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Biomedical subjects

R A Fuys

Publications and source records attributed to R A Fuys.

7 recordsLinked to original sources
PubMed1981

The tooth-amalgam interaction.

The interaction between tooth and amalgam during in vitro corrosion of dental amalgams has been studied in this investigation. Extracted teeth have been restored with five commercial amalgams, one of which was gamma 2 -free and the others contained the gamma 2-phase. The restored teeth were immersed in a 1% NaC1 solution for 9 months. Post corrosion restorations have been examined by optical microscopy, scanning electron microscopy, and X-ray microanalysis. The results are: (1) gamma 2-containing amalgam surfaces were covered with Ca-Sn-P-rich corrosion products of various morphology which occasionally contained relatively low concentrations of C1 and/or Zn; (2) the corrosion products on the gamma 2-free amalgam surface indicated relatively high concentrations of Hg in addition to Ca, p, Sn, Cu, and Zn. These results agree with the past observations that corrosion of amalgam restorations is not an isolated process. Rather it may involve reactions of the restoration and the surrounding oral environment including tooth and oral fluids in which interactions of Sn, Zn, Hg, Ca and P take place.

Calcium↗
PubMed1979

The chloride corrosion of low-gold casting alloys.

Potentiodynamic polarization measurements have indicated that the so-called 'low-gold' casting alloys are characterized by decreased chloride corrosion resistance, when compared with ADA Type III and Type IV gold alloys. This decrease in chloride corrosion resistance results apparently from the presence of Ag-rich microsegregations with a possible minor contribution from Cu-rich segregations or precipitates.

Chlorides↗
PubMed1979

The chloride corrosion behavior of silver-base casting alloys.

The chloride corrosion behavior of five silver-palladium dental casting alloys was investigated in a 1% NaCl solution through the use of electrochemical hysteresis technique. The corrosion mechanism has been interpreted in terms of the microstructure of these alloys and their possible electrochemical reactions.

Corrosion↗
PubMed1976

Physical properties of a nickel-base alloy prepared by isostatic pressing and sintering of the powdered metal.

The physical and mechanical properties of samples of a nickel-base alloy fabricated by powder metallurgy were determined. The particle sizes of the powders used to make the samples varied from -80/ +200 mesh to -325 mesh. The compaction pressure varied from 138 to 414 MN/m2 and the sintering temperature varied from 1150 to 1250 degrees C. The shrinkage during processing, the porosity, tensile strength, yield strength, elongation, and elastic modulus were used to characterize the samples. The strength of the samples generally increased with decreasing particle size of the powder and increasing compaction pressure and sintering temperatures. The porosity and strength, therefore, could be varied over a wide range by controlling the various parameters. The properties of the samples prepared by powder metallurgy were compared with those of the cast alloy and compact bone. Conditions can be selected that will yield equivalent or better properties by powder metallurgy than by casting.

Bone and Bones↗
PubMed1976

Characterization of porosity of isostatically pressed and sintered nickel-base powdered metal.

Characterization of the pore structure of compacted and sintered parts made from a nickel-base powder was accomplished using the mercury porosimetry method. The theoretical density values for the sintered specimens varied from 56.3 to 96.7% which corresponds to a porosity of 43.7 to 3.3%. A maximum interconnecting median pore diameter of 21 mum resulted from a -80/+200 mesh powder compacted at 138 MN/m2 and sintered for 2 h at 1250 degrees C. Photomicrographs of the same sample showed that it had a maximum pore diameter of 200 mum. The interconnected pore volume decreased with decreasing particle size of the powder, increasing compaction pressure, and increasing sintering temperature. Mechanical properties of tensile strength, yield strength, elastic modulus and percentage elongation were correlated with the pore structure. Proper selection of particle size, compaction pressure, sintering times and sintering temperatures should permit parts with controlled porosity characteristics to be produced that possess adequate mechanical properties for application as implants.

Chemical Phenomena↗