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PubMed1997

Soldering strength of post-soldering of palladium-based metal-ceramic alloys.

To evaluate the post soldering of metal-ceramic alloys that have palladium as their main component, palladium-based metal-ceramic alloys with different compositions were used to assess soldering strength. Four palladium-based metal ceramic alloys were selected: Pd-Cu system, Pd-Ag system, Pd-Ni system, and Pd-Sb system, and gold-silver-palladium alloy was also used. As soldering materials, 12 k gold solder and 16 k gold solder were used. After post-soldering by butt joint samples that had been heat treated (equivalent to the porcelain firing cycle), soldering strength was evaluated by measuring the flexural strength. The yield strength had a range of 300 to 800 MPa, and the ultimate strength was in the range of 350 to 1,000 MPa; the Pd-Ag type showed the highest value. There was no correlation between the yield strength of the metal-ceramic alloys and that of the soldering samples. When the soldering strength of 12 k gold solder and 16 k solder were compared, the samples soldered with 12 k gold solder showed higher values in all cases. Samples in which heating was prolonged for 10 seconds had a high strength, within 100 to 500 MPa in yield strength and 100 to 800 MPa in ultimate strength.

Analysis of Variance↗
PubMed1994

Evaluation of soldered connectors of two base metal ceramic alloys.

Soldered connectors for two base metal ceramic alloys (nickel-chromium and cobalt-chromium) were compared by use of four different techniques: (1) infrared preceramic soldering, (2) gas and oxygen preceramic soldering, (3) porcelain furnace postsoldering under vacuum, and (4) porcelain furnace postsoldering without vacuum. A control group was established with solid cast specimens of each alloy. No statistically significant difference was noted between infrared and torch preceramic soldering techniques for either of the two alloys. However, the joints postsoldered under vacuum were significantly superior to postsoldered connectors without vacuum (p < 0.0001). No significant differences were observed among techniques 1, 2, and 3, although the three groups were substantially superior to technique 4 for both alloys (p = 0.05). The control group for both alloys was appreciably stronger than the soldered groups (p < 0.0001), and the nickel-chromium samples within the control group were significantly stronger than the Co-Cr samples.

Analysis of Variance↗
PubMedDate not supplied

Comparative evaluation of the effect of simulated porcelain firing cycle on the mechanical properties and microstructure of base metal ceramic alloys.

A comparison of mechanical properties and microstructure of four metal ceramic alloys in as-cast and heat-treated conditions resulted in significant differences. The alloys that were tested included two nickel-based and two cobalt-based metal ceramic alloys. Mechanical properties tested included strength, percent elongation and hardness. Ten tensile bars were cast for each alloy. Five of the ten bars for each alloy were randomly selected for heat treatment with the simulated porcelain firing cycle. Results indicated that the nickel-based alloys were weakened by the heat treatment and showed a decreased hardness and an increased elongation. The effects of heat treatment on the strength of cobalt-based alloys were variable, showing an increase in hardness and a decrease in elongation. Differences in mechanical properties exhibited by the alloys were related to compositional and microstructural changes.

Analysis of Variance↗
PubMed1997

Corrosion resistance of the soldering joint of post-soldering of palladium-based metal-ceramic alloys.

To evaluate the corrosion resistance of post soldering of metal-ceramic alloys, four commercially available palladium-system metal-ceramic alloys (Pd-Cu, Pd-Ni, Pd-Ag, and Pd-Sb systems) and two types of solder (12 k gold solder and 16 k gold solder) with different compositions and melting points were used. The corrosion resistance of the soldered joint was evaluated by anodic polarization. The electrochemical characteristics of soldered surface were measured using electrochemical equipment. Declines in corrosion resistance were not detectable with Pd-Cu, Pd-Ag and Pd-Sb types, but break down at low potential occurred with Pd-Ni type.

Corrosion↗
PubMed1991

Effect of different metal ceramic alloys on the color of opaque and dentin porcelain.

Certain metal ceramic alloys alter the final color of bonded porcelain. Contradicting results, inconsistent test designs, and incomplete alloy selections have led to some confusion. In this study, differential colorimetric analysis was done at the opaque and dentin porcelain stages with five major types of metal ceramic alloys. The color stability of the porcelain on the high-noble metal alloys was found to be excellent. The palladium-silver and nickel-chromium alloys resulted in significant color changes of the dentin porcelain only. The greatest changes in color were found with the palladium-silver alloy, which resulted in a higher yellow-green saturation. The nickel-chromium alloy also produced a color change, although not as severe, resulting in a porcelain shade with a reduced Value or lightness.

Chromium Alloys↗
PubMed2001

Effect of pH on endotoxin affinity for metal-ceramic alloys.

STATEMENT OF PROBLEM: Crevicular pH may modify bacterial endotoxin affinity for high-noble metal-ceramic alloys. PURPOSE: Porphyromonas gingivalis lipopolysaccharide (LPS) affinity for 3 metal-ceramic alloys at 3 different pH levels was compared in vitro by measuring adsorption to and release from the alloy surface. MATERIAL AND METHODS: Metallographically polished disks were fabricated from Pd-Ag-Sn, Au-Pd-Ag-Sn-In, and Au-Pd-In-Ga alloys. Clean disks were placed individually into 1 mL at pH 6.5, 7.0, or 7.5 phosphate-buffered saline solution containing 0.9 endotoxin units per square millimeter tritiated LPS (n = 3 disks per alloy-pH group). The disks were incubated for 24 hours at 37 degrees C before being transferred to LPS-free buffer and incubated, again for 24 hours at 37 degrees C, to evaluate elution. This transfer continued at 24-hour intervals up to 96 hours total elution incubation. Lipopolysaccharide adsorption to and elution from disks was determined through liquid scintillation spectrometry. Adsorption data were evaluated with a 2-way analysis of variance (alpha=.05) and the post hoc Tukey honestly significant difference test. RESULTS: Lipopolysaccharide adsorption values ranged from 0.48 +/- 0.04 EU/mm(2) for the Au-Pd-Ag-Sn-In alloy at pH 7.5 to 0.75 +/- 0.04 EU/mm(2) for the Pd-Ag-Sn alloy at pH 6.5. Alloy type (P=.0001) and environmental pH (P=.0001) significantly influenced adsorption. Adsorption to the Pd-Ag-Sn and Au-Pd-In-Ga alloys at pH 6.5, 7.0, and 7.5 were similar and decreased with increasing pH. In contrast, adsorption to the Au-Pd-Ag-Sn-In alloy was significantly less than to other alloys at pH 6.5 but did not differ at other pH levels. Lipopolysaccharide release from the alloy surface could not be detected. CONCLUSION: P. gingivalis LPS affinity for metal-ceramic alloys was modified by environmental pH. The degree of LPS adsorption depended on the composition and surface chemistry of each alloy.

Adsorption↗
PubMed1990

Properties of cobalt-chromium metal ceramic alloys after heat treatment.

A comparison of mechanical properties of seven metal ceramic alloys in as-cast and heat-treated conditions resulted in significant differences. The alloys that were tested included seven cobalt-chromium metal ceramic alloys. Mechanical properties include strength, elongation, modulus of elasticity, and microhardness. Twenty-four tensile bars were cast for each alloy. Twelve of the 24 bars for each alloy were randomly selected for heat treatment with the Ceramco technique. Results indicated that the tested alloys had similar mechanical property values as a group in both the as-cast and the heat-treated conditions. The heat treatment had little effect on the cobalt-chromium alloys, although several did become significantly harder. In either condition, the cobalt-chromium alloys showed a high value of strength, a low percent of elongation, a high modulus of elasticity, and a high value of hardness. The high value of hardness and the low percent of elongation would make these alloys difficult to handle clinically.

Analysis of Variance↗
PubMedDate not supplied

The evaluation of factors affecting the castability of metal ceramic alloy--investment combinations.

An evaluation of the castability of metal ceramic alloy-investment combinations using a mesh test and utilizing a factorial design concept has shown that different metal ceramic alloys (gold-based, palladium-based, and nickel-chromium-based alloys) react differently, as far as castability is concerned, to various factors involved in the casting process. These factors were divided into two groups: procedural factors, that included sprue diameter, investing technique, and melting and casting method; and operator factors, which included alloy casting temperature, mould temperature, and heat-soak times. Each of these factors had two or three levels.

Chromium Alloys↗
PubMed2005

Static immersion and irritation tests of dental metal-ceramic alloys.

The expansion of the European Union is bringing new types of metal-ceramic alloys to the market, i.e. alloys probably unknown in Western-European dentistry. The aim of this study was to investigate recent developments and "classic" alloy compositions (one iron and two cobalt alloys, unalloyed titanium and an experimental titanium-zirconium alloy, and one gold alloy containing copper and zinc). The alloys and titanium were subject to static immersion in a 0.1 mol l(-1) solution of saline lactic acid before and after oxidation, hence simulating the temperature cycles for the application of ceramic to metal. The greatest amounts of released metal ions were found in the electrolytes of the oxidized gold alloy and of a cobalt alloy not exposed to high-temperature oxidation. Corrosion of the titanium and alloy surfaces was related to the condition of the specimen. The irritation potentials of some metal ions found in the electrolyte were investigated by performing the hen's egg test-chorio-allantoic membrane (HET-CAM) procedure with 1 mmol l(-1) solutions of Ce(3+), Co(2+), Cu(2+), Zn(2+), Fe(2+), and Ti(4+) ions. The irritation potential of the electrolyte of the oxidized gold alloy with a high concentration of metal elements was also investigated. Of these solutions, only the 1 mmol l(-1) Cu(2+) solution was graded as slightly irritating.

Animals↗
PubMed2006

[Effect of porcelain firing cycle on microstructure and corrosion resistance of 4 metal ceramic alloys].

OBJECTIVE: To determine the effect of porcelain firing cycle on microstructure of 4 metal ceramic alloys, and to analyze the changes of their corrosion resistance in the artificial saliva. METHODS: We simulated the process of firing and repolishing when fabricating porcelain-fused-to-metal restoration in clinic,and then observed the microstructures of Ni-Cr, Ni-Cr-Ti, Co-Cr alloys and high gold alloy by field emission scanning electron microscopy and energy dispersive spectroscopy. The electrochemical corrosion behavior of alloys in artificial saliva was analyzed by polarization curves and corrview 2 corrosion analysis software. The data of self-corrosion potential and transpassive potential were obtained and analyzed. RESULTS: After the porcelain firing cycle, the surface composition changed slightly, and the morphological in the 3 predominate base metal alloys also changed. The self-corrosion potential turned to more negative, and the transpassive potential declined. CONCLUSION: The procedure of porcelain firing cycle can affect the surface microstructure and increase the corrosion of 4 metal-ceramic alloys.

Corrosion↗
PubMed1989

Veterans Administration Cooperative Studies Project No. 147. Part IX: A comparison of the mechanical properties of several alternative metal ceramic alloys cast in clinical and research laboratories.

Comparison of mechanical properties of five metal ceramic alloys cast in clinical and research laboratories resulted in significant differences. Tested alloys included one Au-Pd (control), one Pd-Ag, and three Ni-Cr. Mechanical properties included strength, elongation, and microhardness. Tensile bars were torch cast simultaneously with restorations in the clinical laboratory and induction cast by using a preformed design in the research laboratory. Mechanical properties of most alloys showed larger variations when cast in the clinical laboratory. In the clinical laboratory the Au-Pd alloy showed significantly higher values for all properties. One Ni-Cr alloy was not significantly affected by environment for all properties. The remaining alloys were significantly affected for some properties by environment. The different laboratories had no greater or lesser effect on the base metals as a group than on the noble metals. Variation in handling, spruing, casting, and specimen size may account for some of the differences between laboratories.

Ceramics↗
PubMed1990

Veterans Administration Cooperative Studies Project No. 147: association of metallic taste with metal ceramic alloys.

We examined patients to find out whether they noticed the prevalence of metallic taste and set out to determine the association of metallic taste with demographic, medical, and dental factors. Data were collected as part of a Veterans Administration Cooperative Study investigating the suitability of alternative metal ceramic alloys as substitutes for alloys that contain gold. Crowns and fixed partial dentures were made from control and alternative alloys for accepted volunteer patients. A month after placement of the restorations and at regularly scheduled recall appointments, the patients were asked if they tasted a metallic flavor. Of the 2023 times the question was asked, 101 positive responses were given by 68 patients (46 reported metallic flavor once, and 22 reported it more than once). Results indicated that youth, sensitivity to heat and cold, bruxism, grinding, and an increasing number of restorative units were significantly related to metallic taste. For any given visit, about 5% of the patients reported tasting a metallic flavor regardless of the type of alloy that was used in the restoration. Metallic taste does not appear to be a problem with alternative alloys.

Adult↗
PubMed1989

Veterans Administration Cooperative Studies Project No. 147/242. Part VII: The mechanical properties of metal ceramic alloys as cast and after simulated porcelain firing.

Comparison of mechanical properties of seven metal ceramic alloys in as-cast and heat-treated conditions resulted in significant differences. Tested alloys included one Au-Pd (control), three palladium-based, and three nickel-based alloys. Mechanical properties included strength, elongation, modulus, and microhardness. Twenty-four tensile bars were cast for each alloy. Twelve of the 24 bars for each alloy were randomly selected for heat treatment by the Ceramco technique. After heat treatment the Au-Pd alloy became stronger and harder and showed an increased elongation. The effects of heat treatment on the strength of the palladium-based alloys were variable, showing a decrease in hardness and an increase in elongation. The nickel-based alloys were weakened by the heat treatment and showed a decrease in hardness and an increase in elongation. Heat treatment did not significantly affect the modulus of any of the tested alloys.

Chemical Phenomena↗
PubMed1980

[The influence of surface treatments on non-precious metal-ceramics alloys (author's transl)].

In this study, the author attempted to find out the suitable methods of surface treatments for non-precious metal-ceramics alloys. Three Ni-Cr system alloys in the market, (Gemini II, Euro-ceram and Wiron S) were used. The shear bond strength was measured under the various conditions, varying the heating temperatures of pre-oxidation treatment and finishing methods of the metal surface. A specially designed apparatus which had been improved by the author, was used to measure the shear bod strength of the metal-ceramics. The following results were obtained. 1. The testing method improved was found better as a means of measuring the bond strength. Because the shear bond strength which was obtained by this testing method was hardly affected by the compressive force originating from porcelain contraction or the strength of alloys. 2. In the case of Gemini II and Euro-ceram, the influence of the finishing treatment on the properties was great. The coarser the surface roughness, the greater the value of the shear bond strength. 3. In the case of Wiron S, the influence of the pre-oxidation treatment was great. The higher the temperature of treatment, the greater the value of shear bond strength. 4. The optimum surface treatment of metal was obtained among three alloys respectively. The shear bond strength of Gemini II was greater than the others under any condition. In the case of Euro-ceram, the highest bond strength was obtained under the coarser surface condition regardless of the temperature of pre-oxidation treatment. In the case of Wiron S, the highest bond strength was obtained by the surface which was finished by the #600 emerypaper and the higher temperature of pre-oxidation treatment.

Chromium↗
PubMedDate not supplied

Detecting silver-containing metal ceramic alloys that discolor porcelain.

Dental laboratories need an internal method to detect silver-containing metal ceramic alloys that stain porcelain. A fiberoptic colorimeter, calculations, and data describe Ag-vapor staining in standard CIE (1976) L*a*b* color space. The color difference value (CDV) of delta L*, delta a*, delta b*, and delta E* for porcelain before and after firing with Pd-Ag alloy, Au-Pt-Pd alloy, and control groups were calculated from L*, a*, and b* values. The CDV for all groups showed a more translucent (-delta L*) porcelain after the second firing. The CDV of porcelain disks exposed to Pd-Ag alloy showed an intense yellow (+ delta b*) stain with slight "greening" (-delta a*). The disks exposed to the Au-Pt-Pd group showed a slight yellow (-delta b*) stain. The delta b* values for the Pd-Ag group were significantly different from the other groups. This color shift (+ delta b) was clearly observed with the unaided eye.

Colorimetry↗
PubMed2005

[Effects of varying the opaque thickness and the type of metal ceramic alloy on color].

OBJECTIVE: To compare the color differences of different metal bases and different opaque thickness, and evaluate the best thickness of opaque on different metal bases. METHODS: Precious metal, gold sediment and Ni-Cr plates were prepared as bases, then opaque samples of 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5 mm thickness were fabricated on such plates. Minolta chromatics meter CR-321 was used to examine the color properties of these samples, and deltaE was calculated to evaluate the color difference of the specimens. RESULTS: For the restoration based on Ni-Cr and precious alloys, the color of restorations was not affected by the color of metal bases as the thickness of opaque reached 0.3 mm, and the chromatic value deltaE < 1.5 NBS. For the restoration based on gold sediment, the color of restoration was not affected by the color of metal as the thickness of opaque reached 0.1 mm, and the chromatic value deltaE < 1.5 NBS. CONCLUSION: Different opaque thickness was necessary to obtain ideal color appearance in clinic. As the opaque thickness increased, the color of restoration based on Ni-Cr and noble metal increased but the color of restoration based on gold sediment decreased.

Color↗
PubMed1995

A comparison of infrared- and torch-soldering of Au-Pd and Co-Cr metal-ceramic alloys using a high-fusing solder.

PURPOSE: The purpose of this study was to compare the bond strengths and fracture modes of soldered joints formed by infrared and gas-oxygen torch heating of a high-fusing, gold-based solder in two metal-ceramic alloys. MATERIALS AND METHODS: Pairs of half-dumbbell-shaped specimens of either an Au-Pd or a Co-Cr alloy were positioned with a 0.25-mm gap and were joined using a high-fusing, gold-based solder by either gas-oxygen torch heating or infrared heating. The resulting specimens were subjected to a heat treatment that simulated ceramic firing. Each specimen was fractured in tension at a loading rate of 0.5 cm/min, and its bond strength was measured. The halves of the specimen were rejoined using the other heating method and were heat treated, and the specimen's bond strength was again measured. Fractured cross-sections were examined at a magnification of 40x to determine the following: the fracture mode (adhesive, cohesive, or mixed); the percentage of adhesive fracture; the presence or absence of voids, porosities, or flux inclusions; and the percentage of the cross-section that was discolored. RESULTS: Three-factor analyses of variance showed that neither the heating method, the particular specimen tested, nor the order of testing significantly affected the bond strength (P < .05). For each alloy, significantly fewer infrared-heated joints than torch-heated joints contained voids, porosities, or flux inclusions visible at 40x (chi 2 test, P < .05). All fractures were either entirely cohesive in the solder or mixed cohesive and adhesive. When infrared heating was used, entirely cohesive fractures occurred more frequently in the Au-Pd alloy specimens than in the Co-Cr alloy specimens (chi 2 test, P < .05). The coefficients of variation of the bond strengths for the infrared-heated joints were smaller than those for the torch-heated joints. CONCLUSIONS: Although the two heating methods produced solder joints that had strengths that were not significantly different, infrared-heated joints showed less scatter in bond strengths. It was suggested that, in the hands of most technicians, fewer infrared-heated joints would contain defects visible at a magnification of 40x. The presence of such defects may increase the probability of in vivo failure caused by cyclic stresses.

Analysis of Variance↗