Bessing C
Department of Dental Materials and Technology, Faculty of Odontology, University of Umeå, Sweden.
Swed Dent J Suppl. 1988;53:1-56.
For economic reasons a large number of cheaper alternatives to the high noble dental casting gold alloys have been introduced on the market. The main problem with these alternative alloys is their chemical stability. This is a most important property as degradation of an alloy may release substances which can be harmful to the wearer. Thus, the corrosion behavior of four dissimilar alternative dental casting alloys together with a high-gold reference alloy was evaluated in the as-cast, hardened, and annealed conditions by means of potentiodynamic polarization analysis, partly supplemented by electron spectroscopy for chemical analysis. In order to facilitate interpretation of the results of the corrosion study, the composition and metallographic structure of specimens in the specimens in the dissimilar conditions had to be determined. The methods used were light microscopy, electron probe microanalysis, and X-ray diffractometry. Biocompatibility, which is related to the release of metal ions, was evaluated by subcutaneous implantation of specimens from the five alloys in guinea-pigs. Thus, the in vivo toxicity of the different alloys could be assessed. The chemical stability of an alloy also determines its tarnish resistance and as tarnish apart from creating esthetic problems, also may result in changes in the wetting characteristics of the alloy surface the in vivo tarnish of as-cast and annealed specimens inserted into complete mandibular dentures was estimated after up to 16 weeks. Castability, an important factor in an alloy's clinical performance, was measured as the marginal sharpness of cast simulated crowns from the five alloys. Finally, the clinical performance of crowns and bridges made from one low-gold and one silver-palladium alloy as experimental materials together with a high-gold alloy as a reference material was evaluated using specific periodontal parameters, a tarnish index, and CDA's guidelines for the assessment of clinical quality. The findings may be summarized as follows: The metallographic evaluation for the low-gold alloys Midas and Rajah indicated that these alloys may contain more than one phase. The two silver-palladium alloys Albacast and Alba V were heterogeneous in the three conditions studied. In most cases, the pre-treatment of the alloys had a decisive influence on their proneness to corrosion. The castability of the silver-palladium alloys was inferior to that of the gold-based alloys. The biocompatibility as revealed by subcutaneous implantation showed that one of the silver-palladium alloys (Albacast) produced the least tissue response, while the other one (Alba V) exhibided the worst tissue response.(ABSTRACT TRUNCATED AT 400 WORDS)
出于经济原因，市场上推出了大量比高纯度牙科铸造金合金便宜的替代品。这些替代合金的主要问题是其化学稳定性。这是一项极其重要的特性，因为合金的降解可能会释放出对佩戴者有害的物质。因此，通过动电位极化分析，并部分辅以化学分析电子能谱，对四种不同的替代牙科铸造合金以及一种高金参考合金在铸态、硬化和退火条件下的腐蚀行为进行了评估。为便于解释腐蚀研究结果，必须确定不同条件下试样的成分和金相结构。所采用的方法有光学显微镜、电子探针微分析和X射线衍射法。通过将五种合金的试样皮下植入豚鼠体内来评估与金属离子释放相关的生物相容性。这样就可以评估不同合金的体内毒性。合金的化学稳定性还决定其抗变色性，而且除了造成美观问题外，变色还可能导致合金表面润湿性的变化，对植入全下颌假牙的铸态和退火试样的体内变色情况进行了长达16周的评估。铸造性能是合金临床性能的一个重要因素，通过测量五种合金铸造模拟冠的边缘清晰度来衡量。最后，以一种低金合金和一种银钯合金作为实验材料，以一种高金合金作为参考材料，使用特定的牙周参数、变色指数以及CDA临床质量评估指南，对用它们制作的冠和桥的临床性能进行了评估。研究结果可总结如下：对低金合金迈达斯和拉贾的金相评估表明，这些合金可能含有不止一个相。两种银钯合金阿尔巴卡斯特和阿尔巴五号在研究的三种条件下都是不均匀的。在大多数情况下，合金的预处理对其腐蚀倾向有决定性影响。银钯合金的铸造性能不如金基合金。皮下植入显示的生物相容性表明，其中一种银钯合金（阿尔巴卡斯特）产生的组织反应最小，而另一种（阿尔巴五号）表现出最差的组织反应。（摘要截选至400字）
