Mueller H J, Lenke J W, Bapna M S
American Dental Association, University of Illinois, Chicago 60611.
Scanning Microsc. 1988 Jun;2(2):777-87.
Six crown and bridge alloys ranging in nobility between 25-63 wt % (18-45 at %) were analyzed by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and secondary ion mass spectroscopy (SIMS), as well as by Lab* colorimetry before and after in vitro tarnishing in artificial saliva with and without additions of 0.00016, 0.016, and 1.6 % Na2S with a rotating wheel apparatus. All alloys except the lowest of 18 at % changed colors to about the same degree after 72 h of tarnishing. All alloys decreased in L*, while increased in both a* and b*, thus appearing darker and with increased redness and yellowness. This was due to localized darkening and to other products. For all alloys except one, saliva without sulfide promoted color changes more severe than for saliva with 0.016 % Na2S. For the most part, analysis by EDS was unable to detect differences between the tarnished films and the as-polished surfaces. SIMS analysis, however, showed changes in the substrate ion (Cu, Ag, Pd, and In) peak intensities. In most cases the intensities decreased and with the decrease greater with the sulfide-free saliva than with sulfide-containing. This indicated that sulfide promoted insoluble deposition of products. Changes in the Ag, Pd, and In peak intensities followed much the same pattern as with Cu. The as-polished surfaces, even though carefully prepared, showed much contamination in the form of organics, namely C, CH, N, NH, O, CHN, CN, as well as from Na, K, Ca, Si, S, Cl, and others. Most tarnished surfaces showed large increases in Na, K, and Ca, and with the sulfide-free saliva being more severe in this regard. The mass spectrum also showed peaks with atomic mass units in the range 55-58 related to only some of the tarnished surfaces.
对六种贵金属含量在25 - 63 wt%（18 - 45 at%）之间的冠桥合金进行了分析，分析方法包括光学显微镜、扫描电子显微镜（SEM）、能谱仪（EDS）和二次离子质谱仪（SIMS），同时还在添加和不添加0.00016%、0.016%和1.6%硫化钠（Na2S）的人工唾液中，使用转轮装置进行体外 tarnishing 前后，通过Lab比色法进行分析。除了最低的18 at%的合金外，所有合金在 tarnishing 72小时后颜色变化程度大致相同。所有合金的L值降低，而a值和b值均增加，因此看起来颜色变深，红色和黄色增加。这是由于局部变黑和其他产物导致的。对于除一种合金外的所有合金，无硫化物的唾液比含有0.016% Na2S的唾液更能促进颜色变化。在大多数情况下，EDS分析无法检测到 tarnished 膜与抛光表面之间的差异。然而，SIMS分析显示了基体离子（Cu、Ag、Pd和In）峰强度的变化。在大多数情况下，强度降低，且无硫化物唾液导致的强度降低比含硫化物的唾液更大。这表明硫化物促进了产物的不溶性沉积。Ag、Pd和In峰强度的变化与Cu的变化模式大致相同。即使经过精心制备，抛光表面仍显示出大量以有机物形式存在的污染物，即C、CH、N、NH、O、CHN、CN，以及Na、K、Ca、Si、S、Cl等。大多数 tarnished 表面的Na、K和Ca含量大幅增加，在这方面无硫化物唾液更为严重。质谱还显示，只有部分 tarnished 表面出现了原子质量单位在55 - 58范围内的峰。
