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PubMed2005

Dental amalgam restorations: daily mercury dose and biocompatibility.

Over the past 150 years, silver-tin-copper amalgam has been the most frequently used dental restorative material. Amalgam may be the single most frequently used implant material. In the early 1980s, researchers discovered that amalgam restorations release mercury vapor during chewing. This review describes the research that has led to an estimate of the daily dose of mercury that will be absorbed by a subject with a large number of amalgam restorations. Along the way, the history and chemistry of dental amalgam are outlined. The routes of absorption of liquid mercury, ionic mercury, organic mercury, and mercury vapor are also briefly described. The daily dose is found to be 14% of the threshold above which observable adverse neurological symptoms are expected. The review concludes with a summary of the research on the adverse effects of dental amalgam. As expected from the low daily dose, few adverse neurological symptoms have been reported. There is also little evidence of an association of amalgam restorations with neurodegenerative diseases, altered renal function, adverse pregnancy outcomes, or autoimmune diseases. There is a lack of data on neurobiological and neurodevelopmental effects on children who may be exposed to mercury from maternal amalgam restorations during gestation. Additional data on the role of amalgam, if any, in Alzheimers disease and multiple sclerosis are needed.

Biocompatible Materials↗

PubMed1983

Phenomenological model of creep of dental amalgam.

Earlier work revealed that creep of a particular dental amalgam can be described by the model F(t) = F0 exp (t/t0)m. Here F(t) is the creep compliance at time t, whereas F0, t0 and m are constants of the model. In the previous study only three alloys were used. It was the aim of this study to investigate the factor alloy more thoroughly. After specimen preparation, the nineteen different amalgams were aged at 37 degrees C for either one day or one week. Then creep was determined at a temperature of 22.5 degrees C and a compressive stress of 117 MN/m2. F0 turns out to depend upon both the ageing time as well as on the choice of the alloy. As expected, t0 shows up substantial differences between the respective amalgams, whereas the differences between the two ageing are absent or relatively small. The factor alloy significantly influences m. However, the ageing time exerts no significant influence upon m.

Chemical Phenomena↗

PubMed1993

The effect of the electrode potential on the release of mercury from dental amalgam.

The effect of the electrode potential on the rate of mercury dissolution from the matrix phase (gamma 1) of dental amalgam was investigated. Specimens of the Ag-Hg phase, with and without dissolved tin, were exposed to synthetic saliva and maintained at various potentials by means of a potentiostat. The amount of dissolved mercury was determined after 24 h by cold-vapor Atomic Absorption Spectrophotometry. Anodic polarization curves for the gamma 1 specimens and pure silver and mercury were also recorded. The results for the Ag-Hg phase showed a potential-independent dissolution rate between -0.6 and -0.1 V (SCE), followed by a sharp increase. Mercury dissolution from the Ag-Hg-Sn phase was much slower than from the tin-free gamma 1 phase, and potential-independent to +0.05 V (SCE); a sharp increase in mercury dissolution was observed at +0.1 V (SCE). The anodic polarization curves for the Ag-Hg-Sn phase indicated passivity between -0.67 V and +0.1 V (SCE), but no clear passivation for the Ag-Hg specimen, silver, or mercury. The results show that in the potential-independent region, mercury dissolved in the atomic form from both the tin-free and tin-containing gamma 1 phase. The increase in dissolution in the upper range of potentials was tentatively attributed to selective anodic dissolution of silver and an onset of electrochemical dissolution. The results indicate that the rate of mercury release from the gamma 1 phase of dental amalgam was not affected by potential changes due to alloying or galvanic contacts unless the potential exceeded some critical value.

Dental Amalgam↗

PubMed1998

Dental amalgam: update on safety concerns. ADA council on Scientific Affairs.

This report of the Council on Scientific Affairs reviews and discusses recent studies concerning the safety of dental amalgam, with an emphasis on studies that have been published since the 1993 review of dental amalgam by the U.S. Public Health Service Committee to Coordinate Environmental Health and Related Programs. The Council concludes that, based on currently available scientific information, amalgam continues to be a safe and effective restorative material.

Air Pollution, Indoor↗

PubMed2002

Mercury distribution and concentration in rats fed powdered dental amalgam.

The aim was to evaluate the distribution and elimination of mercury in the tissues of rats exposed to powdered dental amalgam. The study comprised of three groups: the first (A) was an unexposed control, the second (B) was fed 8.3mg of powdered amalgam weekly for 12 weeks, and the third (C) was fed 25.0mg of powdered amalgam weekly for 4 weeks followed by either a 4- or 8-week period of non-exposure. The total amount of amalgam administered in each of the latter two groups was 0.1g. Animals were killed at 4, 8 and 12 weeks, and their kidneys, liver and brains were removed. Mercury present in tissues from one side was analysed by cold-vapour atomic absorption spectrometry; tissues from the other side were stained autometallographically. No mercury was detected in any tissue of control group A. In group B, the mercury concentration in the kidneys was significantly higher than that of the control, whereas in group C, the mercury concentration in both the liver and kidneys decreased significantly during the period of non-exposure. Mercury was not detected in brain tissue from any group. The light-microscopic findings were in agreement with the quantitative results. Mercury grains were most common in the renal cortex, especially in the proximal tubule. Although there was some mercury accumulation in the tissues of the two experimental groups, no pathological reactions were noted. These data suggest that, in the rat, the ingestion of dental amalgam in small quantities for a limited period does not lead to morphological changes in the liver, brain or kidneys. It seems likely that mercury does not accumulate in brain tissue and that any accumulation in the kidneys and liver is at least partially reduced after ingestion ceases.

Animal Feed↗

PubMed1985

The response of dental amalgam to dynamic loading.

A conventional (gamma 2-containing) dental amalgam was fatigue-tested at 1800 and 80 cycles/min, employing uni-axial, sinusoidal loading, with R = -8. Compressive, tensile, and creep tests were conducted to characterize the alloy's static mechanical behavior. Tests were performed at 37 degrees C on specimens which were aged for seven days, at 37 degrees C. Fatigue-tested specimens were microscopically examined for fracture surface appearance and crack path. The amalgam demonstrated a frequency dependence and a significant reduction in fracture strength due to fatigue loading. The fatigue crack path was primarily intergranular in the gamma 1 phase and inclined at approximately 45 degrees to the principal stress axis. These observations are characteristic of some metals when subjected to low-frequency, elevated temperature testing where significant grain boundary sliding occurs, and therefore suggest a creep-fatigue interaction for this alloy.

Dental Amalgam↗

PubMed1971

[Condensation of dental amalgam].

Explore the source record for details and available documents.

Dental Amalgam↗

PubMed1998

Mercury in human colostrum and early breast milk. Its dependence on dental amalgam and other factors.

The mercury concentration in 70 breast milk samples (Hg-M) from 46 mothers, collected within the first 7 days after delivery, was determined by cold vapour atomic absorption spectrometry. For comparison, 9 formula milk samples (reconstituted with Hg-free water) were investigated. The Hg-M in the human milk samples ranged from < 0.2 to 6.86 micrograms/L (median 0.37), in the formula milk samples from 0.4 to 2.5 micrograms/L (median 0.76). The Hg-M in the breast milk samples correlates positively with the number of maternal teeth with dental amalgam. The mean Hg-M of amalgam-free mothers was < 0.2 microgram/L, while milk from mothers with 1-4 amalgam fillings contained 0.57 microgram/L, with 5-7 fillings 0.50 microgram/L and with more than 7 fillings 2.11 micrograms/L. Hg-M correlated negatively to the day after delivery. Frequency of fish consumption tends to influence Hg-M positively, while the age of the mother shows no significant correlation. In the first 2 to 3 days after delivery some colostrum samples with Hg-M higher than in formula milk were found. Later on, the Hg-concentration in the breast milk was equal or even lower to that in formula milk. The higher Hg burden of infants' tissues from mothers with dental amalgam, as reported previously, must be explained (1) by a prenatal transfer of Hg from the mother's fillings through the placenta to the fetus, followed by a redistribution of this Hg in the body of the newborn, and (2) an additional burden via breast milk. Nevertheless, the comparison of Hg-M in breast and formula milk, the relatively moderate Hg burden in both kinds of milk, and the multiple manifest advantages of breast feeding speak against any limitation of nursing, even for mothers with a large number of dental amalgam fillings.

Adult↗

PubMed1982

The creep compliance of dental amalgam in the stress range of 20-80 MPa.

The continuous compressive creep curves of four distinct types of one-week-old dental amalgam were monitored for one day on a specially designed mini-specimen creep apparatus. Creep conditions included three different applied constant stress levels (20, 40, and 80 MPa), and temperatures ranging from 0 degrees C to 60 degrees C. To compensate for changing dimensions at high creep strains, the data was converted to terms of compressive creep compliance. For all types of dental amalgam, compressive creep increased both with increased applied stress and with increased test temperature. The two high copper systems evaluated appear to approach a steady-state creep condition up to the highest temperatures tested, but the two conventional amalgams appear to change their creep exponent precipitously at temperatures above 45 degrees C.

Dental Amalgam↗

PubMed2003