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Quantitative Evaluation of Chemical Stability of Dental Alloys

牙科合金化学稳定性的定量评价

基本信息

批准号：
63470123
负责人：
OHTA Michio
金额：
$ 3.26万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

The purpose of this study was to evaluate the chemical stability of dental alloys quantitatively.Corrosion resistivity was expressed by the parameter Q which correspond to the total amount of electrochemical reaction occurred on the specimen surface. Tarnish resistance was evaluated by color difference DELTAE between those of prior and after testing.Principal results were summarized as follows;(1) Corrosion behavior of alloys with single phase structure were principally determined by the nobility of the alloy.(2) Anodic potentiodynamic polarization curves of the alloys with multiphase structure were rather complicated. Characteristic potential (Ec) at which corrosion rate increased spontaneously appeared at two different potentials. But these complicated curves can be explained by superposing two simple curves of each single phase. Two different Ec correspond to those of each phase, and current density at a potential can be expressed by the arithmetical mean of those of each phase.(3) DELTAE of alloys. in which a part of gold was replaced with palladium up to about 10at%, decreased with palladium content. But further replacement increased AE. This increase in DELTAE was attributed to the decrease in chemical stability by the replacement of gold with palladium. Decrease in DELTAE by the addition of small amount of palladium may be explained by the mechanism of palladium enrichment just below the sulfide layer. This enrichment may suppress the diffusion of S^<--> ion. resulting in the decrease in the growth rate of sulfide layer.(4) Tarnish susceptibility of low-nobility alloy was very sensitive to its microstructure. Phase separation increased DELTAE to about two times of homogenized single phase state. But a small amount of palladium addition improved this tarnish sensitivity of dual phase alloy. This may be attributed to the enrichment of palladium in the copper-rich phase.

本研究的目的是定量评价牙科合金的化学稳定性，用表征试样表面发生电化学反应总量的参数Q来表征合金的耐腐蚀性能。主要结果如下：（1）单相结构合金的腐蚀行为主要取决于合金的贵金属性。(2)具有多相结构的合金的阳极动电位极化曲线较为复杂。在两种不同的电位下，腐蚀速率自发增加的特征电位（Ec）出现。但这些复杂的曲线可以通过叠加每个单相的两条简单曲线来解释。两个不同的Ec对应于每一相的Ec，并且在电势处的电流密度可以由每一相的那些的算术平均值表示。(3)合金的Δ E。其中一部分金被钯置换至约10at%，随着钯含量的增加而降低。但进一步置换会增加AE。Δ E的增加归因于用钯取代金而降低了化学稳定性。通过添加少量的钯，Δ E的降低可以通过钯富集在硫化物层正下方的机理来解释。这种富集可能会抑制S ~+离子的扩散<-->。导致硫化物层的生长速率降低。(4)低贵金属合金的变色敏感性对合金的微观结构非常敏感。相分离使Δ E增加到均匀单相状态的约两倍。但少量钯的加入改善了双相合金的这种变色敏感性。这可能归因于钯在富铜相中的富集。