.75mm 倒扣的平均疲劳循环次数分别为铸造 CoCr 的 27155±6277、9298±4033 和 5642±8785，激光烧结 CoCr 的 26765±6150、11318±7931 和 2861±4803。除了三个试件外，PEEK 组在模拟期间没有失效。具有 0.25mm 挠度的卡环显示出明显更高的疲劳阻力（p<0.001）。铸造 CoCr 和激光烧结 CoCr 的疲劳行为没有显著差异。铸造和激光烧结 CoCr 试件的断裂部位存在微孔和不规则的裂纹扩展。在 PEEK 试件中观察到疲劳诱导的聚合物交联链断裂。
PEEK 材料表现出最高的疲劳阻力和明显更低的挠度阻力。铸造和激光烧结 CoCr 表现出相似的疲劳阻力和行为。
