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Biomedical subjects

E H Greener

Publications and source records attributed to E H Greener.

At least 55 records · Page 3Linked to original sources
PubMed1989

[Effect of Mo content and pH value on the corrosion behavior of Ni-20Cr-Mo dental alloys].

The results showed that the resistance against pitting corrosion in an acid milieu was dramatically improved by increasing the Mo content, while in a neutral milieu the pitting potential Ep remained unchanged. Remarkably, a Mo-content of more than 6 wt. % resulted in a further reduction in the pitting corrosion potential Ep, when pH 2 has been exceeded. A similar behaviour has been observed with the critical pitting potential Ec: Ec is also reduced at pH values between 3 and 7. To avoid pitting corrosion in the clinically relevant pH range of 4 to 7, a pitting resistance equivalent (PRE) of at least 43 is required.

Chromium Alloys↗
PubMed1988

Creep in a palladium-enriched high-copper amalgam.

Palladium additions to a dispersed phase high-copper amalgam have been shown recently to suppress markedly the eta' (Cu6Sn5) concentration and decrease creep. A detailed study of the dental and 24 h creep for Pd containing high-copper amalgams and six commercial controls as a function of applied temperature and stress was performed. One part of Ag-Cu or Ag-Cu-Pd dispersants with substitutions of up to 20wt/o Pd for either Ag or Cu was blended with two parts of traditional amalgam alloy. Various temperatures from 25 to 60 degrees C and stresses from 36 to 72 MPa were applied to the samples during the test. For commercial controls and experimental amalgams with no Pd, creep is a strong function of temperature and stress. The experimental amalgam containing up to 10wt/o Pd, Pd substituted for Ag, demonstrated essentially constant creep over the temperature and stress range applied.

Chemical Phenomena↗
PubMed1988

The corrosion resistance of a new cobalt-chromium-molybdenum-ceramic alloy.

Cobalt-chromium alloys are extensively used for removable partial dentures and implants. Recently, this type of alloy has been introduced for porcelain-fused-to-metal crown and bridgework. The objective of this in vitro study was to evaluate the corrosion behaviour of such a ceramic alloy (Vicomp) and compare it to a cobalt-chromium alloy for removable partial dentures (Vitallium). A 0.9% saline solution and an artificial saliva were used as electrolytes. Results indicate a similar, adequate, corrosion resistance.

Ceramics↗
PubMed1988

Degree of conversion of seven visible light-cured posterior composites.

The infrared spectra of seven commercially available posterior composite resins were analysed by ratioing the C = C aliphatic peak to the C = C aromatic peak. The degree of conversion ranged from 43.5 to 73.8%. The result was similar to the range previously obtained from unfilled Bis-GMA based resins and commercial anterior composites.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1988

Metallurgical aspects of high-palladium alloys.

Nine commercial high-Pd alloys were investigated. Microstructure and phase composition were screened by x-ray diffraction, light microscopy, and an electron microprobe. After being etched, some high-Pd alloys revealed dendritic structures. The others showed a more homogeneous structure with distinct grain boundaries. Etching was necessary to reveal distinct structures, though the overall etching effect turned out to be limited. On unetched specimens, only a slight chemical heterogeneity could be determined. Except for one alloy, the systems turned out to have complex multi-phase structures. The main face-centered-cubic (fcc) phase was Pd-based. As secondary phases, body-centered-cubic (bcc) and/or simple cubic ones were detected. The latter phases were similar to a Cu3Ga and PdGa intermetallic compound, respectively. Face-centered-tetragonal (fct) structures reported by other investigators were not found.

Chemical Phenomena↗
PubMed1987

Corrosion of ferromagnetic alloys used for magnetic retention of overdentures.

Three ferromagnetic casting alloys intended for use with magnetically retained overdentures (compositions in wt%: #1, Pd 50, Co 47, Ga 2, Pt 1; #2, Pd 60, Co 37, Ga 2, Pt 2; #3, Pd 49, Co 46, Ga 2, Pt 2) were investigated. A 0.9% saline solution and an artificial saliva (Meyer) were used for evaluation of the electrochemical corrosion behavior of these alloys, utilizing standard potentiodynamic techniques. All alloys investigated possessed a good corrosion resistance in the potential range of the oral environment (from -100 to 300 mV versus SCE). In addition, alloys #1 and 3 appeared to be susceptible to pitting above +300 mV (SCE), while #2 was resistant to pitting and was found to passivate in 0.9% saline solution.

Chromium Alloys↗
PubMed1986

The effect of resin formulation on the degree of conversion and mechanical properties of dental restorative resins.

The goal of this study was to determine the effects of resin formulation variables, such as diluent concentration, catalyst type and concentration and cure mode, on the degree of conversion of carbon double bonds and mechanical properties of dental restorative resins. Diametral tensile strength, compressive strength, hardness, flexural modulus and strength, and dynamic mechanical properties were tested, and the results were correlated to the degree of conversion results obtained by infrared analysis. The results showed a significant correlation between increased mechanical properties and higher degrees of conversion. Enhanced conversions were achieved by incorporating higher diluent and lower inhibitor concentrations into the resins. Ambient temperature properties were similarly enhanced by lower inhibitor concentrations, but were not enhanced by higher diluent concentration. Dynamic mechanical properties testing at oral and elevated temperatures elucidated possible differences in resin microstructure and network quality. The storage moduli decreased over the dental temperature range and was lower at all temperatures for resins with lower conversions. The glass transition temperature was also lower in resins with poorer conversions, suggesting that these resins may be more unstable at oral temperatures than more highly converted resins. Dynamic mechanical properties were most closely correlated to degree of conversion in these polymeric systems.

Acrylic Resins↗