Lassila L V, Vallittu P K
University of Kuopio, Kuopio and University of Turku, Turku, Finland.
J Prosthet Dent. 1998 Dec;80(6):708-13. doi: 10.1016/s0022-3913(98)70059-9.
Fatigue of denture clasp alloys causes clasp failures and decreases the retention of removable partial dentures. Little information is available on how the environment (dry, water, artificial saliva) effects the fatigue behavior of cast cobalt-chromium alloy clasps.
This study determined the effect of water and the artificial saliva on the resistance of cast cobalt-chromium alloy to the deflection fatigue.
Test bars (n = 10) were tested either dry, in water, or in artificial saliva (Fusayama type) with a constant deflection fatigue test. The number of loading cycles before fracture was registered as resistance to fatigue. To establish whether there were indications of alloy corrosion occurring during the fatigue test, the testing liquid was analyzed retrospectively with an atomic absorbance spectroscopy. To determine elemental composition of the fracture surface, fracture surfaces of the test bars were analyzed with a scanning electron microscope and energy dispersive spectroscopy.
The bars that were tested dry had a mean fatigue resistance of 78,000 loading cycles, whereas test specimens tested in artificial saliva had a resistance of 59,000 loading cycles and 36, 000 for those tested in water. Atomic absorbance spectroscopy revealed small amounts of cobalt (Co) in testing water and in artificial saliva. Energy dispersive spectroscopy analysis revealed differences in elemental composition of a fatigue fracture surface compared with that of a 1-bend fracture.
The results suggest that both water and artificial saliva reduce the fatigue strength of cobalt-chromium alloy, explained by corrosion of the alloy in the wet environment.
义齿卡环合金的疲劳会导致卡环失效，并降低可摘局部义齿的固位力。关于环境（干燥、水、人工唾液）如何影响铸造钴铬合金卡环的疲劳行为，目前可用信息较少。
本研究确定水和人工唾液对铸造钴铬合金抗挠曲疲劳性能的影响。
测试棒（n = 10）分别在干燥、水或人工唾液（舟山市釜山本松型）中进行恒定挠曲疲劳试验。将断裂前的加载循环次数记录为抗疲劳性能。为确定在疲劳试验期间是否有合金腐蚀迹象，对试验液体进行回顾性原子吸收光谱分析。为确定断裂表面的元素组成，用扫描电子显微镜和能谱分析测试棒的断裂表面。
干燥状态下测试的棒材平均抗疲劳性能为78,000次加载循环，而在人工唾液中测试的试样抗疲劳性能为59,000次加载循环，在水中测试的为36,000次加载循环。原子吸收光谱显示试验用水和人工唾液中有少量钴（Co）。能谱分析显示疲劳断裂表面的元素组成与一次弯曲断裂表面存在差异。
结果表明，水和人工唾液都会降低钴铬合金的疲劳强度，这可由合金在潮湿环境中的腐蚀来解释。
