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PubMedDate not supplied

The effect of bleaching agents on mercury release from spherical dental amalgam.

To investigate the effect of carbamide peroxide, hydrogen peroxide, and over-the-counter home bleaching products on the release of mercury from spherical dental amalgam, 150 uniform amalgam specimens were prepared in clear acrylic blocks, aged for one week at 37 degrees C, and placed into individual polystyrene jars containing 20 mL of sterile saline. The specimens were divided into three groups of 50 and bleached in eight-hour cycles. All groups exposed to bleach showed increased mercury release over time.

Analysis of Variance↗

PubMed1984

Microprobe analysis of dental amalgam alloy particles of Ag-Cu eutectic composition.

An electron microprobe was used to investigate the composition and microstructure of commercially available, and experimental dental amalgam alloy particles of approximately Ag-Cu eutectic composition. The method of alloy and amalgam specimen preparation and the technique used in microprobe analysis have been briefly outlined. The dispersant particles in one commercial alloy were of Ag-Cu eutectic composition (28.1% Cu), in another commercial alloy they were Cu-rich (31% Cu). Although the dispersant particles were predominantly of uniform appearance, there was evidence in some particles of an internal structure pattern, small spherical inclusions or voids. The possible composition of the Cu-rich inclusions was investigated using particles from an experimental alloy of approximately Ag-Cu eutectic composition.

Chemical Phenomena↗

PubMed1997

The high-copper dental amalgam alloys.

For many years, the amalgamation of silver with mercury to produce a condensable mixture which could be used to restore carious defects in teeth followed a tortuous path of negative results. However, at the turn of the century, amalgam alloys having acceptable characteristics for successful clinical use emerged. From that point on, silver amalgam was widely accepted as the material of choice for low-cost, easily placed, and durable restorations. About 60 years later, a major discovery occurred that resulted in a most significant improvement in the clinical performance of this material. The key to this improvement was an increase in the Cu content of the amalgam alloy which previously had been considered to be inappropriate. This paper describes the history of this discovery, which produced what has come to be known as high-copper dental amalgam alloys.

Canada↗

PubMed1997

The effect of tin in the Ag-Hg phase of dental amalgam on dissolution of mercury.

OBJECTIVES: The aim of this study was to determine the relationship between the tin content in the gamma 1 phase of dental amalgam and the kinetics of mercury dissolution. METHODS: The tested materials were the same eleven commercial amalgams used by Mahler et al. (1994) to study mercury evaporation, which contained from 0.13% to 2.49% Sn in the gamma 1. In one set of tests, specimens were stabilized in air before exposure to synthetic saliva for three 24 h sampling periods. In another set of tests, they were exposed for 2 h immediately after wet-grinding. Solutions were analyzed for mercury by atomic absorption spectrophotometry. The results were analyzed by ANOVA and Turkey tests (p < 0.05). RESULTS: For air-stabilized specimens, the 24 h Hg loss was independent of the tin content in gamma 1 for 0.92 to 2.49% Sn. The loss was higher for amalgams containing 0.13% and 0.32% Sn. For abraded specimens, the 2 h Hg loss decreased with increasing tin content in gamma 1. It is proposed that tin oxide growth is initially controlled by diffusion of tin to the gamma 1/tin oxide interface, the rate of which increases with increasing Sn content in gamma 1. Later the growth becomes controlled by the electric field across the oxide. Mercury release rate, controlled by diffusion through the oxide, is inversely proportional to the oxide thickness and initially lower for high Sn content in gamma 1. For a steady state oxide thickness, tin diffusion and tin content in gamma 1 no longer affect mercury dissolution. When tin oxide film dissolves, a minimum tin content is required to maintain a barrier against mercury dissolution. SIGNIFICANCE: The results show the importance of rapid formation of a surface oxide to minimize mercury dissolution. The theoretical analysis provides a quantitative model for explanation of the effects of tin content and time.

Analysis of Variance↗

PubMed1986

In vitro testing of dental materials by means of macrophage cultures: II. Effects of particulate dental amalgams and their constituent phases on cultured macrophages.

It is known that macrophages play an important role in the removal of foreign particulate matter from tissue. When powdered dental amalgam is introduced into the soft tissues an amalgam tattoo is formed due to the intracellular degradation of amalgam by macrophages and their polykaryons. It was therefore feasible to study the effects of particulate amalgams as well as their individual phases on macrophages in vitro. The parameters compared were rate of the phagocytosis, changes of cellular morphology, and release of lactate dehydrogenase (LDH) to demonstrate plasma membrane permeability. It was shown that all the alloys except the Sn8Hg particles (gamma 2-phase) and gamma 2-containing Revalloy were effectively phagocytized by macrophages, and the alterations in cellular morphology were slight during the first day. Prominent cellular damage was seen in cultures treated with particulate Ag2Hg3 (gamma 1-phase) and Revalloy for 1 week. A slight increase in LDH activity in the medium was seen one hour after the alloy treatment. The LDH activities due to the amalgam treatment increased in the order Dispersalloy less than Revalloy less than Sybraloy. Intraperitoneal phagocytosis did not cause any morphological changes in macrophages, but the per cent of phagocytosis was diminished.

Animals↗

PubMed1988