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At least 19 recordsLinked to original sources
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↗
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↗
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↗
PubMedDate not supplied

[Effect of electrochemical etching of alloy surface (Wiron 88 and Wironit) on the strength of alloy binding to enamel by the Microjoin cement].

One of the methods of "adhesive" preparation of the surface of the retention elements of AET bars and brides before their binding to enamel is electrochemical etching. The purpose of the method was creation on alloy surface of appropriate microretention for the fixing resin. The aim of the study was determination of the optimal conditions for etching of alloys (Wiron 88 and Wironit) as binding elements of AET constructions, and for checking the binding force of the Microjoin resin cement. The following etching conditions were accepted as optimal: for the Wiron 88 alloy (10 min, 2,7 V, 200 mA/cm2), for the Wironit alloy (12 min, 2,7V, 270 mA/cm2). The binding force of the alloys etched under optimal conditions to the enamel achieved with the Microjoin (Sci-Pharm-Madental) resin cement was measured also, using the Instron testing device. The movement velocity was 2 mm/min. The following strength of binding of etched alloys to enamel was measured: 195.7 kG/cm2 for the Wiron 88 alloy, and 128.6 kG/cm2 for the Wironit alloy.

Acid Etching, Dental↗
PubMed1979

Evaluation of alternative alloys to precious ceramic alloys. 1. Mechanical properties.

In the first part of this study, the microstructures and the mechanical properties of precious, semi-precious, and nonprecious dental casting alloys for the porcelain-baked-to-metal technique have been determined. The semi-precious alloys contained only 50% gold, and palladium, silver, and some base metals. The nonprecious alloys were of the nickel-chromium type. Discs and miniaturized tensile bars have been cast and tested either in the as cast condition, or after a simulation of the various porcelain bakes. Proof stress, ultimate tensile strength, elongation, and plastic stiffness have been measured and results compared by use of analyses of variance. The microstructure examination shows that the simulation of the porcelain bakes improves the homogeneity of the precious and semi-precious alloys. Simultaneously, the mechanical properties of the same alloys are also improved. One semi-precious alloy, still under development at the time of these tests, has its mechanical characteristics markedly downgraded by the thermal treatments. The nickel-chromium alloys exhibit the best range of mechanical properties for the porcelain-baked-to-metal technique, when considering the three most relevant properties: proof stress, plastic stiffness, and modulus of elasticity.

Chemical Phenomena↗
PubMed1979

[Casting of dental alloys with special reference to the bonding capacity of Ni-Cr alloys].

A short review on castability of dental alloys -- for which a definition is proposed -- reflects the different factors influencing the results of a casting. In this case solid sieves and plates are cast by use of one gold-base alloy (Type III) and two base metal alloys used for porcelain veneering. All three alloys filled the sieve pattern to a 100%, whereas they performed differently when cast as thin, solid squares. The most continuous results were achieved with a Ni-Cr-alloy whose melting temperature can be recognized since the ingots flow together when this point is reached. Since the plate pattern is most difficult to cast due to surface to bulk ratio it is assumed that a complete casting can only be achieved when the performance of the alloy is good and all required conditions match. Thus, this type of test seems to be suitable to determine the castability of a dental alloy. The sieve test should be used to investigate and to improve the influence of the different factors as for example burnout time and temperature of the mold and sprue size.

Chromium↗
PubMed1990

[Metal alloys for ceramic veneering and special methods of handling precious-, palladium- and non-precious alloys].

Out of the great number of very important investigations on metal ceramics, only a small section can be represented. Those precious metal alloys which were developed for metal ceramics 25 years ago, were able to create and body confidence in the new ceramic proceedings of production for crowns and bridges. The number of failure caused by cracking and bursting was of a minor kind. The necessity of having cheaper alloys at one's disposal, e.g. gold-reduced alloys, palladium-alloys and non-precious metal alloys, involved that investigations for locating mistakes in the ceramics were carried through. Afterwards, changes of working methods had to be tested, in order to eliminate bubbles and cracks. The demonstrated results are designed to achieve better crowns and bridges. Allbountiful instructions are not possible, however, each alloy and each ceramic mass requires a special method of handling. If this happens, metal ceramics should continue to be a valuable clinically practicable method.

Dental Alloys↗
PubMed1977

[Bond strength between nonprecious metal alloy and porcelain. (Part 2) Effects of the addition of Mn, Mo, Si, Sn, Ta and Ti on bond strength of 80 Ni-20 Cr alloy (author's transl)].

Alloys added 2, 4 and 6 wt% Mn, Mo, Si, Sn, Ta and Ti to 80 wt% Ni-20 wt% Cr alloyand no-added 80 wt% Ni-20 wt% Cr alloy were prepared and casted to obtain the test specimens 3 mm in diameter 25 mm in length. Ceramco porcelain (B.F. Vacuum Porcelain) was fused to each of these specimens, and the bond strength was measured by the pull-out method which applies shear stress to the metal/porcelain interface to investigate the effect of each addition element. The test results may be summarized as presented below. 1) The bond strength between the 80 Ni-20 Cr alloy and the porcelain was 182 +/- 14 kg/cm2. 2) Of the six kinds of addition elements, it was Mo, Sn, Ta and Ti that increased the bond strength. 3) The bond strength between the alloy added 6 wt% Ti to the 80 Ni-20 Cr alloy and the porcelain was 319 +/- 8 kg/cm2, which was increased by about 75% over the strength between the 80 Ni-20 Cr alloy and the porcelain.

Chromium↗
PubMed1977

Influence of the heat treatment of commercial amalgam alloys on the phase composition of the alloys and the creep of the resulting amalgams.

The influence of heat treatment of dental alloys at several temperatures on the phases present in the alloy and the creep of the resulting amalgam as well as the correlation between phase changes and the creep was investigated. A dependence of the creep on the temperature of the heat treatment of the alloy was established. Substantial phase changes were observed after the different heat treatments. No correlation was detected between the creep rate and the changes in phases present in the dental alloys. A thermodynamically oriented explanation of the relation between the creep of the amalgam and the state of (non-) equilibrium of the corresponding amalgam alloy was proposed and discussed.

Dental Alloys↗
PubMed1990

[Cracking in laser welds of dental Ni-Cr alloys. Effect of alloy composition].

For the purpose of clarifying the effect of alloy compositions on cracking in laser welds of dental Ni-Cr alloys, 12 commercial and 11 experimental Ni-Cr alloys for crown and bridges were subjected to pulsed YAG laser spot welding, and their welds were investigated by optical and scanning electron microscopy, and EDX and thermal analysis methods. Main conclusions are as follows. 1. Cracks in laser welds were solidification cracks at grain boundaries in weld fusion zones. 2. In the case of commercial dental Ni-Cr alloys, a considerable number of eutectics enriched in Si, A1 and/or S were formed. Greater cracking susceptibility was interpreted by considering that these eutectics solidified at solidification temperatures far lower than the nominal solidus. 3. In the case of experimental Ni-Cr alloys with a small amount of eutectics, S and Si enhanced cracking sensitivity, but Mn reduced cracking. 4. The above results suggest that it is beneficial to the prevention or reduction of cracking to decrease harmful elements such as Si and S forming low solidification temperature eutectics or to add some elements such as Mn forming higher solidification temperature eutectics instead of lower ones.

Chromium Alloys↗
PubMed1976

[Studies on the dental gold-alloys. (15). On the age-hardening in AuCu-Pd alloys (author's transl)].

The effects of Palladium addition to stoichiometric AuCu on the age-hardening are studied by means of resistivity, hardness, X-ray diffraction, and optical and electron microscopic observation. The results obtained are summerized as follows. The shapes of the age-hardening curves in the alloys less than 23.4 at. % Pd, showed an abrupt increase at the early stage of ageing. However, in the alloy containing 34.4 at. % Pd, the age-hardening was not observed. The maximum hardness of the AuCu-12 at. % Pd alloy was higher than that of the AuCu-6 at. % Pd and AuCu-23.4 at. % Pd alloys. The difference in hardening in these alloys was explained by the effect of atomic sites of palladium occupied in AuCu superlattice. Optical and electron micrographs showed that twinning occurs in order to relief the elastic strain induced by growth of AuCu I type superlattice platelets.

Copper↗
PubMed1976

[A pattern analysis of stress-strain curves for Ag alloys. (Part 1) On stress-strain curves for Ag-Cu alloys (author's transl)].

Mechanical properties of the dental metals have been estimated from the value of tensile strength, yield point, elastic limit, elongation and so on. But when applying these values to practical dental problems, they are often find to be not available enough. And recently the electoronic computer has been developed and widyly used in various fields, so the author tried to analyze true stress-true strain curves for alloys as pattern by the computer. The flow curves in the region of uniform plastic deformation was expressed by the Hollomon model, sigma=FepsilonN, and in this paper, Ag-Cu alloys were studied in various contents and heat treatments. Results obtained are as follows [1] Theoretically, the equations should hold between experimental values--epsilonT, ST and calculated values --N, F(F/e)N, that is epsilonT=N, and ST=F(N/e)N. In the case of Ag-Cu alloys, these relations agree well with the theoretical equations. In other words, the shape of true stress-true strain curves for Ag-Cu alloys almost coincide with the theoretical approximate curves, sigma=FepsilonN. [2] Strain hardening exponent N is very dependent on the micro structures of Ag-Cu alloys, but plastic coefficient F is independent of the micro structures. Coefficient F is directly proportional to sigma T. [3] The relationship of F to N can be expressed by equation of F=R(N+1)/NN+1. This equation may be described to be another form of the strain energy equation. Therefore parameter R is dependent on the strain energy. And the plots by computer agreed well with the experimental values.

Copper↗
PubMed1992

The base metal alloy question in removable partial dentures--a review of the literature and a survey of alloys in use in Alberta.

Base metal alloys have been used for over 60 years to cast removable partial denture frameworks. Among other elements, these alloys principally contain nickel, chromium and cobalt, and may be divided into the nickel-containing and nickel-free alloys. Because of the potential biocompatibility hazard created by these and other elements found in the alloys, this group of materials has come under ever increasing scrutiny in the literature. This paper reviews pertinent literature and reports on the findings of a survey on the base metal alloys used in Alberta for the casting of removable partial denture frameworks.

Beryllium↗
PubMed1978

Corrosion behavior of cast and forged cobalt-based alloys for double-alloy joint endoprostheses.

An ideal combination of mechanical and corrosion properties of long-term implants such as joint endoprostheses has yet to be found. Besides being resistant to pitting and crevice attack, which can lead to corrosion fatigue and stress corrosion cracking failures, the implant material must be highly resistant to wear and abrasion. Two cobalt-based alloys, wrought CoNiMoTi and air-cast CoCrMo, were subjected to a number of selected in vitro electrochemically and chemically accelerated corrosion tests in chloride-containing solutions with wrought AISI-316L used as a reference alloy. A limited number of immersion tests in FeCl3 and acidified FeCl3 solutions were also conducted. It is found that the mechanical properties of wrought CoNiCrMoTi alloy qualify it as a substitute for cast CoCrMo alloy and wrought AISI-316L in anchorage shaft production for all types of joint endoprostheses. Wrought CoNiCrMoTi has a higher resistance to fatigue cracking compared with cast CoCrMo and is as resistant to selective corrosion phenomena such as stress corrosion cracking.

Alloys↗
PubMed1991

Veterans Administration Cooperative Studies Project No. 147. A precementation comparison of metal ceramic restorations made with a gold-containing alloy or alternative alloys.

This analysis compared the precementation quality of metal ceramic restorations made from different alternative alloys after they had been returned from the central dental research laboratory. Ticon, Micro-Bond N/P2, Ceramalloy II, and W-1 materials were evaluated by use of 11 well-defined criteria and for overall performance. The evaluations were compared with those of Olympia, a gold-containing alloy, which served as the control. The results showed statistically significant differences between Olympia alloy and some of the alternative alloys for six of the 11 criteria. These differences, however, were not sufficient to be considered clinically significant (clinically detectable). In the comparison of their overall performances no statistically significant differences were found.

Corrosion↗
PubMed1975

[Studies on the dental gold-alloys (13). Precipitation hardening in gold-cobalt alloys (author's transl)].

The precipitation of cobalt from gold-rich solid solution was studied about Au-Co binary alloys containing less than 5 wt.% cobalt by correlating the results of metallographic observation and micro-hardness measurement to electrical resistivity measurements. The hardness curves of the alloys showed to hardness peaks after isothermal ageing below a certain temperature. It was considered that the first peak was due to formation of G. P. zone which was confirmed by reversion phenomenon. The second peak was due to growing of metastable cobalt rich precipitate. The maximum hardness obtained by ageing was higher in Au-5 wt.% Co alloy than in Au-1 wt.% Co alloy. Difference in growing mechanism of metastable precipitate was deduced from the kinetics data and the values of time exponent obtained by Johnson-Mehl equation.

Cobalt↗