Department of Prosthodontics, Cukurova University, Adana, Turkey.
J Prosthet Dent. 2011 Jun;105(6):394-402. doi: 10.1016/S0022-3913(11)60081-4.
Because noble dental casting alloys for metal ceramic restorations have a wide range of mechanical properties, knowledge of these properties is needed for rational alloy selection in different clinical situations where cast metal restorations are indicated.
The purpose of this study was to compare the mechanical properties and examine both the fracture and polished surfaces of 6 noble casting alloys that span many currently marketed systems. Five alloys were designed for metal ceramic restorations, and a sixth Type GPT has Type IV alloy for fixed prosthodontics (Maxigold KF) was included for comparison.
Specimens (n=6) meeting dimensional requirements for ISO Standards 9693 and 8891 were loaded to failure in tension using a universal testing machine at a crosshead speed of 2 mm/min. Values of 0.1% and 0.2% yield strength, ultimate tensile strength, elastic modulus, and percentage elongation were obtained. Statistical comparisons of the alloy mechanical properties were made using 1-way ANOVA and the REGW multiple-range test (α=.05). Following fracture surface characterization using scanning electron microscopy (SEM), specimens were embedded in epoxy resin, polished, and again, examined with the SEM.
When the multiple comparisons were considered, there were generally no significant differences in the elastic modulus, 0.1% and 0.2% offset yield strength, and ultimate tensile strength for the d.SIGN 91 (Au-Pd), d.SIGN 59 (Pd-Ag), Capricorn 15 (Pd-Ag-Au) and Maxigold KF (Au-Ag-Pd) alloys, except that the ultimate tensile strength was significantly lower (P<.05) for Maxigold KF than these other 3 alloys. These 4 mechanical properties were generally significantly lower (P<.05) for Aquarius XH (Au-Pt-Pd) and Brite Gold XH (Au-Pt). The d.SIGN 59 (14.6%) and Capricorn 15 (13.8%) alloys had the highest values of mean percentage elongation, which were not significantly different. Aquarius XH (6.0%) and Maxigold KF (4.2%) had the lower mean values of percentage elongation, which were also not significantly different. The polished and etched surfaces for all alloys revealed equiaxed, fine-grain microstructures, and all fracture surfaces contained casting porosity. Incomplete solidification suggestive of dendritic structures was observed for some alloys. Fracture surfaces were complex, with characteristic features of both brittle and ductile fracture. Precipitate particles on the fracture surfaces indicated the multi-phase character of the alloys.
For the important mechanical property of yield strength, there were generally no significant differences among the Au-Pd, Pd-Ag, Pd-Ag-Au and Au-Ag-Pd alloys. Wide variation was found in percentage elongation, with the Pd-Ag and Pd-Ag-Au alloys having the highest values and the Au-Pd-Pt and Au-Ag-Pd alloys having the lowest values.
由于用于金属陶瓷修复体的牙科铸造合金具有广泛的机械性能，因此需要了解这些性能，以便在需要铸造金属修复体的不同临床情况下进行合理的合金选择。
本研究的目的是比较 6 种具有不同商业系统的贵金属铸造合金的机械性能，并观察它们的断裂面和抛光面。其中 5 种合金设计用于金属陶瓷修复体，另一种第六种类型的 GPT（Maxigold KF）用于固定义齿修复，也包括在内进行比较。
根据 ISO 标准 9693 和 8891 的尺寸要求，使用万能试验机以 2mm/min 的十字头速度对试样进行拉伸至破坏试验。获得 0.1%和 0.2%屈服强度、极限拉伸强度、弹性模量和伸长率等数值。使用单因素方差分析和 REGW 多重范围检验（α=.05）对合金力学性能进行统计比较。在使用扫描电子显微镜（SEM）对断裂面特征进行描述后，将试样嵌入环氧树脂中，进行抛光，并再次使用 SEM 进行观察。
在进行多次比较时，除了 Maxigold KF 的极限拉伸强度明显低于（P<.05）其他 3 种合金外，d.SIGN 91（Au-Pd）、d.SIGN 59（Pd-Ag）、Capricorn 15（Pd-Ag-Au）和 Maxigold KF（Au-Ag-Pd）合金的弹性模量、0.1%和 0.2%屈服强度和极限拉伸强度通常没有显著差异。Aquarius XH（Au-Pt-Pd）和 Brite Gold XH（Au-Pt）合金的 4 种机械性能通常明显较低（P<.05）。d.SIGN 59（14.6%）和 Capricorn 15（13.8%）合金的平均伸长率最高，且无显著差异。Aquarius XH（6.0%）和 Maxigold KF（4.2%）的平均伸长率最低，且无显著差异。所有合金的抛光和蚀刻表面均显示出等轴、细晶粒微观结构，所有断裂表面均包含铸造孔隙。一些合金中观察到不完全凝固，提示存在枝晶结构。断裂表面复杂，具有脆性和韧性断裂的特征。断裂表面上的析出颗粒表明合金的多相特性。
对于屈服强度这一重要的力学性能，Au-Pd、Pd-Ag、Pd-Ag-Au 和 Au-Ag-Pd 合金之间通常没有显著差异。伸长率的变化范围较大，Pd-Ag 和 Pd-Ag-Au 合金的伸长率最高，而 Au-Pd-Pt 和 Au-Ag-Pd 合金的伸长率最低。
