On Creep Mechanisms in Amalgams

Herø, H.

doi:10.1177/00220345830620011001

Cited by 18 publications

(7 citation statements)

References 18 publications

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“…Theoretically, creep in amalgam occurs by plastic flow and grain-boundary sliding. 33 According to Xu et al, 34 subsurface creep of indentation area is dominated by deformation of individual alloy particles as well as matrix grains, which are associated with the creep-induced shape changes of individual alloy particles from spherical to irregularly elongated shapes, and the matrix grains separating them from each other possible due to plastic flow and/or grain rotation. The black arrow in Fig.…”

Section: The Metallic-like Deformation Properties Of Enamelmentioning

confidence: 99%

Enamel—A “metallic-like” deformable biocomposite

Swain

2007

Journal of Dentistry

129

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Section: The Metallic-like Deformation Properties Of Enamelmentioning

confidence: 99%

Enamel—A “metallic-like” deformable biocomposite

Swain

2007

Journal of Dentistry

129

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“…The activation energy ranged from 81.6-110 kJ/mol. Hero (1983) found m = 2.50-2.79 for two conventional amalgams and a high-copper admixture in the compressive stress range of 20-57 MPa.…”

Section: Introductionmentioning

confidence: 95%

“…1 has been used by Vrijhoef and Driessens (1974a) and by Hero (1983) where the effective stress, c 0-cfo consisting of the applied stress minus an internal or back stress, is substituted for a7. As a result, values of the stress exponent were found to be about 2.…”

Section: Introductionmentioning

confidence: 99%

“…Most studies of amalgam creep have found m to be from 2 to 3 (Vrijhoef and Driessens, 1972;Espevik, 1977;Hero, 1983). From the stress dependence of creep and from microstructural observations, it has been concluded that the dominant mechanism of amalgam creep is grain-boundary sliding with accommodation by dislocation slip in the mantle of the Yi grains (Okabe el al.. 1983;Hero, 1983). Greener et al ( 1 980, 1982) have modeled the time-dependence of the creep rate using the Cottrell equation:…”

Section: Introductionmentioning

confidence: 99%

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Creep of Amalgam at Low Stresses

1987

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The creep and recovery of dental amalgam were studied with a torsional creep apparatus. The purpose was to investigate viscoelastic behavior in a low stress range that might result from normal chewing forces. The creep of specimens up to six months old was also studied. Four types of alloys for amalgam were used: two single-composition sphericals (SCS), an admixture-lathe-cut eutectic (ALE), and a conventional (CON). Constant torque was applied to dumbbell-shaped specimens for three hr and, after the stress was released, recovery was followed for 50 hr. All measurements were made in water at 37 degrees C after storage of the specimens for one week in 37 degrees C water. Creep was also measured at nine intervals on specimens aged from three hr to six months. The SCS amalgams exhibited the least amount of creep, followed by the ALE amalgam. The CON amalgam had the highest creep. The SCS amalgams approached linear viscoelastic behavior in the shear stress range of 0.78-4.10 MPa at 37 degrees C. They did not exhibit steady-state (viscous) creep at stresses less than 4.10 MPa. Recovery was complete but proceeded more slowly than creep. The ALE and CON amalgams exhibited viscous creep at 1.23 MPa and higher. The steady-state creep rate depended on stress, and the stress exponent ranged from 2.3-3.5. All except the ALE amalgam showed essentially constant creep compliance when aged up to six months, once the amalgamation reaction was completed after 24 to 48 hr. The compliance of the ALE amalgam gradually decreased over the six-month period.

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“…The creep tests performed on amalgam generally involved the deformation of the bulk specimen in compression (Her0, 1983), tension (Papadogiannis et al, 1987), and dynamic configurations (McCabe and Carrick, 1987). These tests have provided important information on the time-dependent deformation of amalgam, establishing relationships among creep, microstructure, marginal breakdown, and corrosion.…”

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confidence: 99%

Indentation Creep Behavior of a Direct-filling Silver Alternative to Amalgam

Liao

Eichmiller

1998

J Dent Res

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Amalgam creep has been identified as a key parameter associated with marginal breakdown and corrosion. The aim of this study was to evaluate the time-dependent deformation (creep) of a novel silver filling material as an alternative to amalgam. We made the silver specimens by pressing a precipitated powder at room temperature to a density that can be achieved in clinical hand consolidation. The surface of the silver was either polished or burnished. To examine local contact creep and the effect of surface finishing, we used an indentation creep method in which a Vickers indenter was loaded on the specimen surface at a load of 10 N with dwell times of 5 sec to 6x10(4) sec. We used a bonded-interface technique to examine subsurface creep mechanisms. The flexural strength (mean+/-SD; n = 10) was 86+/-20 MPa for amalgam, 180+/-21 MPa for polished silver, and 209+/-19 MPa for burnished silver-values which are significantly different from each other (family confidence coefficient = 0.95; Tukey's multiple-comparison test). Indentation creep manifested as hardness number decreasing with increased dwell time. With dwell time increasing from 5 sec to 6x10(4) sec, the hardness number of amalgam was reduced by approximately 80%; that of the polished silver and the burnished silver was reduced by only 40%. Subsurface creep in amalgam consisted of the shape change of the alloy particles from spherical to elongated shapes, and the separation of matrix grains from each other, possibly due to grain-boundary sliding. Creep of the polished silver occurred by densification reducing porosity and increasing hardness; that of the burnished silver occurred by the displacement of the burnished layer. These results suggest that, due to creep-induced subsurface work-hardening and densification, the consolidated silver exhibits a higher resistance to indentation creep than does amalgam. The hardness number of silver approaches that of amalgam after prolonged indentation loading.

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On Creep Mechanisms in Amalgams

Cited by 18 publications

References 18 publications

Enamel—A “metallic-like” deformable biocomposite

Enamel—A “metallic-like” deformable biocomposite

Creep of Amalgam at Low Stresses

Indentation Creep Behavior of a Direct-filling Silver Alternative to Amalgam

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