Creep, corrosion and marginal fracture of dental amalgams

Sarkar, N. K.

doi:10.1111/j.1365-2842.1978.tb01260.x

Cited by 35 publications

(19 citation statements)

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“…Lack of good condensation is one among several manipulative variables that may influence the mercury content and the morphologies and volume fractions of the different phases (13,14). Thus the lack of relationship to the cavity volume but not to cavity depth indicates that the effect of the condensation time or the condensation pressure cannot explain the observed increased degradation in the deep cavities.…”

Section: Discussionmentioning

confidence: 99%

Influence of cavity depth on marginal degradation of amalgam restorations

Jokstad

1991

Acta Odontologica Scandinavica

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Jokstad A. Influence of cavity depth on marginal degradation of amalgam restorations. Acta Odontol Scand 1991;49:65-71. Oslo. ISSN 0001-6357. In a 5-year clinical trial it was observed that the marginal degradation of class-II amalgam restorations could be related to the bulk of the restoration. The association between the occlusal cavity depth and the marginal degradation was observed after 6 months and varied for the different-types of alloy. Ridit scores of the marginal degradation were correlated to various indices of the cavity sizes, to assess the possible reason for this association. The possibilities of the relationship being an indirect effect caused by longer condensation times or by poorer condensation due to the use oflarger condenser sizes were rejected. Furthermore, the possibility that the association was the result of potential buildup of stresses on the restoration margins caused by flexible cusps and axial walls was not apparent. A possible mechanism may be that marginal degradation is the result of short-term or long-term expansion, or even extrusion of amalgam. Expansion may theoretically be caused over short periods by temperature changes or over long periods by corrosion or phase shifts in the amalgam. The theory does not exclude the role of creep or corrosion artd may furthermore explain the lack of correlation between in-vitro tests and in-vivo performance of amalgam restorations. D Clinical study; dental materials; expansion; marginal ditch; operative dentistry Asbj~m Jokstad,

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Section: Discussionmentioning

confidence: 99%

Influence of cavity depth on marginal degradation of amalgam restorations

Jokstad

1991

Acta Odontologica Scandinavica

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“…Dental amalgam creeps and the specimens were subjected to both a temperature near 0.9 Tm (50 C) (Sarkar, 1978) and to low-frequency cyclic stresses as the result of thermal cycling. Since margin fracturing increased with cycling time, the fracture is timedependent, and is probably related to time-dependent phenomena such as creep.…”

Section: Methodsmentioning

confidence: 99%

“…Although a good correlation was found between gamma-2-free and gamma-2-containing alloys, no correlation was found within the gamma-2-free alloys . Sarkar (1978) explains this discrepancy by stating that the elimination of the gamma-2 phase occurs coincidentally with a reduction in creep, but, once this phase is eliminated, further reductions in creep are not necessarily accompanied by decreased corrosion and better margin integrity.…”

Section: Introductionmentioning

confidence: 90%

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Creep-fatigue as a Possible Cause of Dental Amalgam Margin Failure

Williams

Hedge

1985

J Dent Res

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Fracture of the margins is the most common cause of failure of dental amalgam restorations. Both corrosion and creep have been identified as possible contributors to this type of failure. The stresses that induce creep may arise from the continued setting expansion of the amalgam, the formation of corrosion products, mastication, or from the thermal expansion of the amalgam during ingestion of hot foods. The latter two are low-frequency cyclic stresses. The amalgams used in dentistry have fusion temperatures only about 40 degrees C above mouth temperature, and they experience grain boundary sliding during creep deformation. Since grain boundary sliding, low-frequency cyclic stresses, and a temperature near the fusion temperature of the alloy are prerequisites for so-called "creep-fatigue fracture", this type of fracture may contribute to amalgam margin failure. Amalgam made from seven different alloys was condensed into stainless steel dies. After being allowed to set for seven days, the specimens were thermally cycled between 4 degrees C and 50 degrees C for 500 and 1000 cycles. Amalgam margin integrity was evaluated by scanning electron microscopy both before and after each cycling period. The amount of margin fracture was calculated after 1000 cycles. Thermal cycling of amalgam restorations placed in stainless steel dies resulted in predominantly intergranular fracturing of the amalgam margins, indicating that creep-fatigue failure may be a significant contributor to in vivo margin fracturing.

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“…13,14,18,19 Clearly, there is a need for an alternative in vitro test which correctly predicts the relative marginal fracture of dental amalgams, regardless of their nature. Based on the premise that marginal fracture is an effect of corrosion, 10,16,17,[20][21][22][23] it is strongly felt that a corrosion test might serve this purpose. In order to demonstrate corrosion as a viable and dependable test, it is essential that a correlation between in vitro corrosion and in vivo marginal fracture first be established.…”

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confidence: 99%

In vitro Corrosion and in vivo Marginal Fracture of Dental Amalgams

1982

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The relationship between in vitro corrosion and in vivo marginal fracture of dental amalgams has been studied. The potentiodynamic cyclic polarization technique has been used to determine the in vitro corrosion index. The marginal fracture data have been obtained from previous clinical studies reported by three independent research groups. A linear regression analysis has been employed to determine the degree of correlation between in vitro and in vivo data. Depending on the method of corrosion index measurement and the source of clinical data, correlation coefficients (r) ranging from 0.82 to 0.94 (p less than .01) have been obtained.

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Creep, corrosion and marginal fracture of dental amalgams

Abstract: Summary An analysis of the available information on creep and corrosion of dental amalgams is presented in an attempt to understand their role in the marginal breakdown of amalgam restorations.

Cited by 35 publications

References 54 publications

Influence of cavity depth on marginal degradation of amalgam restorations

Influence of cavity depth on marginal degradation of amalgam restorations

Creep-fatigue as a Possible Cause of Dental Amalgam Margin Failure

In vitro Corrosion and in vivo Marginal Fracture of Dental Amalgams

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