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William A Brantley - One of the best experts on this subject based on the ideXlab platform.
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effect of different high Palladium metal ceramic Alloys on the color of opaque and dentin porcelain
Journal of Prosthetic Dentistry, 2004Co-Authors: Minos Stavridakis, Efstratios Papazoglou, William M Johnston, Med Dent, Robert R Seghi, William A BrantleyAbstract:Abstract Statement of problem The color of dental porcelain depends on the type of metal substrate. Little research has been done to document the effects of different types of high-Palladium Alloys on the color of dental porcelain. Purpose The purpose of this in vitro study was to evaluate the effects of different high-Palladium Alloys on the resulting color of dentin porcelain, as well as on that of opaque porcelain after simulated dentin and glazing firing cycles. Material and methods Three Pd-Cu-Ga Alloys, Spartan Plus (S), Liberty (B), and Freedom Plus (F), and 5 Pd-Ga Alloys, Legacy (L), IS 85 (I), Protocol (P), Legacy XT (X), and Jelenko No.1 (N), were examined. A Pd-Ag alloy, Super Star (T), was included for comparison to the high-Palladium Alloys, and the Au-Pd alloy, Olympia (O), served as the control. Six cast discs (16 × 1 mm) were prepared from each of the Alloys. Shade B1 opaque porcelain (Vita-Omega) was applied at a final thickness of 0.1 mm. After 2 opaque porcelain firing cycles, the surfaces were airborne-particle abraded, and the specimens were divided into 2 groups. In the first group, 0.9 mm of B1 dentin porcelain was applied. The other group of specimens with only opaque porcelain underwent the same dentin porcelain and glazing firing cycles. Color differences (ΔE) were determined with a colorimeter between the control and each experimental group, after the second opaque porcelain, second dentin porcelain, and glazing firing cycles. One-way analysis of variance and Dunnett's multiple range test were performed on the ΔE data (α=.05). Results After the application of dentin porcelain, the 3 Pd-Cu-Ga Alloys showed significantly different ( P P P Conclusions The Pd-Cu-Ga Alloys with only opaque porcelain, after the simulated dentin porcelain and glazing firing cycles, exhibited clinically unacceptable color differences. The application of dentin porcelain to the Pd-Cu-Ga Alloys resulted in clinically acceptable color differences. The application of dentin porcelain to the Pd-Ag alloy, after the glazing firing cycle, resulted in clinically acceptable color differences (approximately 2.8 to 3.7 ΔE CIELAB units). The Pd-Ag alloy specimens with only opaque porcelain did not exhibit significant color differences from the control group, whereas significant color differences from the control group after the dentin porcelain and glazing firing cycles were still clinically acceptable.
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potentiodynamic polarization study of the in vitro corrosion behavior of 3 high Palladium Alloys and a gold Palladium alloy in 5 media
Journal of Prosthetic Dentistry, 2002Co-Authors: Peter Monaghan, William A Brantley, William M JohnstonAbstract:Abstract Statement of Problem. Corrosion of cast alloy restorations may lead to their failure or adversely affect their biocompatibility. Although some documentation of the corrosion behavior of the high-Palladium dental Alloys exists, questions remain about their corrosion resistance and mechanisms. Purpose. This study compared the in vitro corrosion characteristics of 3 high-Palladium Alloys and 1 gold-Palladium alloy in simulated body fluid and oral environments. Material and Methods. Two Pd-Cu-Ga Alloys and 1 Pd-Ga alloy were selected; an Au-Pd alloy served as the control. The corrosion behavior for the as-cast and simulated porcelain-firing (heat-treated) conditions of each alloy (N = 5) was evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions. Heat-treated specimens of each alloy (N = 5) were also tested in N 2 -deaerated 0.09% NaCl and Fusayama solutions (pH 4). After immersion in the electrolyte for 24 hours, the open-circuit potential (OCP) was measured, and linear polarization was performed from −20 mV to +20 mV (vs. OCP) at a scanning rate of 0.125 mV/s. Cyclic polarization was performed from −300 mV to +1000 mV and back to −300 mV (vs. OCP) at a scanning rate of 1 mV/s. Data were evaluated with analysis of variance and the Ryan-Einot-Gabriel-Welsch multiple-range test (α=.05). Results. The OCP of each alloy varied with the condition (as-cast or heat-treated) and electrolyte used. Corrosion resistance was similar for the 4 Alloys tested. For cyclic polarization, all Alloys showed active-passive or spontaneous passive behavior in nearly all electrolytes. During some reverse scans, the 3 high-Palladium Alloys displayed 3 or 5 anodic peaks. No positive hysteresis was observed for any of the alloy/electrolyte combinations evaluated. Conclusion. The corrosion resistances of the 3 high-Palladium Alloys in simulated body fluid and oral environments were comparable to that of the gold-Palladium alloy. The similar corrosion resistance for the 3 high-Palladium Alloys was attributed to their high noble metal content and theorized stable structure at the submicron level. Selective corrosion of different phases and elements, surface enrichment of Palladium, and adsorption of species are possible corrosion mechanisms. The cyclic polarization results suggest that none of the 4 Alloys would be prone to pitting or crevice corrosion under in vivo conditions, but crevice conditions should nonetheless be avoided for these Alloys in the oral environment. (J Prosthet Dent 2002;87:86-93.)
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in vitro corrosion resistance of high Palladium dental casting Alloys
Dental Materials, 1999Co-Authors: S G Vermilyea, William A BrantleyAbstract:Abstract Objective: The objective of this study was to characterize the in vitro corrosion behavior of five high-Palladium dental Alloys in two media using a potentiodynamic polarization technique. Methods: Potentiodynamic cyclic polarization between −1000 and +1000 mV (SCE), 12 h open-circuit potential measurement, and linear polarization were performed on cast specimens of three Pd–Cu–Ga Alloys and two Pd–Ga Alloys in deaerated 0.09% NaCl solution and Fusayama artificial saliva at 37°C. Zero-current potential, corrosion current density, open-circuit potential, and polarization resistance were determined. The Kruskal–Wallis test and the Mann–Whitney U -test were used to analyze the numeric findings. Results: The Pd–Cu–Ga and Pd–Ga Alloys in both the as-cast and heat-treated conditions showed spontaneous passive behavior under electrochemical conditions similar to those in the oral environment. The Pd–Cu–Ga Alloys Liberty and Spartan Plus exhibited increased activity in the Fusayama artificial saliva after the porcelain-firing heat treatment, which may have arisen from internal oxidation of casting defects. Heat-treated Freedom Plus had an unstable oxide film to form on the surface during anodic polarization and may have a limited tendency for pitting corrosion in the Fusayama artificial saliva. The two heat-treated Pd–Ga Alloys remained passive in the test media. As a group, the high-Palladium Alloys exhibited satisfactory corrosion resistance. Significance: Corrosion of high-Palladium Alloys in the oral environment involves a release of ions that is related to their biocompatibility. Knowledge of the in vitro corrosion behavior of these Alloys may lead to better understanding of any biologically adverse effects in vivo.
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Effects of three soldering techniques on the strength of high-Palladium alloy solder joints
Journal of Prosthetic Dentistry, 1998Co-Authors: Marisol Chaves, Efstratios Papazoglou, Stanley G. Vermilyea, William A BrantleyAbstract:Abstract Statement of problem. Little information is available on the optimum technique for soldering high-Palladium Alloys, which have gained considerable popularity for prosthodontic applications. Purpose. The objective of this study was to compare the flexural stress at the proportional limit of four noble dental alloy specimens soldered with torch, oven, and infrared techniques. Materials and methods. The high-Palladium Alloys studied were Legacy XT (Jelenko), Freedom Plus (Jelenko), and IS 85 (Williams/Ivoclar). A gold-Palladium alloy, Olympia (Jelenko), served as the control. Thirty round bars, 18 × 3 mm, were cast from each alloy, cut in half, aligned, and joined using Olympia Pre solder (Jelenko) for the gas-oxygen torch and the infrared technique and Alboro LF solder (Jelenko) for the oven technique. Each soldered bar was subjected to three-point bending, and the maximum elastic stress or strength of the solder joint was calculated at the proportional limit. Data were analyzed by two-way ANOVA and the Ryan-Einot-Gabriel-Welsch (REGW) multiple range test at the 0.05 level of significance. Results. There was no significant difference between torch and oven-soldering, but both were significantly different from the infrared technique. ANOVA showed a significant difference between Alloys, but this difference could not be detected with the REGW test. SEM examination of the fracture surfaces revealed grooves associated with the path of crack propagation. X-ray energy-dispersive spectroscopic analysis failed to detect copper in the solders, and there were no significant changes in the solder compositions after the melting procedures. Conclusions. All three techniques can yield satisfactory solder joints in high-Palladium Alloys. These joints should be well-polished to achieve optimal strength. (J Prosthet Dent 1998;79:677-84.)
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effects of dental laboratory processing variables and in vitro testing medium on the porcelain adherence of high Palladium casting Alloys
Journal of Prosthetic Dentistry, 1998Co-Authors: Efstratios Papazoglou, William A Brantley, William M Johnston, Alan B CarrAbstract:Abstract Purpose. This study assessed the effects of dental laboratory processing variables and testing medium on porcelain adherence of representative high-Palladium Alloys. Material and methods. The processing variables were recasting two and three times, porcelain stripping with hydrofluoric acid and rebuilding, and changing the recommended oxidation procedures. The testing medium was air for these four groups and the nontreatment group. In the last group, the specimens were stored and tested in artificial saliva. The metal ceramic specimens were fractured with biaxial flexure in constant strain. The area fraction of adherent porcelain (%) was calculated with a standardized spectrometric technique. A gold-Palladium alloy served as the control. Results. Recasting without adding new alloy negatively affected some high-Palladium Alloys. Porcelain stripping did not cause a decrease in adherence of the tested Alloys. The alternate oxidation treatment reduced significantly the porcelain adherence of the Au-Pd and one Pd-Cu-Ga alloy. Storage and testing in artificial saliva did not significantly affect the porcelain adherence of the Alloys. The Au-Pd alloy exhibited the highest porcelain adherence. (J Prosthet Dent 1998;79:514-9.)
W. M. Johnston - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical impedance spectroscopy study of high-Palladium dental Alloys. Part I: Behavior at open-circuit potential*
Journal of Materials Science: Materials in Medicine, 2002Co-Authors: P. Monaghan, W. A. Brantley, W. M. JohnstonAbstract:Electrochemical impedance spectroscopy (EIS) was used to study the in vitro corrosion of three representative high-Palladium Alloys and a gold–Palladium alloy for comparison. The corrosion resistances (measured as the charge transfer resistance R _ CT from an equivalent circuit) of the high-Palladium Alloys and the gold–Palladium alloy were comparable in simulated body fluid and oral environments, and under simulated dental plaque. The great similarity in corrosion behavior for the three high-Palladium Alloys is largely attributed to their substantial Palladium content and passivity in the laboratory test media, and possibly to their similar structure at the submicron level. Differences in composition and microstructure at the micron level and greater, including the effects of heat treatment simulating the firing cycles for dental porcelain, do not have noteworthy effects on the in vitro corrosion of the three high-Palladium Alloys. Good accuracy and convenience of extracting corrosion characteristics from equivalent circuit modeling, along with the capability of providing intrinsic information about the corrosion mechanism, enable EIS to be an excellent alternative method to conventional potentiodynamic polarization for evaluating the corrosion behavior of noble dental Alloys.
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Electrochemical impedance spectroscopy study of high-Palladium dental Alloys. Part II: Behavior at active and passive potentials*
Journal of Materials Science: Materials in Medicine, 2002Co-Authors: P. Monaghan, W. A. Brantley, W. M. JohnstonAbstract:Electrochemical impedance spectroscopic (EIS) analyses were performed on three high-Palladium Alloys and a gold–Palladium alloy at active and passive potentials in five electrolytes that simulated body fluid and oral environmental conditions. All four Alloys were previously found to have excellent corrosion resistance in these in vitro environments. Before performing the EIS analyses, alloy specimens were subjected to a clinically relevant heat treatment that simulated the firing cycles for a dental porcelain. It was found that the EIS spectra varied with test potential and electrolyte. Diffusional effects, related to the dealloying and subsequent surface enrichment in Palladium of the high-Palladium Alloys, along with species adsorption and passivation, were revealed at both active and passive potentials, although these effects were more evident at the passive potentials.
O Savadogo - One of the best experts on this subject based on the ideXlab platform.
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Palladium copper Alloys as catalysts for the oxygen reduction reaction in an acidic media i correlation between the orr kinetic parameters and intrinsic physical properties of the Alloys
Journal of Electroanalytical Chemistry, 2009Co-Authors: F Foudaonana, O SavadogoAbstract:Abstract The oxygen reduction reaction (ORR) on Pd–Cu catalyst has been studied in acidic media. The Palladium Alloys were prepared by coating glassy (GC) carbon substrates using a R-F magnetron sputtering equipment with a Palladium and a copper wafer as targets. The dual sputtering we used has allowed us to obtain a thin film of 1 μm thick. The ORR kinetics was studied on these catalysts in 0.1 M HClO4. Cyclic voltammetry (CV) was used to determine the electrochemical surface area (Sel). An increase in Sel with the Cu content in the alloy was observed for the Alloys containing less than 50% in Cu while a constant value of 23 cm2 is reached after this content in Cu. It was further shown that the ORR on the Pd–Cu Alloys proceeds through four transferred electrons mechanism and a Tafel slope of 60 mV/dec at low over potentials. The Pd50Cu50 exhibits the highest activity for this reaction. The enhancement of the electro catalytic activity is attributed to an optimal d band property that makes easier the OOH dissociative adsorption which is considered as chemical rate determining step (RDS) for the ORR.
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new Palladium Alloys catalyst for the oxygen reduction reaction in an acid medium
Electrochemistry Communications, 2004Co-Authors: O Savadogo, K Oishi, Shigenori Mitsushima, Nobuyuki KamiyaAbstract:Extremely active Palladium-based Alloys catalysts without platinum for the oxygen reduction reaction (ORR) in an acid medium were shown for the first time. The Palladium Alloys were prepared by sputtering under a vacuum of less than 10−4 Pa from a Palladium target and an alloying metal sheets on a glassy carbon support. Their electrochemical characteristics for ORR were determined at 30 °C in sulphuric acid. It was demonstrated that the base voltammograms (CVs) of Pd–Co Alloys did not show significant change in the shape or size during the whole measurements procedure. Furthermore the Pd–Co alloy CV were found to be completely different from those of Pd and Co alone and they never changed to become more Pd-like or Co-like. The Pd–Co alloy catalysts are stable under the applied experimental conditions. The interesting properties of the Alloys for the ORR were attributed to an appropriate electronic stabilisation of the alloying element atom in the alloy which may prevent its corrosion and which allows the enhancement of its catalytic activity. It was further demonstrated that an improvement of at least 250 mV, based only on a theoretical estimation from Tafel slope, in ORR over-voltage could be obtained if a Pd–Co 28% catalyst is used at 30 °C instead of Pt for PEFC or acid Solid Polymer Electrolyser Applications.
W. A. Brantley - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical impedance spectroscopy study of high-Palladium dental Alloys. Part II: Behavior at active and passive potentials*
Journal of Materials Science: Materials in Medicine, 2002Co-Authors: P. Monaghan, W. A. Brantley, W. M. JohnstonAbstract:Electrochemical impedance spectroscopic (EIS) analyses were performed on three high-Palladium Alloys and a gold–Palladium alloy at active and passive potentials in five electrolytes that simulated body fluid and oral environmental conditions. All four Alloys were previously found to have excellent corrosion resistance in these in vitro environments. Before performing the EIS analyses, alloy specimens were subjected to a clinically relevant heat treatment that simulated the firing cycles for a dental porcelain. It was found that the EIS spectra varied with test potential and electrolyte. Diffusional effects, related to the dealloying and subsequent surface enrichment in Palladium of the high-Palladium Alloys, along with species adsorption and passivation, were revealed at both active and passive potentials, although these effects were more evident at the passive potentials.
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Electrochemical impedance spectroscopy study of high-Palladium dental Alloys. Part I: Behavior at open-circuit potential*
Journal of Materials Science: Materials in Medicine, 2002Co-Authors: P. Monaghan, W. A. Brantley, W. M. JohnstonAbstract:Electrochemical impedance spectroscopy (EIS) was used to study the in vitro corrosion of three representative high-Palladium Alloys and a gold–Palladium alloy for comparison. The corrosion resistances (measured as the charge transfer resistance R _ CT from an equivalent circuit) of the high-Palladium Alloys and the gold–Palladium alloy were comparable in simulated body fluid and oral environments, and under simulated dental plaque. The great similarity in corrosion behavior for the three high-Palladium Alloys is largely attributed to their substantial Palladium content and passivity in the laboratory test media, and possibly to their similar structure at the submicron level. Differences in composition and microstructure at the micron level and greater, including the effects of heat treatment simulating the firing cycles for dental porcelain, do not have noteworthy effects on the in vitro corrosion of the three high-Palladium Alloys. Good accuracy and convenience of extracting corrosion characteristics from equivalent circuit modeling, along with the capability of providing intrinsic information about the corrosion mechanism, enable EIS to be an excellent alternative method to conventional potentiodynamic polarization for evaluating the corrosion behavior of noble dental Alloys.
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Comparison of mechanical properties for equiaxed fine-grained and dendritic high-Palladium Alloys
Journal of Materials Science: Materials in Medicine, 2000Co-Authors: E. Papazoglou, Q. Wu, W. A. Brantley, J. C. Mitchell, G. MeyrickAbstract:Two Pd-Cu-Ga Alloys and a Pd-Ga alloy were selected for study. Bars of each alloy were tested in tension for the as-cast and simulated porcelain-firing conditions, and values of mechanical properties were measured. Fracture surfaces and microstructures of axially sectioned fracture specimens were observed with the SEM. The two Pd-Cu-Ga Alloys exhibited similar mechanical properties. The Pd-Ga alloy had lower strength and higher percentage elongation. Heat treatment simulating porcelain firing cycles decreased the strength of both Pd-Cu-Ga Alloys and increased their ductility. However, this heat treatment did not significantly affect the mechanical properties of the Pd-Ga alloy. All three high-Palladium Alloys had the same modulus of elasticity. The amount of overall porosity was relatively minimal (< 1%) and not significantly different among the three Alloys. However, porosity was a significant factor for UTS of one Pd-Cu-Ga alloy and the Pd-Ga alloy.
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new high Palladium casting Alloys 1 overview and initial studies
International Journal of Prosthodontics, 1991Co-Authors: A B Carr, W. A. BrantleyAbstract:High-Palladium Alloys for metal ceramic restorations, based on the Pd-Cu-Ga and Pd-Ga systems, were introduced to the dental profession during the past decade. These Alloys have become increasingly popular because they are much less expensive than the gold-based Alloys, and recently marketed high-Palladium alloy compositions have excellent mechanical properties. A summary of the important melting and casting considerations for these somewhat technique-sensitive Alloys is presented together with an overview of important dental materials science aspects and the results of a dental laboratory survey. A maxillary central incisor coping was chosen as the clinically appropriate specimen shape, and the gas-oxygen torch melting technique was found to produce castings with clinically acceptable levels of marginal sharpness and little evidence of microporosity. The etched as-cast high-Palladium Alloys exhibited fine-scale multiphase microstructures, and a noteworthy finding was that relative proportions of the microstructural constituents frequently varied for thin versus thick sections of the cast specimens.
P. Monaghan - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical impedance spectroscopy study of high-Palladium dental Alloys. Part I: Behavior at open-circuit potential*
Journal of Materials Science: Materials in Medicine, 2002Co-Authors: P. Monaghan, W. A. Brantley, W. M. JohnstonAbstract:Electrochemical impedance spectroscopy (EIS) was used to study the in vitro corrosion of three representative high-Palladium Alloys and a gold–Palladium alloy for comparison. The corrosion resistances (measured as the charge transfer resistance R _ CT from an equivalent circuit) of the high-Palladium Alloys and the gold–Palladium alloy were comparable in simulated body fluid and oral environments, and under simulated dental plaque. The great similarity in corrosion behavior for the three high-Palladium Alloys is largely attributed to their substantial Palladium content and passivity in the laboratory test media, and possibly to their similar structure at the submicron level. Differences in composition and microstructure at the micron level and greater, including the effects of heat treatment simulating the firing cycles for dental porcelain, do not have noteworthy effects on the in vitro corrosion of the three high-Palladium Alloys. Good accuracy and convenience of extracting corrosion characteristics from equivalent circuit modeling, along with the capability of providing intrinsic information about the corrosion mechanism, enable EIS to be an excellent alternative method to conventional potentiodynamic polarization for evaluating the corrosion behavior of noble dental Alloys.
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Electrochemical impedance spectroscopy study of high-Palladium dental Alloys. Part II: Behavior at active and passive potentials*
Journal of Materials Science: Materials in Medicine, 2002Co-Authors: P. Monaghan, W. A. Brantley, W. M. JohnstonAbstract:Electrochemical impedance spectroscopic (EIS) analyses were performed on three high-Palladium Alloys and a gold–Palladium alloy at active and passive potentials in five electrolytes that simulated body fluid and oral environmental conditions. All four Alloys were previously found to have excellent corrosion resistance in these in vitro environments. Before performing the EIS analyses, alloy specimens were subjected to a clinically relevant heat treatment that simulated the firing cycles for a dental porcelain. It was found that the EIS spectra varied with test potential and electrolyte. Diffusional effects, related to the dealloying and subsequent surface enrichment in Palladium of the high-Palladium Alloys, along with species adsorption and passivation, were revealed at both active and passive potentials, although these effects were more evident at the passive potentials.