Hermann Ilja, Bhowmick Sanjit, Lawn Brian R
Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8500, USA.
J Biomed Mater Res B Appl Biomater. 2007 Jul;82(1):115-21. doi: 10.1002/jbm.b.30712.
A study is made of veneer failure by cracking in all-ceramic crown-like layer structures. Model trilayers consisting of a 1 mm thick external glass layer (veneer) joined to a 0.5 mm thick inner stiff and hard ceramic support layer (core) by epoxy bonding or by fusion are fabricated for testing. The resulting bilayers are then glued to a thick compliant polycarbonate slab to simulate a dentin base. The specimens are subjected to cyclic contact (occlusal) loading with spherical indenters in an aqueous environment. Video cameras are used to record the fracture evolution in the transparent glass layer in situ during testing. The dominant failure mode is cone cracking in the glass veneer by traditional outer (Hertzian) cone cracks at higher contact loads and by inner (hydraulically pumped) cone cracks at lower loads. Failure is deemed to occur when one of these cracks reaches the veneer/core interface. The advantages and disadvantages of the alumina and zirconia core materials are discussed in terms of mechanical properties-strength and toughness, as well as stiffness. Consideration is also given to the roles of interface strength and residual thermal expansion mismatch stresses in relation to the different joining methods.
对全瓷冠层状结构中因开裂导致的饰面破坏进行了一项研究。制作了由1毫米厚的外部玻璃层（饰面）通过环氧树脂粘结或熔融与0.5毫米厚的内部坚硬陶瓷支撑层（核）连接而成的模型三层结构进行测试。然后将所得的双层结构粘贴到厚的柔性聚碳酸酯板上以模拟牙本质基底。在水环境中用球形压头对试样进行循环接触（咬合）加载。在测试过程中使用摄像机原位记录透明玻璃层中的断裂演变。主要的破坏模式是在较高接触载荷下由传统的外部（赫兹）锥形裂纹以及在较低载荷下由内部（液压泵出）锥形裂纹导致玻璃饰面出现锥形开裂。当这些裂纹之一到达饰面/核界面时，即视为发生破坏。从机械性能——强度、韧性以及刚度方面讨论了氧化铝和氧化锆核材料的优缺点。还考虑了界面强度和残余热膨胀失配应力在不同连接方法中的作用。
