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At least 973 records · Page 54Linked to original sources
PubMed1995

Corrosion and creep resistance of some dental amalgam alloys.

Corrosion behaviour, creep values and phase transformation of conventional, admixed, unicompositional and two palladium-enriched amalgam alloys were investigated. Weight-loss method and solution analysis for dissolved metal ions were used. Creep values were determined after different immersion periods. X-ray diffraction was carried out to follow up phase transformation after different immersion periods and/or aging in dry air at 37 degrees up to one year. The results have shown that addition of palladium has improved corrosion and creep resistance and reduced gamma 1 to beta 1 phase transformation, and that gamma 2 did not appear again in high copper or palladium-enriched amalgam up to one year.

Corrosion↗
PubMed1987

Microscopy and X-ray microanalysis of subcutaneously implanted conventional and high-copper dental amalgam powders in the guinea pig.

With each material, there was only a mild early inflammatory response; particles were taken up by macrophages and giant cells. By 1.5 to 3 months, chronic granulomas had developed. With conventional amalgam, there were early changes in the intracellular material, associated with the rapid degradation of Sn-Hg particles, corresponding to the gamma 2 phase. Thereafter, intracellular particles from both types of amalgam underwent progressive degradation, producing halos of secondary material containing Ag and S. Apart from an initial loss of Cu and Sn from some high-Cu amalgam particles, there were no qualitative differences in the later changes between the two materials, although conventional amalgam particles appeared to degrade faster. With both, vast numbers of fine secondary particles containing Ag and S became widely distributed throughout the lesions and gave rise to macroscopic tattooing of the skin. Secondary material and small degrading primary particles from both types of amalgam were detected in the submandibular lymph nodes where they caused localized staining.

Animals↗
PubMed1997

Changes in surface levels of mercury, silver, tin, and copper of dental amalgam treated with carbamide peroxide and hydrogen peroxide in vitro.

OBJECTIVES: The effect of 10% carbamide peroxide or 10% hydrogen peroxide on the surface levels of mercury, silver, tin, and copper of amalgam fillings was tested in vitro with scanning electron microscopy and energy dispersive spectrometric microanalysis. STUDY DESIGN: Samples of amalgam were treated for 14 and 28 days with either 10% carbamide peroxide or 10% hydrogen peroxide solutions and compared with phosphate buffer controls. RESULTS: A significant increase in mercury levels occurred after treatment with carbamide peroxide for 14 days (p < 0.01) and 28 days (p < 0.001) and after treatment with hydrogen peroxide for 28 days (p < 0.001). A significant increase in silver levels occurred after treatment with carbamide peroxide for 14 days (p < 0.05) and 28 days (p < 0.01) and subsequent to treatment with hydrogen peroxide for 14 days (p < 0.05) and 28 days (p < 0.001). A significant reduction in tin levels occurred after treatment with hydrogen peroxide for 14 days (p < 0.01) and 28 days (p < 0.001), and after treatment with carbamide peroxide for 28 days (p < 0.01). A significant reduction in copper levels was found after treatment with carbamide peroxide for 14 days (p < 0.05). CONCLUSIONS: It appears that prolonged treatment with bleaching agents may cause microstructural changes in amalgam surfaces, possibly increasing exposure of patients to toxic byproducts.

Carbamide Peroxide↗
PubMed1996

A case of high mercury exposure from dental amalgam.

This report describes a patient who suffered from several complaints, which by herself were attributed to her amalgam fillings. Analysis of mercury in plasma and urine showed unexpectedly high concentrations, 63 and 223 nmol/l, respectively. Following removal of the amalgam fillings, the urinary excretion of mercury became gradually normalized, and her symptoms declined.

Abdominal Pain↗
PubMed1976

Recent developments in alloys for dental amalgams: their properties and proper use.

Since the development more than ten years ago of a new type of amalgam alloy that will react with mercury without forming the unfavourable gamma2 (Sn7-8Hg) phase, several new alloy brands with a similar reaction pattern have been presented. This new generation of amalgam alloy is called non-gamma2 alloy as distinct from the conventional alloys. Three of the new alloys studied contain approximately three volume percent gamma2 and should be classified as modified concentional amalgams. The non-gamma2 amalgams may be characterized in the following way: (1) instead of gamma2 they contain a reaction product of copper and tin (Cu6Sn5), the so-called eta1 phase. (2) They are significantly more resistant to corrosion than the conventional amalgams but do in time produce sufficient solid corrosion products to seal the micro-fissures between filling and cavity walls. (3) When corroding, they do not release metallic mercury, and the solid corrosion products formed and precipitated on the free surface of the fillings seem relatively little resistant to the organic acids of the plaque. (4) Most of them have relatively low creep and tensile strength, but high compressive strength. (5) Clinically the non-gamma2 amalgams are remarkable for superior marginal integrity and, seemingly, also for improved persistence of surface lustre.

Copper↗
PubMedDate not supplied

In vivo and in vitro corrosion products of dental amalgam.

Corrosion products of amalgam produced in Ringer's solution were compared with products formed in vivo using scanning electron microscopy, X-ray microanalysis, and potentiostatic anodic polarization. The corrosion products in an old amalgam were probably a mixture of tin-oxide and tin oxychloride. In vitro corrosion of fresh amalgam resulted in the buildup of similar products.

Adult↗
PubMed1991

Dental amalgam. II: Exposure to mercury.

The intraoral mercury concentration as well as the concentration in the expiratory air and in the saliva of patients with amalgams is higher than that of patients with no amalgam fillings. Test persons with amalgam fillings do not show significantly higher mercury values than test persons without amalgam fillings. However, the urine of persons who are exposed to mercury at work contains more mercury than that of people who are not.

Dental Amalgam↗
PubMed1979

Linear dimensional change of copper-rich dental amalgam.

Copper-rich amalgams made from alloy mixtures have large expansions in air at 105 +/- 2 weeks that range from 100 to 194 micrometers/cm at 60 C, from 36 to 101 micrometers/cm at 37 C, and from 14 to 44 micrometers/cm at 23 C on unrestricted 8- x 4-mm cylinders (Dispersalloy, Micro II, and Optaloy II). Other copper-rich amalgams made from one alloy usually had a slight shrinkages at the three temperatures with an exception, a slight expansion of 12 micrometers/cm at 60 C (Aristaloy CR, Indilogy non-zinc, Sybraloy, and Tytin). Dimensional changes during hardening ranged,on the average, from -3 to +19 micrometers/cm when measured by ADA Specification methods and from -2 to +25 micrometers/cm when measured by an indirect method. The clinical significance of the foregoing findings is unknown; nor is a relationship known among dimensional change of unrestricted specimens, dimensional change of restricted specimens, creep value, and clinical behavior of amalgams generally. In specific instances, however, a relationship is sometimes shown.

Chemical Phenomena↗
PubMed1999

Effect of particle configuration on structure and properties of dispersed Pd-containing dental amalgam.

The present work investigates the effect of particle configuration on the structure and properties of four dispersed type Pd-containing amalgams with the same chemical composition. The results indicate that particle configuration plays an important role not only in the structure and chemistry, but also in such properties as compressive strength, creep and mercury release rate. Compromises among the various properties of the present Pd amalgams are needed, when a decision on particle configuration is to be made. As mechanical properties or corrosion resistance is concerned, the amalgam should comprise at least one spherical alloy (matrix or dispersant). As far as mercury release is concerned, the amalgam should comprise irregular dispersant alloy. The amalgam fabricated from irregular dispersant and spherical matrix particles seems to serve all well.

Compressive Strength↗
PubMedDate not supplied

Dental amalgam, low-dose exposure to mercury, and urinary proteins in young Swedish men.

Chronic exposure to inorganic mercury can cause kidney injury. Evidence gained from occupational medicine indicates that individuals who are exposed to only environmental sources, including amalgam tooth fillings, are at very little risk. Animal experiments, however, have revealed glomerular lesions of immunologic origin after low-dose exposure to inorganic mercury. In this study, the association between the number of amalgam tooth surfaces, urinary mercury, and proteinuria was explored in a sample of 48 randomly selected, apparently healthy male students who were 17-22 y of age. Presence of any of the following proteins in two separate urine samples was considered to be potentially indicative of any tubular and/or glomerular lesion: albumin, alpha-1-microglobulin (HC-protein), kappa and lambda light chains, and N-acetyl-beta-D-glucosaminidase. No significant relationship was found between any of the proteins and amalgam or urinary mercury. The results of this study did not suggest that amalgam fillings cause kidney dysfunction in humans.

Adolescent↗
PubMed1985

Man's mercury loading from a dental amalgam.

The release of mercury from an amalgam surface in natural saliva during cyclic loading, as well as under static conditions, simulating the clinical conditions of chewing and rest, has been studied using a nuclear tracer technique. Cyclic loading strongly promoted degradation of the amalgam surface in the saliva environment. Corrosion products were found to be loosely bound on the amalgam surface and could be removed by brushing similar to toothbrushing. Most of the mercury released from the surface was present in amalgam particles, produced during the cyclic loading procedure. The daily release of ionic mercury was estimated to be approximately 3 micrograms/cm2, according to the model experiment. Extrapolating the present findings to clinical conditions, man's ionic mercury intake from dental restorations may be at the same level as the total mercury intake from food and drink.

Dental Amalgam↗
PubMed1983

A scanning transmission electron microscopy study of two dental amalgams.

Two fully aged amalgam alloys were examined using a scanning transmission electron microscope both in the transmission and scanning mode. The dispersed type amalgam containing a distribution of silver-copper spheres in addition to the Ag3Sn powder showed a markedly reduced gamma 1 grain size compared to a conventional Ag3Sn type amalgam. It is suggested that the increased compressive creep strength of the dispersed type material is a direct result of the reduced gamma 1 grain size and not due to a dispersion hardening effect from the cores of the remaining Ag-Cu spheres. Similarly, the formation of complex Cu-Sn intermediate phases at the Ag-Cu sphere surfaces are unlikely to lead to a dispersion strengthening effect. It is postulated that the reduced grain size in high copper amalgams is a consequence of the enhanced nucleating effect of a copper based phase on gamma 1.

Biomechanical Phenomena↗
PubMed1984

The effect of exposure conditions upon the release of soluble copper and tin from dental amalgams.

The concentrations of soluble copper and tin which were generated by the corrosion of a number of different amalgams in both an artificial saliva and Ringer's solution are reported. Besides variations in solution composition, the effects of solution agitation and abrasive particle wear upon the release of soluble species are studied. Immersion only, moderate solution agitation, vigorous solution agitation with abrasive particle wear, and accelerated corrosion by both constant currents and cyclic voltammetry are included. The results indicate that an artificial saliva but not Ringer's solution is capable of generating high levels of soluble tin. With artificial saliva, agitation increases the amalgam weight losses and increases soluble copper and tin concentrations, whereas agitation with Ringer's solution decreases sample weight losses and decreases levels of soluble copper and tin. This latter effect is believed to be due to the increased oxygen supply to the amalgam surfaces with agitation and the greater ability for producing protective passivating films of the basic hydroxide and copper chlorides in solutions of higher chloride ion concentrations e.g. Ringer's solution. Abrasive particle wear, including pumice, alumina, glass beads, and silica gel had varied effects upon the release of soluble species. Depending upon the amalgam, the solution, and the abrasive combination, either larger increases in copper or in tin occurred or reduced concentrations.

Copper↗