A quantitative and subjective characterization of tarnishing in low-gold alloys.

1. The quantitative objective characterization of tarnish gave results which are identical with those obtained from a blind subjective analysis. 2. The low-gold alloys fall into three classes. The alloy Ney Cast III is superior in performance to the other low golds and approximately equivalent to the high-gold alloy Firmilay. The intermediate alloys, including Midacast, Stabilor G, Mowrey No. 46, Tiffany, and Midas are similar in performance to the high-gold alloy Rx O.R.Y. The low-gold alloys Dent Cast 44, Minigold, and Progold tarnish in a manner which, in our opinion, makes them unacceptable.     

Clinical evaluation of three amalgam alloys

A total of 117 high-copper amalgams of three types (platinum-modified, palladium-modified and dispersed phase) was placed by two operators in 59 patients. Restorations were assessed for marginal fracture, tarnish, corrosion, and tooth staining on continuous linear photographic rating scales. After one year, the platinum- and palladium-modified alloys showed a significant amount of tarnish, and all three alloys had statistically significant marginal fracture. The only significant difference between alloys at one year was the greater tarnish of the platinum-modified alloy. There was no association between static creep and marginal fracture.     

The 8-year clinical performance of 15 low-gold casting alloys

The objectives of this study were to (1) evaluate the clinical performance of low-gold alloys over time, with special attention to tarnish resistance, and (2) determine the influence of compositional factors on performance. A total of 264 restorations were inserted in 50 patients using Modulay (control), Forticast, Midas, Maxigold, Midigold, Minigold, Mowrey 120, Mowrey 46, and 8 experimental alloys (UNC 1–8); 161 (61%) of the original restorations were recalled after an average of 8 years and rated for tarnish, plaque, type of material at contacts, retention of polish, surface porosity, and secondary caries. The incidence of tarnish at ranked locations was relatively low and ranged from 0.004-0.2 on a 0–2 tarnish scale. Low-gold alloys as a group were not significantly more tarnished than the control but there were differences between alloys. Palladium content appears especially important to improved tarnish resistance in alloys with very low gold content. Incidence of plaque accumulation and tarnish was highest in the proximal and cervical one thirds. There was no secondary caries and no surface porosity.     

In vitro corrosion of dental Ag-based alloys in polyvinylpyrrolidone iodine solution

The corrosion and tarnish behaviors of three Ag-based alloys (Ag-Pd-Cu-Au alloy, Ag-In alloy, and Ag-Sn-Zn alloy) in polyvinylpyrrolidone iodine (povidone-iodine) solution were examined. The degree of tarnish was evaluated by visible-ray spectrocolorimetry. Corrosion potential measurements and analyses of corrosion products by X-ray diffractometry were carried out to elucidate the corrosion mechanism. The corrosion rate of the three Ag-based alloys in povidone-iodine solution at its practical concentration used as a gargle solution was so fast that the alloys tarnished within 10 seconds of immersion with the formation of AgI. Thermodynamic consideration and the results of surface analysis by X-ray diffractometry revealed that the main anodic and cathodic reactions were Ag + I(-)-->AgI + e- and I2 + 2e(-)-->2I- respectively.     

Aay4对钛及钛75合金表面失泽腐蚀的研究

目的　研究放线共生放线杆菌血清b型 (Aay4)对钛及钛 75合金种植体表面的失泽腐蚀。方法　将纯钛、钛 75合金机械加工成 10mm× 10mm× 1mm的板片 ,数量分别为 30片和 6 0片 ,取钛 75合金试件 30片与纯钛试件分别进行化学钝化。将钝化纯钛组 30片随机分成空白组、培养基组和实验组 ,每组各 10片。在厌氧环境中将Aay4接种到改良GAM培养基上 ,将试件贴附于表面 ,每周转换传递 1次 ,共 10周。用 0 0 5 %戊二醛灭菌 ,清洗 ,2周后进行色度计观察。结果　肉眼观察见纯钛、钛 75合金 (钝化与非钝化 )的实验组试件表面颜色均由银灰色变成黄色。 3种试件的空白对照与培养基对照组的L 、a 、b 值无显著变化 ;而实验组分别与空白对照组、培养基对照组比较 ,其L 、a 、b 值的差异均有显著性 (P <0 0 5 )。结论　Aay4对钛及钛 75合金 (钝化和非钝化 )均发生肉眼可见的表面失泽。色度计分析表明 ,3种类型的种植体试件表面颜色由绿黄区域落到了红黄区域     

Tarnish and corrosion of a commercial dental Ag-Pd-Cu-Au casting alloy

The correlation between microstructure, tarnish, and corrosion behavior of a commercial dental Ag-Pd-Cu-Au casting alloy after various heat treatments was studied. The attacked structural components were identified by comparing SEM micrographs with light optical micrographs taken after exposure of the alloy to a 2% Na2S solution and after dynamic polarization in de-aerated artificial saliva. The characteristic dynamic polarization curves for the alloy after the heat treatments were established. The results were verified by analogous testing of two experimental alloys with compositions similar to those of the analyzed components in the commercial alloy annealed at 600 degrees C for seven wk. The matrix of the commercial alloy was decomposed, according to the heat treatments, into varying proportions of a tarnish- and corrosion-resistant Cu- and Pd-rich component (A) and a nonresistant Ag-rich component (B). The presence of A considerably increased the tarnish rate of B, due to galvanic coupling. Age-hardening of the alloy increased the proportion of the tarnish- and corrosion-prone component B.     

Gold-nickel alloys in dental prostheses.

A gold-nickel master alloy was prepared by arc melting in an inert atmosphere and from it, mechanical test specimens and dental prostheses were made by centrifugal casting. The cast alloy had a yield strength of about 7,400 kg/cm2, with an elongation of 12%. The alloy was clinically tested in the form of partial dentures and crown and bridge materials. For the 32-month period these prostheses have been in use, no tissue reaction, tarnish, or corrosion had been observed.     

Study of gold-nickel alloy. (Part 1) The properties of gold-nickel binary alloys (author's transl)]

To research the possibility of a new dental Au base alloy, Au-Ni alloys were examined. Comospitions were 82.5% Au-17.5% Ni alloy, 77% Au-23% Ni alloy and 70% Au-30% Ni alloy. Mechanical properties of these alloys were equal to those of hardened Au added Pt alloy or type IV Au alloy. And these alloys have shown no tarnish and corrosion in 0.1% NaS solution, 0.05% HC1 solution or 1% Lactic acid solution after 21 days. Especially 77% Au-23% Ni alloy was the best among them.     

Corrosion behavior of dental alloys in various types of electrolyzed water

The corrosion behavior of dental alloys was examined in electrolyzed strong acid water, weak acid water and neutral water using a 7-day immersion test. The precious metal alloys, gold alloy. Au-Ag-Pd alloy and silver alloy showed the greatest surface color change and dissolution of constituents in the strong acid water and the smallest in the neutral water. The release of Au from gold alloy was especially marked in the strong acid water. Co-Cr alloy showed greater corrosion and tarnish resistance in the strong acid water rather than in the weak acid water and the neutral water. X-ray microanalysis revealed that the corrosion products on the precious metal alloys were silver chloride crystals and the thin brown products on Co-Cr alloy were cobalt and chromium oxides. Ti was sound in all three types of electrolyzed water. The neutral water appeared the least corrosive to metals among the three types showing equivalent bactericidal activity.     

Corrosion and tarnish of dental silver-based alloys in 0.1% Na2S and Ringer's solutions. (Part 1) Electrochemical study

The corrosion behavior of three silver-based alloys, Ag-Sn-Zn, Ag-In, and Ag-Pd-Cu, were investigated by potentiodynamic anodic polarization analysis and the polarization resistance method in 0.1% Na2S and Ringer's solutions. The corrosion activity of the Ag-Sn-Zn alloy was higher in Ringer's solution than in the 0.1% Na2S solution. In contrast, the corrosion rate of the Ag-Pd-Cu alloy was approximately 500 times higher in the 0.1% Na2S solution than in Ringer's solution. The results show that the generally accepted concept that tarnish is merely a surface discoloration due to the deposition of insoluble products is inadequate. The alloy discolors while being severely attacked in the presence of sulfides. For the Ag-In alloy, the corrosion activity in the 0.1% Na2S solution was as high as in Ringer's solution. These silver-based alloys exhibit different electrochemical activities in different solutions. The test solutions for corrosion tests must be carefully chosen for each alloy system through a screening test to replicate the predominant corrosion reaction proceeding in the oral environment.     

Electrochemical characterization of three types of Co-Cr based alloys manufactured by casting and selective laser melting according to ISO 10271

ObjectiveTo characterize the effect of elemental composition and manufacturing process on the electrochemical properties of Co-Cr-Mo, Co-Cr-W and Co-Cr-Mo-W alloys.MethodsSix Co-Cr based alloys were included in this study. All alloys are Co-Cr based alloys, classified in three different types according to their elemental composition. The first group has Mo as the third alloying element while the second one has W instead of Mo. The third one has both alloying elements. The groups are further divided by the manufacturing process (casting or Selective Laser Melting(SLM)). All groups were subjected to static immersion, open circuit potential, anodic scan, SEM/EDX analysis, static and cyclic tarnish testing according to ISO 10271 requirements. The ionic release was evaluated by inductively coupled plasma mass spectrometry and the results were statistically analyzed by two way ANOVA and Tukey test (a=0.05).ResultsNo statistical differences were identified for Co-Cr-Mo alloy for all elements and their total ionic release between casting and SLM manufacturing processes, in contrast to significantly lower values for SLM groups for the other two groups. All groups tested demonstrated similar performance in OCP and AS testing while no gross elemental changes before and after AS were identified following EDX analysis. All alloys fulfilled the requirements of tarnish resistanceConclusionsThe ionic release is dependent on alloy type and manufacturing process while all groups were found to fulfill the requirements of international standards for ionic release, corrosion and tarnish resistance and thus an acceptable clinical performance is anticipated.     

Tarnishing in vivo of Ag-Pd-Cu-Zn alloys

Pre-polished specimens of four Ag-Pd-Cu-Zn alloys have been tested for tarnishing while embedded in full acrylic dentures for from six to eight months in vivo. The results have been compared with those from previous immersion tests using 2% Na2S solutions. In both types of tests, a multiphase alloy consisting of a Pd-Cu-Zn-rich compound in a Ag-rich matrix displayed less corrosion and tarnish resistance than did alloys with compositions similar to the Pd-Cu-Zn-rich compound or the Ag-rich matrix. It is suggested that the presence of local microgalvanic cells due to chemical inhomogeneities caused the observed susceptibility to tarnishing. Sulfur was detected by a microprobe in the tarnish layer developed in the oral cavity. The discoloration on this multiphase alloy covered the interdendritic areas with short distances between the chemical inhomogeneities. This microstructural location was somewhat different from the many dark spots created predominantly on Ag-rich areas during in vitro testing. This difference is most likely due to dissimilar conditions with regard to sulfide ion concentrations, the presence of protein films, and the length of exposure time.     

Valiant-PhD and Lojic N amalgam alloys: four-year clinical results

From 1984 to 1986, 97 similar pairs of Valiant-PhD and Lojic N amalgam restorations were placed at random by one dentist in Class II cavities prepared in 105 molar and 89 premolar permanent teeth of 73 patients treated in a private practice. Assessments were made of the different handling properties of the two alloys and of the effects of polishing, or otherwise, on the clinical behaviour of the restorations. Valiant-PhD alloy had more 'body' for condensing and was easier to carve and polish than was Lojic N alloy. After periods of up to four years, there was only one restoration failure (from bulk fracture) for each alloy although both materials deteriorated over time. Both the polished and the unpolished restorations showed similar deterioration for marginal fracture and staining, and for surface tarnish, and their initially-different surface textures became more similar during the study. Statistically, Lojic N restorations showed significantly more surface tarnish, but less marginal fracture than did Valiant-PhD restorations, and the tarnishing did not appear to be related to the effects of corrosion.     

Corrosion of dental copper, nickel, and gold alloys in artificial saliva and saline solutions

The purpose of this investigation was to study the tarnish and corrosion of three commercial copper alloys, three experimental copper alloys, two nickel alloys, and one high-gold alloy by exposing the specimens for four weeks to artificial saliva and saline solutions. Half of the specimens were brushed, and the solutions were changed regularly. The copper-based and the beryllium-containing nickel alloys exhibited significant surface alterations after exposure to either solution. The potential of elevated release of ions to the oral cavity and to the target organs by some of the investigated alloys should be considered if dental usage of these alloys is to be extended.     

A clinical evaluation of semiprecious alloys for dowels and cores.

The semiprecious metals investigated and hard dental gold alloys may be manipulated in a similar manner. The semiprecious metals produced accurate and well-fitted dowels needing minimal adjustment. Being harder than type III gold alloy, they would be ideal for casting dowels and cores. Before considering these semiprecious alloys as final restorations, however, they must be further examined for resistance to tarnish and corrosion and their marginal adaptability and burnishability.     

新型牙体充填材料—镓合金的抗腐蚀性能研究

目的 研究新型不含汞的牙体充填材料镓合金的抗腐蚀性能。方法 运用电化学方法，以高铜银汞合金为参照，检测镓合金在人工唾液中的电化学腐蚀速度。结果 在人工唾液中镓合金与高铜银汞合金的腐蚀速度无显著性差异（Ｐ〉０．０５）。结论镓合金在人工唾液中具有良好的抗腐蚀性能。     

Tarnish evaluation of gold-based dental alloys

Three commercial gold dental alloys and three ternary (Au-Ag-Cu) alloys of constant nobility were subjected to a standardized test battery for tarnish. The tests included sodium sulfide and artificial saliva solutions, both at 37 degrees C, in sealed containers. Quantitative measurements of tarnish were made from the alloy color change during a three-day exposure. Alloy nobility is a relatively important factor in determining tarnish resistance; however, microstructure can have a negative effect on tarnish resistance. Alloys with a two-phase microstructure produce microgalvanic conditions which lead to either silver chloride or silver sulfide tarnish products. A solution heat treatment improves tarnish resistance by eliminating microstructural inhomogeneities.     

Preliminary observations on clinical use of a base metal casting alloy

A study was conducted to develop a laboratory technique and to evaluate the clinical efficacy of a base metal casting alloy. Slight modification of recommended investing procedures is required to produce consistently well-fitting castings with the test alloy. After 12 months of clinical service, the test alloy did not differ from the control alloy in tarnish, untoward gingival response, resistance to abrasion, or tooth sensitivity.     

远缘链球菌g型对铸钛、钴铬合金、镍铬合金修复体腐蚀失泽的研究

目的:研究远缘链球菌g 型对铸钛、Co-Cr 合金、Ni-Cr 合金修复体失泽腐蚀的影响。方法:将Co-Cr 合金、Ni-Cr合金、纯钛分别铸造制备成10 mm×10 mm×1 mm板片,每组30 片。将上述3 组每组随机分空白对照组,培养基对照组、实验组各10 片。需氧环境中,将g 型远缘链球菌接种到蔗糖琼脂培养基后,将试件贴附其表面,每周转换传递一次,共10 周。0105 %戊二醛消灭细菌,清洗,2 周后用MINOLTA CR-100 型色度计观察。结果:经统计学分析可知铸钛、Co-Cr 合金、Ni-Cr 合金修复体的空白对照组与培养基对照组的L*、a*、b*值无显著差异( P > 0105) 。铸钛、Co-Cr 合金、Ni-Cr 合金修复体实验组与空白对照组、培养基对照组的L*、a*、b*值有明显差异( P < 0105) 。结论:按CIE1976 标准检测得出远缘链球菌g 型对Co-Cr 合金、Ni-Cr 合金、铸钛修复体色泽有影响,但未超出黄绿区域。     

Corrosion evaluation of gold-based dental alloys

Three commercial gold-based dental alloys and three constant-nobility ternary alloys (Au-Ag-Cu) were evaluated for corrosion using a quantitative test battery. Integration of the current density, in a de-aerated solution of 1% NaCl along the approximate potential range found in the mouth (-300 mV to +300 mV vs. SCE), yields a quantitative rank ordering of the test alloys. The results are combined with prior findings on other commercial alloys to demonstrate the interaction of nobility and microstructure. Nobility determines the overall corrosion resistance for gold-based alloys. However, because of mutual insolubility, alloying with copper induces silver segregation, resulting in a higher corrosion rate at a given nobility. Thus, microstructure has an influence on corrosion, but heat treatments are largely ineffective in altering the basic corrosion characteristics. The test techniques, in combination with tarnish evaluations, provide a quantitative battery for alloy evaluation. The results indicate the combinations of nobility, microstructure, and environment most likely to avoid corrosion difficulties.