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At least 19 recordsLinked to original sources
PubMed1989

[Fatigue properties of dental alloys. 12% Au-Pd-Ag alloy and type III gold alloy].

Usually the mechanical properties of dental alloys are determined from the values obtained through static tests of their tensile strength, hardness, etc. Generally, high tensile strength and ductility are preferred. However, when small stresses within proportional limits are applied repeatedly (even though not amounting to destructive forces in static tests), they may cause rupture in the alloy or, at least, cause it to lose its original mechanical properties. This phenomenon is called metal fatigue. It is estimated that the intraoral stress loads received by dental restorations during mastication or during insertion and removal of appliances are repeated more than 3 x 10(5) times/year. From this standpoint, it may be more appropriate to estimate the fracture strength of such dental alloys based on the fatigue properties of the restorative materials used for clasps, bars, and fixed bridges. For this reason, it is necessary to obtain data through fatigue tests on the fatigue strength and the fatigue endurance limits of dental alloys, and it is important to find a correlation between these data and the static data on tensile strengths and ductility obtained by tensile tests. Two alloys are used in these experiments. Both wrought specimens and cast specimens of 12% Au-Pd-Ag and Type III gold alloy were prepared for the fatigue tests. The size of the rectangular wrought specimens was 3 x 4 x 110 mm. The 12% Au-Pd-Ag alloy was heated to 800 degrees C for 15 minutes, quenched, and reheated to 400 degrees C for 20 minutes and quenched again according to the manufacturer's instructions for heat treatment. The Type III gold alloy was heated to 700 degrees C for 10 minutes, quenched, and reheated to 350 degrees C for 20 minutes and quenched again. The cylindrical cast specimens were 60 mm long and 2 mm in diameter. They were invested by conventional methods and cast in a centrifugal casting machine, Thermotrol Model 2500. The four point bending test for the wrought specimen was performed with a Universal Fatigue testing machine, Shimazu UF-15 at a stress amplitude rate of 30 Hz. The cylindrical cast specimens were tested in cyclic tension in a Hydraulic IC Servo Machine, Instron Model 8501 at a gauge length of 25 mm and a stress amplitude of 10 Hz. The tensile tests for both wrought and cast specimens were performed with a Universal Testing Machine, Instron Model 1125 and measured at a cross-head speed of 1 mm/min.(ABSTRACT TRUNCATED AT 400 WORDS)

Elasticity↗
PubMed1976

[Studies on high temperature oxidation of noble metal alloys for dental use. (III) On high temperature oxidation resistance of noble metal alloys by adding small amounts of alloying elements. (author's transl)].

The previous report pointed out the undesirable effects of high temperature oxidation on the casting. The influence of small separate additions of Zn, Mg, Si, Be and Al on the high temperature oxidation of the noble metal alloys was examined. These alloying elements were chosen because their oxide have a high electrical resistivity and they have much higher affinity for oxygen than Cu. The casting were oxidized at 700 degrees C for 1 hour in air. The results obtained were as follows: 1. The Cu oxides are not observed on the as-cast surface of noble metal alloys containing small amounts of Zn, Mg, Si, Be, and Al. The castings have gold- or silver-colored surface. 2. After heating of the unpolished and polished castings, the additions of Si, Be and Al are effective in preventing oxidation of Cu in the 18 carats gold alloys. Especially the golden surface is obtained by adding Be and Al. But there is no oxidation-resistance on the polished castings in the alloys containing Zn and Mg. 3. The zinc oxide film formed on the as-cast specimen is effective in preventing of oxidation Cu in 18 carats gold alloys. 4. It seems that the addition of Al is most available in dental application.

Aluminum↗
PubMed2002

Potentiodynamic polarization study of the in vitro corrosion behavior of 3 high-palladium alloys and a gold-palladium alloy in 5 media.

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 (alpha=.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.

Adsorption↗
PubMed1999

Infrared gold alloy brazing on titanium and Ti-6Al-4V alloy surfaces and its application to removable prosthodontics.

PURPOSE: This study investigated the area size of the flow of a gold braze alloy on commercially pure titanium and Ti-6Al-4V alloy plates, and elemental composition at the interface was determined. In the second part of this study, the tensile strengths of titanium plates brazed using a gold alloy were investigated. MATERIALS AND METHODS: Chips of Type IV gold alloy and silver braze alloys were melted onto commercially pure titanium and Ti-6Al-4V surfaces in a dental infrared radiation unit. Flow area of each braze alloy was measured using a digital image analyzer. Tensile specimens (n = 5) were also prepared by infrared brazing using the braze alloys. Five specimens for each combination of the two titanium plates and the two braze alloys were subjected to tensile loading using a Universal testing machine. Electronprobe microanalysis of x-rays at cross-section of the brazed joints to determine elemental composition across the interface, as well as scanning electron microscopic observation at the fracture surfaces, were also conducted. RESULTS: The braze alloys flowed well and spread over the Ti and Ti-6Al-4V plates. Braze alloy type significantly influenced flow, and the gold alloy flowed less on the titanium materials. The mean tensile strengths of Ti and Ti-6Al-4V plates brazed using the gold braze alloy were 219 MPa and 417 MPa, respectively. The fracture surfaces of Ti-6Al-4V specimens with the gold braze alloy exhibited typical ductile behavior. Ti with the same braze alloy showed brittle surfaces. A greater concentration of Cu was found at the Ti with gold braze interface. CONCLUSION: The flow and the tensile strength of the gold alloy coating on titanium surface by means of an infrared brazing is adequate for dental use.

Alloys↗
PubMed1989

[A basic study on gallium alloys for dental restorations. Improvement of liquid gallium alloy].

This study was made to compare the physical and chemical properties of amalgam with those of gallium alloy in which the invented liquid alloy containing the three fundamental components of Ga-Sn-In or Ga-Sn-In-Ag were used instead of mercury. Experiment 1. The physical and chemical properties were investigated after the liquid gallium alloy and high copper amalgam powder were mixed. The following results were obtained; 1) The invented gallium alloy group showed expansion in dimensional changes immediately after mixing. This alloy group showed the same compressive and diametral tensile strength as those in amalgam after 7 days. 2) This alloy group showed slightly more corrosion weight loss in 0.05% HCl and 1% lactic acid solutions than that in amalgam, but this alloy group showed the same corrosion weight loss in 1% NaCl solution and artificial saliva as in amalgam. Also this alloy group showed more discoloration (delta E, NBS) in 0.1% Na2S solution than that in amalgam, but this showed the same degree of discoloration in artificial saliva. Experiment 2. The physical and chemical properties were investigated after the same liquid gallium alloy and Ag-Pd-Sn-Cu-Zn alloy powder were mixed. The following results were obtained; 1) The invented gallium alloy group showed expansion in dimensional changes immediately after mixing. This showed superior quality in compressive and diametral tensile strength as compared with those of amalgam. 2) The invented gallium alloy showed slightly more corrosion weight loss in 0.05% HCl and 1% lactic acid solutions than that in amalgam, but this alloy group showed the same corrosion weight loss in 1% NaCl solution and artificial saliva as in amalgam. Also this alloy group showed more discoloration (delta E, NBS) in 0.1% solution than that in amalgam, but it was the same in artificial saliva.

Dental Alloys↗
PubMed2000

Cytotoxicity of nickel-chromium alloys: bulk alloys compared to multiple ion salt solutions.

OBJECTIVE: Nickel-based alloys have been in use since the 1930s; however, there are concerns regarding the biocompatibility of the metallic ions released from these alloys to surrounding tissues. The objective of this study was to better understand nickel-based alloy cytotoxicity as well as determine if multiple ion salt solutions can be used to model the cytotoxic effects of bulk implant alloys. METHODS: This study evaluated cellular morphology, viability, membrane integrity, and alterations in metabolic activity, including DNA synthesis, RNA synthesis, protein synthesis, oxygen consumption, intracellular ATP levels, and glucose-6-phosphate dehydrogenase in response to bulk alloys and multiple ion salt solutions. RESULTS: Over a 24- or 72-h exposure time, the nickel-based alloys released a total ion concentration in the parts per billion range and caused alterations in DNA, RNA, and protein synthesis, intracellular ATP levels, and glucose-6-phosphate dehydrogenase activity. Interestingly, cellular responses to the salt solutions representing the ions released from the alloys were not consistently significantly similar to those elicited from the alloys. SIGNIFICANCE: From these studies, it was shown that a number of cellular functions are altered in response to ions released from these implant alloys. However, cellular functions were not similarly altered in response to salt solutions representing the ions released from the alloys. These results demonstrated salt solutions cannot be easily used to represent alloy cytotoxicity, and ionic release from alloys is a complex process dependent on variables including ion chemistry, ion valence, and dose-time dependence. This study provides a better understanding of the metabolic response of fibroblasts to ions released from dental alloys; and is a good first step towards developing a more reliable cell culture model of cytotoxicity.

Adenosine Triphosphate↗
PubMed1989

[Composition and morphology of oxides on porcelain fused to Ni-Cr alloys. Be containing alloys].

Bonding strength between porcelain and Ni-Cr alloy for the porcelain fused-to metal crown in which Be is contained in the alloy is known to be higher than those in which Be is not contained. Since, bonding between porcelain and alloy is the reaction of oxides and porcelain, the bonding is thought to be influenced by the quality the oxides film which forms on the alloy surface. The purpose of this study was to determine the composition and morphology of the oxides formed on both Be containing and non-Be contained Ni-Cr alloys. The oxides analysis was done using an EPMA and Auger analysis. Also, the Porcelain/Ni-Cr alloy interface was observed by a scanning electron microscope (SEM). The following results are indicated from this investigation: 1. The oxides from the alloys not containing Be are corundum type Cr2O3 and spinel type NiCr2O4. These oxide layers are uniform, thick and porous and the adhesion to alloy is poor. 2. The oxides from alloy containing Be is BeO only. The BeO is uniform, thin and condensed. The adhesion to the alloy is good. 3. The oxide layer formed when the porcelain is fused to alloy containing Be is thin (1 micron average) and has good adhesion to alloy. 4. Be is selectively oxidized and controlled the form of Cr2O3 and NiO.

Beryllium↗
PubMed2003

[A study on the color difference between Au-Pt alloy porcelain and Ni-Cr alloy porcelain].

OBJECTIVE: To investigate the color difference between Au-Pt alloy porcelain and Ni-Cr alloy porcelain. METHODS: 30 metal-ceramic specimens with different dentin porcelain thickness were fabricated with two types of metal-ceramic alloy, each type of alloy had 15 specimens. L*, a*, b* were measured after opaque porcelain was applied, and dentin porcelain was fired 1, 3, 5, 7 times by MINOLTA CR-100. Then delta E was calculated which reflected the color difference between high-gold alloy porcelain and Ni-Cr alloy porcelain. RESULTS: Comparing with Ni-Cr alloy porcelain, the color of Au-Pt alloy porcelain was reddish, yellowish and less bright. The delta E between high-gold alloy porcelain and Ni-Cr alloy porcelain in shade A2 was largest when opaque porcelain was applied. It decreased when dentin porcelain was applied. It became smallest when fired 3 times, and increased along with the increase of fire times. It was larger than 1.5 except firing 3 times. When dentin porcelain was applied, delta E which was larger than 1.5 among different dentin porcelain thickness decreased along with the increase of dentin porcelain thickness. CONCLUSION: The color difference between the two types of metal-ceramic alloy should be carefully taken into account in order to improve the quality of color matching.

Chromium↗
PubMed1987

Strength properties of soldered joints for a gold-palladium alloy and a palladium alloy.

Strength of a soldered palladium alloy, PGC (Engelhard Corp.), and a soldered medium gold alloy, PGX (Engelhard Corp.), was examined. The results obtained were as follows: Highest strength was observed with postsoldered specimens of PGC alloy. Microstructural examination of postsoldered specimens revealed nearly pore-free solder joints with PGC and PGX alloys, and fracture appeared at the solder-alloy interface with PGC and PGX alloys. Microstructural examination of presoldered and presoldered/thermocycled specimens revealed that presoldered specimens of PGC and PGX alloys exhibited intrasolder fracture; PGX solder joints had considerably less porosity, which may explain the equivalent bond strengths of all the soldered specimens and the yield point of the controls; PGC solder joints exhibited large quantities of pores, which may explain the lower strength; pores observed in PGC alloy may be the result of the high fusing temperature of the solder; and these results indicate a need to develop a new presolder for PGC. The best result was obtained with postsoldered specimens of the PGC alloy. However, for PGX alloy, either postsolder or presolder techniques can be used.

Dental Alloys↗
PubMed1996

Effect of alloy surface composition on release of elements from dental casting alloys.

The release of elements from dental casting alloys is a continuing concern because of the potentially harmful biological effects the elements may have on local tissues. The surfaces of the alloys appear to be most important in controlling the release of these elements. In the current study, the surfaces of high-, reduced-, and no-gold dental alloys were analysed by X-ray photoelectron spectroscopy before and after they were exposed to a biological medium for up to 96 h. The goal was to relate the release of elements from these alloys to their surface composition, and to determine the depth of the effect of the medium. The depth of the effect of the exposure was determined by argon milling of the alloy surface after exposure to the medium. Elements that were released into the medium were measured by means of atomic absorption spectroscopy. The release of elements from alloys was greater when the atomic ratio of noble to non-noble elements at the surface was less than 1. The depth of the effect of the medium varied with the alloy, but was always less than 100 A. The surface composition was significantly different from layers only 5 A below. It was concluded that the surface concentration of noble elements is important in controlling the release of non-noble elements from these alloys, and the surface composition appeared to be only one or two atomic layers thick. Of the three types of alloys, the high-gold alloy appeared to develop the most stable surface composition which released the lowest levels of elements.

Dental Alloys↗
PubMed1979

[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↗
PubMed1980

[Effects of Au content on ageing characteristics of Dental AG-Pd-Cu-Au alloys (I). Ageing characteristics of the alloys quenched from 800 degrees C designated by JIS as solution treatment temperature (author's transl)].

Commercial Ag-Pd-Cu-Au alloys of which Au content was changed form 0 to 50 wt. % were quenched from 800 degrees designated by JIS as solution treatment temperature and aged isochronically. The maximum hardness of the alloys by ageing decreased with increasing the Au content. Shape of age-hardening curve of the alloys was divided into two groups, one was of the lower Au content alloys containing below 30 wt. / Au and the other was of the higher Au content alloys containing more than 40 wt. % Au. As quenched structure of the lower Au content alloys was mixture of f.c.c alpha 2 phase and L20 type ordered phase (beta phase), on the other hand, the higher Au content alloys was composed simply by f.c.c alpha phase only. The maximum hardness of the lower Au content alloys given by ageing was caused by precipitates appeared at grain boundary, and of the higher Au content alloys was caused by precipitates in the grain were found. These facts may suggest that the mechanism of age hardening for the alloys change with increasing the Au content.

Chemical Phenomena↗
PubMed1980

[Studies on bonding between Ni alloys and porcelain--effect of addition of Cr and Co to Ni alloys (author's transl)].

Bonding between porcelain and Ni alloys containing 0 approximately 10 wt% Co and 0 approximately 25 wt% Cr is investigated. Experimental procedures are as follows. (a) Bonding strength between porcelain and alloys by pull out test (b) Expansion of alloys (c) Distribution of Ni, Co and Cr by EPMA (d) Macroscopic observation of fracture surface resulted by pull out test Following results were obtained 1) Pull out strength increased by addition of Co in all alloy systems. Pull out strength was lowest at 5 wt% Cr in Ni-Cr alloy system, at 15 wt% Cr in Ni-5 wt% Co-Cr alloy system, and at 20 wt% Cr in Ni-10 wt% Co-Cr alloy system. More addition of Cr increased the pull out strength. 2) The influence of alloying element on thermal expansion was not observed by addition of Cr and Co to Ni. 3) The thickness of the oxide film of alloys containing 5 wt% Cr was the largest, and it was remarkably decreased by more addition of Cr. 4) The fractography of porcelain showed a various patterns in relation to pull out strength. 5) At Ni-Cr-Co alloy surface oxide of porcelain side, Co concentration is slightly higher than Ni.

Chromium Alloys↗
PubMed1992

ESCA study on dental alloy surfaces modified by Ga-Sn alloy.

A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal alloys bonded with 4-META/MMA-TBB resin. However, there was no effect on the bonding of Ag-In-Zn alloy and base-metal alloys. In the present study, the alloy surfaces modified by the new method were analyzed by ESCA and SEM for determination of details of the modification effect. A new alloying layer containing Ga and Sn was formed on the precious-metal alloys. The main factor for excellent adhesion to be achieved was the formation of a very thin layer of Ga2O3 and SnO2, less than 1-2nm thick, on the alloy surface. A thicker modified layer, as formed on the Ag-In-Zn and Ni-Cr alloys, led to low bonding ability.

Acrylic Resins↗
PubMed1994

Study on the castability of Co-Cr alloy for cast plates. Part 4. Effects of sectional area, number of sprues and alloy components on castability.

Co-Cr alloy is used more frequently than Ni-Cr alloy as a nonprecious alloy for cast plates in Japan. Titanium with good biocompatibility has often been contained in the composition of this Co-Cr alloy. However, since the melting temperature of Co-Cr alloy is very high, about 1300 degrees C, and it oxidizes easily, a vacuum-pressure casting machine capable of melting this alloy in a reduced atmosphere has recently been developed. In this study, using the vacuum-pressure casting machine, the possible effects of sectional area and the number of sprues attached to the cast plate wax pattern, as well as the alloy components, on the castability of three kinds of Co-Cr alloy containing titanium were examined. It was found that all of these parameters had significant effects on Co-Cr alloy castability.

Chromium Alloys↗
PubMed1980

[Studies on Au-Ag-Pd-Cu alloys. (Part 2) Some properties on alloys containing 30 wt% Au (author's transl)].

In the previous paper, the author reported 30 wt% Au was more favourable content in Au-Ag-Pd-Cu quaternary dental alloys. In this paper, the experiment was carried out to find suitable Pd and Cu content in 30 wt% Au-Ag-Pd-Cu alloy. Pd and Cu content was changed from 5 wt% to 25 wt% and from 10 wt% to 20 wt% respectively. Ag content was balanced, and no other metals was added. Range of solidification temperature, tensile strength, elongation, hardness, corrosion resistivity and castability were tested. Results were as follows. 1) In these alloys, liquidus points were in the range of 880 degree C approximately 140 degree C, but in the majority of alloys, liquidus points were under 1100 degree C. Range of solidification temperature was more narrow in 20 wt% Cu than other Cu content. 2) The tensile strength and elongation of swaged specimens increased as Pd content increased, but in case of cast specimens, mechanical properties were the highest at 15 approximately 20 wt% Pd. The Vicker's hardness was in the range of 116 to 235. 3) The corrosion test in 0.1% Na2S solution indicated that the corrosion resistance was increased with Pd content and alloys contained more than 20 wt% Pd showed good resistance to corrosion. 4) The castability was affected by the Pd content and much decreased between 15 wt% Pd and 20 wt% Pd, but the castability of these alloys is twice as good as the alloys on the market. From these results, it seemed that the alloys containing 15 approximately 20 wt% Pd and 15 approximately 25 wt% Cu were more favourable composition to 30 wt% Au-Ag-Pd-Cu alloys.

Copper↗