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At least 19 recordsLinked to original sources
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↗
PubMed1979

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.

Dental Alloys↗
PubMed1978

Powder data file as a tool for identification of dental gold alloys.

In order to obtain data for a prospective powder data file for dental gold alloys X-ray diffraction photograms of 75 different gold alloys were taken using a Guinier-Hägg camera and CuKalpha1 radiation. Before the X-ray photograms were taken the alloys had been heat treated at 700 degrees C, 800 degrees C or 900 degrees C depending on the solidus temperatures of the alloys. The lattice parameters of the samples were determined from the X-ray photograms. These data were supplemented by a specification of the interplanar spacings of the three strongest lines on the diffraction patterns and also by the relative intensities and Miller indices of these lines. An extensive library of reference films is to be collected and this and other details of the file are discussed. It is not intended that the file be used to identify a particular alloy but merely to identify the type of alloy. Thus it can serve as a guide to facilitate the proper selection of gold alloys within practical clinical dentistry.

Filing↗
PubMed1979

Casting a gold alloy to embedded precision attachment metals.

The technique for casting a gold alloy to embedded attachment metals has been described. The joints of gold alloy cast to commercially available attachment metals were examined with a metallurgic and a scanning electron microscope. The investigation indicated that an uninterrupted gapless joint is possible, and that some diffusion occular along the interfaces with some attachment metals. In view of these findings, it is concluded that this technique can be recommended as a dental laboratory procedure.

Dental Alloys↗
PubMed1979

Minimizing costs for casting gold alloy in student preclinical courses and commercial laboratory clinical use.

With inflation producing a consistantly rising price for casting gold alloy, student use in preclinical courses and clinic use in commercial laboratory castings represent a significant cost to the student and the school. The New Jersey Dental School has developed and instituted a plan to decrease student cost and manage commercial laboratory fees by the purchase of a year's supply of gold. Students use the gold alloy and pay only for lost amounts, while the school replaces the gold used by the commercial laboratory.

Dental Casting Investment↗
PubMed1977

[Recrystallization process in the 20 carat dental gold alloy (author's transl)].

An annealing process of the 20 carat dental gold alloy was studied by hardness testing, electrical resistivity measurement and optical microscopic observation. The material was cold rolled to 67.4% and 90.7% in reduction and subsequently annealed in the temperature range from 300 degrees to 500 degrees C. Microscopic observation, electrical resistivity and hardness testing revealed that the annealing process were three distinguishable stages, recovery, recrystallization and grain boundary migration. Activation energies, the order of the reaction involved, and frequency factors for various annealing processes were established.

Crystallization↗
PubMed1977

Correlation between strength and hardness of dental casting gold alloys.

The yield strength, tensile strength, and hardness of Type IV dental casting gold alloys were measured. Regression lines and prediction intervals for the estimation of yield strength and tensile strength from hardness measurements were then determined. The 95% prediction intervals for the yield strength and tensile strength were found to be +/- 45 MN/m2 and +/- 105 MN/m2, respectively.

Dental Casting Investment↗
PubMed1975

A resistometric study of order-hardening in dental gold alloys.

The ordering process in gold-copper-silver dental alloys was studied by means of isochoronal and isothermal resistivity measurement. Because the stable existing temperature range of orthorhombic superlattice was unexpectedly extended to lower temperature by the addition of silver to gold-copper binary alloy, the ordering velocity in these alloys are considerably slower than that of binary stoichiometric AuCu alloy. Activation energy, the order of the reaction, and rate constant for growing process were established. The difference in growing mechanisms depending on gold concentration was deduced from the kinetics data.

Copper↗
PubMed1976

Microstructure of the solder-casting zone in bridges of dental gold alloys.

The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.

Dental Soldering↗
PubMed1975

[Studies on the dental gold-alloys (14). Effect of platinum addition on the AuCu-transformation by means of x-ray diffraction analysis (author's transl)].

X-ray diffraction studies were carried out so as to investigate the effects of 0.33-6.90 at. % additions of platinum on the ordering process of AuCu alloy. The stable existing temperature range of AuCu I was extended to higher temperature by the addition of platinum to stoichiometric gold-copper alloy, the ordering rate in these alloys were slower than that of binary AuCu. Changes in diffraction patterns showed a different sequence in ordering process at higher and lower temperature range. Orthorhombic AuCu II was only found in the alloy containing 0.33 at.% Pt at around 410 degrees C.

Copper↗