Development of Dental Alloys alternative to Ag-Pd-Cu-Au Alloys

实验制备了不同化学成分的无Pd银-金-铂-铜合金，以替代传统的牙科用银-钯-铜-金合金。用差示扫描量热法(DSC)测定了相线和相线温度。用分光光度比色法研究了其光学性质，并对其在0.1%Na2S溶液中的抗变色性进行了定量。取得的主要成果如下：1.研究成果。在Au含量相同的合金中，随着铜含量的增加，液、固相线温度均降低。随着铜含量的增加，凝固温度范围变窄。在所有实验合金中，由于光的有效吸收，长波区的光谱反射率较高，而短波区的光谱反射率很低。在相同铜含量的合金中，随着Au含量的增加，吸收边系统地向长波方向移动。同时，随着Au含量的增加，长波区的光谱反射率略有下降。由于光谱反射曲线的这些系统变化，色度指数b^*(黄蓝色)明显增加，使合金带有金色色彩。在相同铜含量为15at.%和20at.%的合金中，随着Au含量的增加，合金在0.1%Na2S溶液中的抗变色性显著提高。在CIELAB颜色空间的L^*，a^*，b^*三个坐标中，L^*值的减小有效地影响了变色测试溶液中材料的颜色变化ΔE^*。

Experimental Pd-free Ag-Au-Pt-Cu alloys with various chemical compositions were prepared to substitute for traditional dental Ag-Pd-Cu-Au alloys. Liquidus and solidus temperatures were determined from DSC data. Spectrophotometric colorimetry was performed to investigate the optical properties and to quantify the tarnish resistance in the 0.1% Na_2S solution. Principal results obtained are as follows.1. In the alloys with the same Au content, both liquidus and solidus temperatures lowered with increasing Cu content. Solidification temperature range became narrow with increasing Cu content.2. In all the experimental alloys, spectral reflectance was high in the long-wavelength region and very low in the short-wavelength region due to the effective absorption of light.3. In the alloys with the same Cu content, the absorption edge systematically moved towards longer wavelength direction with increasing Au content. Simultaneously, spectral reflectance in the long-wavelength region slightly decreased with increasing Au content. Owing to these systematic variations of spectral reflectance curves, chromaticity index b^* (yellow-blue) apparently increased, giving a gold tinge to the alloy.4. In the alloys with the same Cu content of 15 at.% or 20 at.%, tarnish resistance of the alloys in the 0.1% Na_2S solution was markedly improved with Au content.5. Among the three coordinates, L^*, a^*, b^*, in the CIELAB color space, decrease in L^*-value effectively affected the color change, ΔE^*, of the material in the tarnish test solution.