Carr A B, Cai Z, Brantley W A, Mitchell J C
College of Dentistry, Ohio State University, Columbus.
Int J Prosthodont. 1993 May-Jun;6(3):233-41.
Castings simulating a maxillary central incisor coping were fabricated from five representative high-palladium alloys, using burnout temperatures of 1,400 degrees F and 1,500 degrees F, with a carbon-free phosphate-bonded investment. Three castings of each alloy were individually prepared at each burnout temperature. Each casting was sectioned into two specimens, and one specimen was subjected to simulated porcelain firing heat treatment. Polished and etched specimens in as-cast and heat-treated conditions were examined with optical and scanning electron microscopes. Mean values of Vickers hardness (1-kg load) were determined for each alloy and condition. It was observed that the simulated porcelain firing cycles caused major changes in as-cast bulk microstructures for the three first-generation alloys, while only subtle alterations were observed for the two second-generation alloys. In addition, complex regions associated with oxidation processes were found near the surfaces of all the heat-treated alloys. While the as-cast microstructure and the hardness of each alloy did not vary appreciably for the two burnout temperatures, the incidence of hot tearing in one first-generation alloy was substantially reduced at the lower burnout temperature. Statistically significant decreases in hardness generally occurred in the high-palladium alloys after the simulated porcelain firing cycles, but the relatively small changes (usually 10% or less) should not have any clinical significance. Other clinically relevant applications are also discussed.
使用无碳磷酸盐粘结包埋料，在1400华氏度和1500华氏度的焙烧温度下，由五种代表性的高钯合金制作模拟上颌中切牙冠套的铸件。每种合金在每个焙烧温度下分别制备三个铸件。每个铸件被切成两个试样，其中一个试样进行模拟烤瓷烧制热处理。对铸态和热处理状态下的抛光和蚀刻试样用光学显微镜和扫描电子显微镜进行检查。测定每种合金和状态下的维氏硬度（1千克载荷）平均值。观察到模拟烤瓷烧制循环对三种第一代合金的铸态整体微观结构造成了重大变化，而对两种第二代合金仅观察到细微改变。此外，在所有热处理合金的表面附近发现了与氧化过程相关的复杂区域。虽然两种焙烧温度下每种合金的铸态微观结构和硬度没有明显变化，但在较低焙烧温度下，一种第一代合金的热裂发生率大幅降低。模拟烤瓷烧制循环后，高钯合金的硬度通常出现统计学上的显著下降，但相对较小的变化（通常为10%或更小）不应具有任何临床意义。还讨论了其他临床相关应用。
