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PubMed1981

[Solubility of metal components into tissue culture medium from dental amalgams (author's transl)].

Solubility of metal components into tissue culture medium, YLH, from various dental amalgams including high copper, conventional and copper amalgam was measured with atomic absorption spectrometry. The results obtained were as follows.: 1. Mercury solubility was found much in all the dental amalgams after one day extraction. This was followed by gradual increase in solubility in the high copper amalgams until after seven days. On the otherhand, initial high solubility was maintained in conventional and copper amalgams through the whole experimental period. 2. Higher solubility of silver and copper was recorded in the high copper amalgams. 3. Zinc was only found in Dispersalloy and copper amalgam. 4. Tin was unable to be measured in all the amalgams examined. It was considered that the present results could shed a light on the mechanism for cytotoxicity yielding of the dental amalgams.

Culture Media↗

PubMed1996

Equilibrium vapor pressure of mercury from dental amalgam in vitro.

OBJECTIVES: The purpose of this study was to acquire reliable quantitative data on mercury vapor pressure above the surface of dental amalgam samples in both the as-formed and the abraded state. METHODS: The equilibrium vapor pressure of mercury from dental amalgam was obtained using residual gas analysis in conjunction with a quartz crystal microbalance. The measurements were performed under ultrahigh-vacuum conditions. RESULTS: Using the residual gas analyzer, the average mercury vapor pressures measured from the as-formed and abraded dental amalgam surfaces were 8 x 10(-7) and 1.7 x 10(-4) Pa, respectively. The corresponding vapor densities are: 6 x 10(-2) micrograms/m3 and 14 micrograms/m3. The average mercury vapor pressures measured from the as-formed and abraded dental amalgam surfaces using the quartz crystal microbalance were: 2.4 x 10(-6) and 1.0 x 10(-4) Pa, respectively. The corresponding vapor densities are: 0.2 microgram/m3 and 8 micrograms/m3. SIGNIFICANCE: This project provides a measurement of the equilibrium vapor pressure of mercury from as-formed and abraded amalgam surfaces. By definition, the equilibrium vapor pressure provides the maximum density of mercury which can be present in the environment above the amalgam. The vapor density of mercury within the oral cavity must be less than this value due to the dynamic nature of the system.

Chemical Phenomena↗

PubMed1989

Dental amalgam: a review of the literature.

Since the 1800s, dental amalgam has been the most commonly used dental restorative material. Each year, dentistry in the United States uses over 100 tons of mercury, continuing a controversy regarding mercury's safety for patients and dental personnel.

Dental Amalgam↗

PubMed2002

Nordic dentists' knowledge and attitudes on dental amalgam from health and environmental perspectives.

The aim of this study was to identify differences and similarities between the Nordic countries in dentists' use of dental amalgam as a restorative material, and also their knowledge and attitudes about amalgam from health, environmental, ethical, economic and social points of view. Procedures for handling amalgam waste were also studied. A random sample of 250 dentists was drawn from the national registers of authorized dentists in each country in late autumn 1997. At the beginning of 1998, a questionnaire was sent to all the dentists in the study group. The response rate was 77.6% in Denmark, 73.2% in Finland, 78.8% in Norway, and 84.0% in Sweden. In Finland and Sweden the use of dental amalgam had almost ceased, particularly for younger patients, while in Norway and especially in Denmark it was still widely used. Dentists' knowledge of the environmental effects of amalgam was confused, but most dentists had installed amalgam separators in their dental units by 1998. The majority of dentists in each country wanted to keep dental amalgam as a restorative material even in the future, and they did not want to ban the import of mercury to their home countries. Most dentists considered amalgam to be a health risk for at least some patients, and a great majority (from 76% in Sweden to 94% in Norway) considered composite as a possible odontological risk to patients. Since a majority of the dentists considered both amalgam and composites possibly harmful to patients, efforts to develop better alternatives to amalgam should continue.

Adult↗

PubMed2002

Dental amalgam affects urinary selenium excretion.

Selenium may have a protective effect against mercury toxicity. The aim of the present study was to investigate if selenium excretion in urine was affected in persons with dental amalgam fillings. The reason for this study is that dental amalgam is the most important source of inorganic mercury exposure in the general population, although the potential toxic effects of this exposure remain a subject for debate. The chelating agent 2,3 dimercaptopropane-1-sulfonate (DMPS) was injected intravenously (2 mg/kg) to provoke metal excretion. Urine samples were subsequently collected at intervals over a 24-h period. Selenium concentration was determined by hydride-generation atomic absorption spectrometry. The study was comprised of 20 persons who claimed symptoms from dental amalgam and 21 healthy persons with amalgam fillings. There were two control groups without amalgam. One control group had amalgam replaced because of concern about illness resulting from mercury release (n = 20), whereas the other control group never had amalgam (n = 19). Individuals with amalgam excreted less selenium (36.4 microg, median value) over 24 hours than those without amalgam (47.5 microg) (p = 0.016). There was no difference in selenium excretion between groups with (42.4 microg) and without (39.4 microg) amalgam-related symptoms (p = 0.15). The findings indicate that individuals exposed to low levels of elemental mercury from dental amalgam excrete less selenium to urine than unexposed individuals.

Case-Control Studies↗

PubMed1994

A method of determining the corrosive properties of dental amalgams.

The purpose of this study was to determine the corrosive properties of 5 dental amalgams, using a modified rotating disk electrode method described by Van der Merwe, De Wet and Mc Crindle (1991). Ten cylindrical specimens of each amalgams were prepared according to the ISO guidelines. The amount of gamma-2 present was determined by the method employed by Sarkar and Greener (1972), while the corrosion rates were calculated from the Tafel slopes of the polarisation diagrams. All data were analysed statistically. Results showed that at day one Silvalloy contained the most gamma-2, followed by Amalgaphase (previous formulation) and Amalgaphase (new formulation). Dispersalloy and Amalga Sphere contained no gamma-2 at day one. At day nine none of the amalgams tested contained gamma-2 phase. The corrosion rates of the different groups of amalgam varied significantly (p < 0.01) as tested by ANOVA. The spherical amalgam, Amalga Sphere, showed a better corrosion resistance (p < 0.01) than the other amalgams. The method used for evaluating the corrosive properties of dental amalgam proved to be precise, rapid and simple.

Analysis of Variance↗

PubMed2005

Mercury recovery in situ of four different dental amalgam separators.

Amalgam separators are used to physically remove dental amalgam from waste water in dental clinics. They are thereby supposed to reduce mercury (Hg) emissions to the municipal waste water system to acceptable levels. We here present results from a comparative study in situ of three amalgam separators available on the market, all with a claimed efficiency of 99% according to Danish and ISO protocols, and using sedimentation as the principle of separation. We also present corresponding data for an investigational prototype of an improved separator. The obtained efficiency of the three commercial separators is far below what is stated by the manufacturer and by authorities assumed to be the efficiency in clinical conditions. They reduced Hg emissions by 79 - 91%, leaving an average Hg content in outgoing waste water of 1.5 mg L(-1). However, the prototype separator participating in this study retained 99.9% of the waste water Hg emissions, leaving an average Hg content in outgoing waste water of 0.004 mg L(-1). Physical restrictions prohibit sedimentary type separators to recover the Hg fractions causing the largest damages in wastewater treatment plants. This fraction is not considered in the ISO protocol for testing amalgam separators, which therefore needs to be revised. Abolishing the use of dental amalgam and cleaning the tubing systems is the most efficient long-term solution to reduce Hg emissions from dental clinics. Until then, Hg emissions originating from placing, polishing or removing existing amalgam fillings, should be counteracted by the use of low-emission amalgam separators, already on the market or presently being developed for use alone or together with sedimentary type amalgam separators.

Dental Amalgam↗

PubMed1988

Sn in the Ag-Hg phase of dental amalgam.

In a recent study, Sarkar and Eyer (1986) studied an amalgam which was formed using a unique procedure. Based on their results, they concluded that the solubility of Sn in the Ag-Hg (gamma 1) phase of dental amalgam was virtually nil (less than 0.25 wt%). This finding is contrary to the published results of other investigations. The purpose of the present study was to clarify these disparate findings. A low-copper dental amalgam was examined by electron probe microanalysis. This amalgam was selected because it exhibits unusually large gamma 1 grains (10 microns). Because the influence of the electron-analyzing beam can be completely contained within these large grains, grain boundaries or peripheral phases would not be excited, and a valid analysis of the gamma 1 grains themselves could be made. The analyses showed significant Sn contents of 2.0-3.0 wt%. Analyses of areas which contained grain boundaries showed slight or no differences in Sn content compared with that for the grains alone. Furthermore, secondary electron scans of this dental amalgam failed to reveal the intergranular precipitates of Sn-Hg observed by Sarkar and Eyer (1986) in their amalgam. These different results can be explained by the fact that the unique amalgam investigated by Sarkar and Eyer does not exhibit the same diffusional patterns as does dental amalgam, and that the composition of the gamma 1 in the two amalgams is not the same. The final conclusion is that the Ag-Hg (gamma 1) phase in dental amalgam does indeed contain a significant amount of Sn.

Dental Amalgam↗

PubMed1979

A method for the measurement of dimensional change of dental amalgam.

A dimensional change occurs during the setting of a dental amalgam. A measurement circuit, which makes it possible to register these changes, is introduced. To this purpose strain gages were used. The registration instrument is tested by comparing different dental amalgam products.

Chemical Phenomena↗

PubMed2002

Issues in design and analysis of a randomized clinical trial to assess the safety of dental amalgam restorations in children.

The Casa Pia Study of the Health Effects of Dental Amalgams in Children is a randomized clinical trial designed to assess the safety of low-level mercury exposure from dental amalgam restorations in children. It is being carried out in 507 students (8 to 12 years of age at enrollment) of the Casa Pia school system in Lisbon, Portugal, by an interdisciplinary collaborative research team from the University of Washington (Seattle) and the University of Lisbon, with funding from the National Institute of Dental and Craniofacial Research. Since the goal of the trial is to assess the safety of a treatment currently in use, rather than the efficacy of an experimental treatment, unique design issues come into play. The requirements to identify as participants children who have extensive unmet dental treatment needs and who can be followed for 7 years after initial treatment are somewhat in conflict, since those with the most treatment needs are usually in lower socioeconomic categories and more difficult to track. The identification of a primary study outcome measure around which to design the trial is problematic, since there is little evidence to indicate how health effects from such low-level exposure would be manifested. The solution involves the use of multiple outcomes. Since there are concerns about safety, multiple interim comparisons over time between treatment groups are called for which, in conjunction with the use of multiple outcomes, require an extension of statistical methodology to meet this requirement. Ethical questions that have to be addressed include whether assent of the children participating is required or appropriate, and whether the director of the school system, who is the legal guardian for approximately 20% of the students who are wards of the state and live in school residences, should provide consent for such a large number of children. Approaches taken to address these and other design issues are described.

Child↗

PubMed1982

Tensile creep of dental amalgam.

Rather than the usual compressive dental creep, various types of one week old dental amalgams were continuously monitored in tensile creep. Testing was done at 37, 45 and 50 degrees C, in a specially designed apparatus capable of 0 to 60 degrees C while maintaining a constant true tensile stress of 17 MPa. For the first time, the classical four stages of creep were observed at elevated temperatures in the low Cu amalgams, including creep rupture. The high Cu systems displayed only transient creep up to 50 degrees C and no rupture. Approximately one half the stress was needed in tension to provide the equivalent creep in compression.

Copper↗

PubMed1976

The effect of anodic polarization on the tensile strength of dental amalgam.

The effect of corrosion upon dental amalgam was studied by measuring the effect of anodic polarization on its tensile strength. A conventional tensile testing method using dumb-bell shaped specimens deformed along the long axis was employed. The results showed a significant reduction (27%) in the mean tensile strength, due to the anodic polarization of conventional amalgam, whereas the strength of the high Cu-containing Dispersalloy amalgam was unaffected by polarization. When the diametral tensile strengths of polarized and unpolarized conventional amalgam and Dispersalloy specimens were compared (ADA Specification No. 1), no significant difference in strength was observed. These results indicate that the anodic corrosion of gamma2 phase network in the conventional amalgam fillings can be directly attributed to a reduction of tensile strength which would be manifested clinically as marginal breakdown. It appears also that the diametral tensile test is not sufficiently discriminating to allow for an in vitro simulation of clinical properties.

Copper↗

PubMed1975

Creep of dental amalgam.

The steady-state creep rates of dental amalgams were measured and the creep rates were correlated with the microstructure of the amalgams. The influence of manipulation variables on creep rate and microstructure are evaluated. The samples were either mechanically or hand triturated, hand condensed, and stored at 20 degrees C for 7 d. The specimens were subjected to a constant tensile load for 24 h, and the elongation was measured with a displacement transducer. The smallest creep rate was found on a spherical amalgam, and the highest on an amalgam made from a preamalgamated fine grain alloy. A correlation between microstructure and creep rate could be demonstrated. The amount of gamma2 phase did not seem to influence the creep rate. Amalgams that had large closely packed gamma particles surrounded by a small volume fraction of gamma1 phase exhibited a low creep rate. Amalgams that had small broken up gamma particles surrounded by a large volume fraction of gamma1 exhibited a high creep rate. Abusive manipulation of lathe-cut amalgam alloys resulted in high creep rates, small broken up gamma particles and a high volume fraction of gamma1.

Dental Alloys↗

PubMed1975

Electrochemical properties of copper and gold containing dental amalgams.

Alloying or admixing of a dental amalgam alloy with an element or alloy which has a higher affinity for tin offers a means for eliminating the corrosion prone gamma2 phase. Accordingly, the corrosion behaviour of non-conventional amalgams containing Cu and Au were investigated by anodic polarization studies in Ringer's solution. The Cu containing amalgams were produced by admixing Cu-Hg (copper amalgam) with conventional amalgam in the ratios of 0-5:1 and 1:1. A 10 w/o Au in Ag-3-Sn was used as the gold amalgam alloy. The anodic polarization profile of the 0-5:1 Cu admixed was similar in shape to admixed conventional amalgams although current densities were less. After ageing for 1 month the minus 250 mV peak associated with gamma2 disappeared and the current density decreased by ten fold. After 2 months the current density decreased by one hundred fold. The anodic polarization of the 1:1 Cu admixed amalgams did not display the minus 250 mV (gamma2) peak after 1 week and current densities were 10-3 below that of conventional amalgams. The behaviour of these interesting amalgams is rationalized on the basis of the ease of formation of Cu-Sn intermetallics where Cu/Sn larger than or equal to 3. The anodic polarization profile of 10 w/o Au containing amalgam essentially is that of conventional amalgam and does not change drastically after 6 months. Although the Au may reduce or eliminate the gamma2 phase the resulting AuSn4 apparently corrodes in an analogous fashion. However, since distribution of AuSn4 may be different from gamma2, i.e. not continuous, the effect of corrosion on its mechanical properties may be different.

Copper↗

PubMedDate not supplied

Release of mercury from dental amalgam and its influence on salivary antioxidant activity.

Dental amalgam fillings are known to release significant levels of mercury (Hg) in saliva which could represent a continuous source of oxidative damage to tissues. The present investigation was aimed at verifying this hypothesis by determining a possible correlation between salivary Hg levels and salivary total antioxidant activity (TAA), used as an index of oxidative stress. Samples of saliva from 34 healthy donors were analyzed for Hg content, through vapor atomic absorption spectrometry, and for TAA, by determining the ferric reducing ability ('FRAP' method). A significant correlation between Hg and the number of amalgam restorations or total amalgam surface was evident in both the male and female subjects. A significant negative correlation between TAA and Hg levels or number of amalgam restorations or amalgam surface was evident in females, indicating that small increases in salivary Hg were sufficient to produce a decrease in salivary TAA. On the other hand, no significant correlation was found in the males. The present study provides, for the first time, evidence of a pro-oxidant role of the amalgam Hg chronically released in saliva.

Adolescent↗

PubMed1987

The safe and effective use of dental amalgam.

Case reports in the lay press claim that amalgam restorations may cause a number of local and systemic symptoms. Several recent scientific reports and reviews maintain that dental amalgam is a safe and effective restorative material. The advantages of dental amalgam as a restorative material include its ease of handling, diversity in application, physical characteristics and the infrequency of local and systemic biological side effects. The disadvantages of dental amalgam comprise poor aesthetics, local degradation, occasional allergic responses to some of its components or degradation products, and the toxicity of mercury. The clinical diagnosis of secondary caries constitutes the main reason for the replacement of amalgam restorations in both dentitions. Great variations prevail with regard to the longevity of amalgam restorations. Half of the restorations replaced in permanent teeth are about 8-10 year old, but the range is from 0 to about 40 years. Restorations needing replacement in deciduous teeth are in service for shorter periods of time than those in permanent teeth. In a longitudinal study of more than 600 class II amalgam restorations in permanent teeth, only about 6 per cent were replaced after a 6-7 year observation period. The longevity of amalgam restorations depends on a number of factors, including the quality of the material, its use and manipulation by the dentists and dental assistants and possibly also the oral hygiene of the patient.

Dental Amalgam↗

PubMed1989

Status of scrap (recyclable) dental amalgams as environmental health hazards or toxic substances.

This article presents information garnered after an investigation by the Environmental Protection Agency in 1987 of dentists and others who had sold scrap dental amalgam to refiners who had "arranged for the disposal or treatment ... of hazardous substances," and were responsible for adverse consequences associated with their subsequent management and refining. Information about the health hazard status of scrap dental amalgams was obtained by: interviews with toxicologists, review of published lists of toxic and hazardous materials, and survey of biomedical publications (1977 through 1987) concerning toxicity or health hazards associated with dental amalgams. The conclusions were that scrap dental amalgam is not: a waste substance to be disposed of, but is a product of commercial value; identified or regulated by the Environmental Protection Agency, the Occupational Safety and Health Administration, the Department of Transportation, the Food and Drug Administration, the National Institute of Occupational Safety and Health, the US Public Health Service, or the Centers for Disease Control as an environmental health hazard or toxic substance; identified by toxicologists and persons responsible for solid waste regulation as a toxic substance or environmental health hazard; nor proved by scientific study to be toxic or hazardous in the manner and form in which it is collected and stored by dentists and subsequently sold to metal refiners.

American Dental Association↗

PubMed2003

Uptake and accumulation of mercury from dental amalgam in the common goldfish, Carassius auratus.

In this study, the bioavailability and accumulation of mercury from external environmental exposure to mixed, cured, milled, sieved and proportioned dental amalgam was examined in the common goldfish, Carassius auratus. Fish were exposed to dental amalgam (particle size range from < 0.10 to 3.15 mm) in order to represent the particle size and distribution of that found within the typical dental office wastewater discharge stream. Experimental amalgam water loadings were 0 g/l, 0.5 g/l and 1 g/l in glass aquaria at 15 degrees C for 28 days. Fish tissues were sampled at 5 min and 28 days of exposure, and the liver, brain, muscle and whole body analyzed for total mercury using cold vapor atomic fluorescence spectroscopy. Mercury was found in several tissues examined and generally increased with exposure to higher amounts of dental amalgam. The highest levels were found in the whole body (17.68 +/- 5.73 microg/g) followed by the liver (0.80 +/- 0.16 microg/g) and muscle (0.47 +/- 0.16 microg/g). The lowest concentrations were seen in the brain (0.28 +/- 0.19 microg/g). Compared to controls, concentrations in the whole body, muscle and liver in fish exposed for 28 days to the highest concentration of amalgam were 200-, 233-, and 40-fold higher, respectively. This study shows that mercury from an environmental exposure to representative samples of dental amalgam typically found within the dental wastewater discharge stream is bioavailable to fish and may accumulate in internal tissues.

Animals↗