Shemtov-Yona K, Rittel D
Faculty of Mechanical Engineering Technion, 32000 Haifa, Israel.
Faculty of Mechanical Engineering Technion, 32000 Haifa, Israel.
J Mech Behav Biomed Mater. 2016 Sep;62:636-644. doi: 10.1016/j.jmbbm.2016.05.028. Epub 2016 Jun 4.
Metallic dental implants are exposed to various intraoral environments and repetitive loads during service. Relatively few studies have systematically addressed the potential influence of the environment on the mechanical integrity of the implants, which is therefore the subject of this study. Four media (groups) were selected for room temperature testing, namely dry air, saliva substitute, same with 250ppm of fluoride, and saline solution (0.9%). Monolithic Ti-6Al-4V implants were loaded until fracture, using random spectrum loading. The study reveals that the only aggressive medium of all is the saline solution, as it shortens significantly the spectrum fatigue life of the implants. The quantitative scanning electron fractographic analysis indicates that all the tested implants grew fatigue cracks of similar lengths prior to catastrophic fracture. However, the average crack growth rate in the saline medium was found to largely exceed that in other media, suggesting a decreased fracture toughness. The notion of a characteristic timescale for environmental degradation was proposed to explain the results of our spectrum tests that blend randomly low and high cycle fatigue. Random spectrum fatigue testing is powerful technique to assess and compare the mechanical performance of dental implants for various designs and/or environments.
金属牙种植体在使用过程中会暴露于各种口腔内环境并承受反复载荷。相对较少的研究系统地探讨了环境对种植体机械完整性的潜在影响，因此本研究以此为主题。选择了四种介质（组）进行室温测试，即干燥空气、唾液替代品、含250ppm氟化物的唾液替代品以及盐溶液（0.9%）。采用随机谱加载对整体式Ti-6Al-4V种植体加载直至断裂。研究表明，所有介质中唯一具有侵蚀性的是盐溶液，因为它显著缩短了种植体的谱疲劳寿命。定量扫描电子断口分析表明，所有测试的种植体在灾难性断裂前都产生了长度相似的疲劳裂纹。然而，发现盐溶液介质中的平均裂纹扩展速率大大超过其他介质，这表明断裂韧性降低。提出了环境降解特征时间尺度的概念来解释我们融合随机低周疲劳和高周疲劳的谱测试结果。随机谱疲劳测试是评估和比较各种设计和/或环境下牙种植体机械性能的有力技术。
