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Journal ArticleDOI

The potential adverse health effects of dental amalgam.

TL;DR: This review has uncovered no convincing evidence pointing to any adverse health effects that are attributable to dental amalgam restorations besides hypersensitivity in some individuals.
Abstract: There is significant public concern about the potential health effects of exposure to mercury vapour (Hg0) released from dental amalgam restorations. The purpose of this article is to provide information about the toxicokinetics of Hg0, evaluate the findings from the recent scientific and medical literature, and identify research gaps that when filled may definitively support or refute the hypothesis that dental amalgam causes adverse health effects. Dental amalgam is a widely used restorative dental material that was introduced over 150 years ago. Most standard dental amalgam formulations contain approximately 50% elemental mercury. Experimental evidence consistently demonstrates that Hg0 is released from dental amalgam restorations and is absorbed by the human body. Numerous studies report positive correlations between the number of dental amalgam restorations or surfaces and urine mercury concentrations in non-occupationally exposed individuals. Although of public concern, it is currently unclear what adverse health effects are caused by the levels of Hg0 released from this restoration material. Historically, studies of occupationally exposed individuals have provided consistent information about the relationship between exposure to Hg0 and adverse effects reflecting both nervous system and renal dysfunction. Workers are usually exposed to substantially higher Hg0 levels than individuals with dental amalgam restorations and are typically exposed 8 hours per day for 20–30 years, whereas persons with dental amalgam restorations are exposed 24 hours per day over some portion of a lifetime. This review has uncovered no convincing evidence pointing to any adverse health effects that are attributable to dental amalgam restorations besides hypersensitivity in some individuals.
Citations
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Journal ArticleDOI
TL;DR: This review covers the toxicology of mercury and its compounds and leads to general discussion of evolutionary aspects of mercury, protective and toxic mechanisms, and ends on a note that mercury is still an “element of mystery.”
Abstract: This review covers the toxicology of mercury and its compounds. Special attention is paid to those forms of mercury of current public health concern. Human exposure to the vapor of metallic mercury dates back to antiquity but continues today in occupational settings and from dental amalgam. Health risks from methylmercury in edible tissues of fish have been the subject of several large epidemiological investigations and continue to be the subject of intense debate. Ethylmercury in the form of a preservative, thimerosal, added to certain vaccines, is the most recent form of mercury that has become a public health concern. The review leads to general discussion of evolutionary aspects of mercury, protective and toxic mechanisms, and ends on a note that mercury is still an "element of mystery."

1,953 citations

Journal ArticleDOI
TL;DR: A critical review of the literature published since January 2012 concluded that more knowledge synthesis efforts are needed to translate the research results into management tools for health professionals and policy makers.

294 citations


Cites background from "The potential adverse health effect..."

  • ...…across Europe, United States, Canada, and Australia among others have concluded that there is no strong scientific evidence to make a causal link between dental amalgam restorations and adverse health outcomes except for some rare cases of hypersensitivity in some people (Brownawell et al., 2005)....

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  • ...Expert panels from across Europe, United States, Canada, and Australia among others have concluded that there is no strong scientific evidence to make a causal link between dental amalgam restorations and adverse health outcomes except for some rare cases of hypersensitivity in some people (Brownawell et al., 2005)....

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Journal ArticleDOI
19 Apr 2006-JAMA
TL;DR: Children who received dental restorative treatment with amalgam did not, on average, have statistically significant differences in neurobehavioral assessments or in nerve conduction velocity when compared with children who received resin composite materials without amalgam.
Abstract: ContextDental (silver) amalgam is a widely used restorative material containing 50% elemental mercury that emits small amounts of mercury vapor. No randomized clinical trials have determined whether there are significant health risks associated with this low-level mercury exposure.ObjectiveTo assess the safety of dental amalgam restorations in children.DesignA randomized clinical trial in which children requiring dental restorative treatment were randomized to either amalgam for posterior restorations or resin composite instead of amalgam. Enrollment commenced February 1997, with annual follow-up for 7 years concluding in July 2005.Setting and ParticipantsA total of 507 children in Lisbon, Portugal, aged 8 to 10 years with at least 1 carious lesion on a permanent tooth, no previous exposure to amalgam, urinary mercury level <10 μg/L, blood lead level <15 μg/dL, Comprehensive Test of Nonverbal Intelligence IQ ≥67, and with no interfering health conditions.InterventionRoutine, standard-of-care dental treatment, with one group receiving amalgam restorations for posterior lesions (n = 253) and the other group receiving resin composite restorations instead of amalgam (n = 254).Main Outcome MeasuresNeurobehavioral assessments of memory, attention/concentration, and motor/visuomotor domains, as well as nerve conduction velocities.ResultsDuring the 7-year trial period, children had a mean of 18.7 tooth surfaces (median, 16) restored in the amalgam group and 21.3 (median, 18) restored in the composite group. Baseline mean creatinine-adjusted urinary mercury levels were 1.8 μg/g in the amalgam group and 1.9 μg/g in the composite group, but during follow-up were 1.0 to 1.5 μg/g higher in the amalgam group than in the composite group (P<.001). There were no statistically significant differences in measures of memory, attention, visuomotor function, or nerve conduction velocities (average z scores were very similar, near zero) for the amalgam and composite groups over all 7 years of follow-up, with no statistically significant differences observed at any time point (P values from .29 to .91). Starting at 5 years after initial treatment, the need for additional restorative treatment was approximately 50% higher in the composite group.ConclusionsIn this study, children who received dental restorative treatment with amalgam did not, on average, have statistically significant differences in neurobehavioral assessments or in nerve conduction velocity when compared with children who received resin composite materials without amalgam. These findings, combined with the trend of higher treatment need later among those receiving composite, suggest that amalgam should remain a viable dental restorative option for children.Trial Registrationclinicaltrials.gov Identifier: NCT00066118

223 citations


Cites background from "The potential adverse health effect..."

  • ...In addition to age, the inclusion criteria were (1) at least one carious lesion in a permanent tooth, (2) no previous exposure to amalgam, (3) urinary mercury level lower than 10 μg/L, (4) blood lead level lower than 15 μg/dL, 5) Comprehensive Test of Nonverbal Intelligence (CTONI) IQ of at least 67, and (6) no interfering health conditions....

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Journal ArticleDOI
TL;DR: Characteristic X‐ray fluorescence is a technique that can be used to establish elemental concentrations for a large number of different chemical elements simultaneously in different locations in cell and tissue samples to gain insight into cellular processes.
Abstract: Characteristic X-ray fluorescence is a technique that can be used to establish elemental concentrations for a large number of different chemical elements simultaneously in different locations in cell and tissue samples. Exposing the samples to an X-ray beam is the basis of X-ray fluorescence microscopy (XFM). This technique provides the excellent trace element sensitivity; and, due to the large penetration depth of hard X-rays, an opportunity to image whole cells and quantify elements on a per cell basis. Moreover, because specimens prepared for XFM do not require sectioning, they can be investigated close to their natural, hydrated state with cryogenic approaches. Until several years ago, XFM was not widely available to bio-medical communities, and rarely offered resolution better then several microns. This has changed drastically with the development of third-generation synchrotrons. Recent examples of elemental imaging of cells and tissues show the maturation of XFM imaging technique into an elegant and informative way to gain insight into cellular processes. Future developments of XFM-building of new XFM facilities with higher resolution, higher sensitivity or higher throughput will further advance studies of native elemental makeup of cells and provide the biological community including the budding area of bionanotechnology with a tool perfectly suited to monitor the distribution of metals including nanovectors and measure the results of interactions between the nanovectors and living cells and tissues.

218 citations


Cites background from "The potential adverse health effect..."

  • ...Dental amalgam as a potential source of mercury is a very controversial topic and views on Hg release from amalgam vary from the notion that there is no effect at all [Brownawell et al., 2005] to hypothesis that exposure to mercury from this source plays a role in the pathogenesis of theAlzheimer’s disease [Mutter et al....

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  • ...…potential source of mercury is a very controversial topic and views on Hg release from amalgam vary from the notion that there is no effect at all [Brownawell et al., 2005] to hypothesis that exposure to mercury from this source plays a role in the pathogenesis of theAlzheimer’s disease [Mutter…...

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Journal ArticleDOI
TL;DR: An overview of analytical methods, techniques and different approaches applied to the measurement of in vivo trace metals released into body fluids and tissues from patients carrying metal-on-metal prostheses and metal dental implants is given.

197 citations

References
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Journal ArticleDOI
Hill Ab1
TL;DR: The criteria outlined in "The Environment and Disease: Association or Causation?" help identify the causes of many diseases, including cancers of the reproductive system.
Abstract: In 1965, Austin Bradford Hill published the article "The Environment and Disease: Association or Causation?" in the Proceedings of the Royal Society of Medicine. In the article, Hill describes nine criteria to determine if an environmental factor, especially a condition or hazard in a work environment, causes an illness. The article arose from an inaugural presidential address Hill gave at the 1965 meeting of the Section of Occupational Medicine of the Royal Society of Medicine in London, England. The criteria he established in the article became known as the Bradford Hill criteria and the medical community refers to them when determining whether an environmental condition causes an illness. The criteria outlined in "The Environment and Disease: Association or Causation?" help identify the causes of many diseases, including cancers of the reproductive system.

6,992 citations

Journal Article
TL;DR: This paper contrasts Bradford Hill’s approach with a currently fashionable framework for reasoning about statistical associations – the Common Task Framework – and suggests why following Bradford Hill, 50+ years on, is still extraordinarily reasonable.
Abstract: In 1965, Sir Austin Bradford Hill offered his thoughts on: “What aspects of [an] association should we especially consider before deciding that the most likely interpretation of it is causation?” He proposed nine means for reasoning about the association, which he named as: strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment, and analogy. In this paper, we look at what motivated Bradford Hill to propose we focus on these nine features. We contrast Bradford Hill’s approach with a currently fashionable framework for reasoning about statistical associations – the Common Task Framework. And then suggest why following Bradford Hill, 50+ years on, is still extraordinarily reasonable.

5,542 citations


"The potential adverse health effect..." refers background in this paper

  • ...supported a causal relationship between dental amalgam exposure Case reports and studies of immune function consistently and adverse human health effects.[67] demonstrate that dental amalgam is capable of producing hyper-...

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27 Oct 1991
TL;DR: In this article, the effects of lead poisoning on the developing developing developing nervous system were investigated, including neurological, neurobehavioral, and developmental effects in children, and toxicity.
Abstract: Essentiality Toxicity Carcinogenicity Lead(Pb) Exposure Toxicokinetics Toxicity Neurologic, Neurobehavioral, and Developmental Effects in Children Mechanisms of Effects on the Developing Nervous System Peripheral Neuropathy Hematologic Effects Renal Toxicity Lead and Gout Effects on Cardiovascular System Immunotoxicity Bone Effects Reproductive Effects Birth Outcomes Carcinogenicity Other Effects Dose Response Treatment Organic Lead Compounds Mercury (Hg) Exposure Disposition and Toxicokinetics Metabolic Transformation Cellular Metabolism Toxicology Biological Indicators Treatment Nickel (Ni) Exposure Toxicokinetics Essentiality Toxicity Nickel Carbonyl Poisoning Dermatitis Indicators of Nickel Toxicity

1,727 citations

Journal ArticleDOI
TL;DR: The three modern "faces" of mercury are the authors' perceptions of risk from the exposure of billions of people to methyl mercury in fish, mercury vapor from amalgam tooth fillings, and ethyl mercury in the form of thimerosal added as an antiseptic to widely used vaccines.
Abstract: The three modern "faces" of mercury are our perceptions of risk from the exposure of billions of people to methyl mercury in fish, mercury vapor from amalgam tooth fillings, and ethyl mercury in the form of thimerosal added as an antiseptic to widely used vaccines. In this article I review human exposure to and the toxicology of each of these three species of mercury. Mechanisms of action are discussed where possible. Key gaps in our current knowledge are identified from the points of view both of risk assessment and of mechanisms of action.

975 citations


"The potential adverse health effect..." refers background in this paper

  • ...mercury represents only a small fraction (<10%) of total HgU, Methylmercury crosses the placenta and has neurological efmeasurements of HgU are less affected by dietary methylmercury fects on the developing foetus.[30] Significantly, maternal exposure exposure than are blood measurements....

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  • ...[18] brain[64-66] where it acts to alter the normal cellular processes of susceptible neuronal populations.[30] 5....

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  • ...Because of its lack of charge, gam restorations range from 3 to 17μg Hg/day and are based on unoxidised Hg0 is able to cross both the blood-brain and placental total Hg0 release that is dependent upon the total number and barriers.[30] It is estimated that 7% of an absorbed dose is deposited surface area of restorations, chewing and eating habits, and other in the brain following direct exposure to Hg0....

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  • ...[33] The where it diffuses across the alveolar membranes and enters the deposition of Hg2+ in the fetal brain is likely limited by the blood.[30] Approximately 7–14% of the absorbed dose is exhaled in oxidation of Hg0 in the fetal liver....

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Journal Article
TL;DR: This review provides an update on the current body of knowledge regarding the molecular interactions that occur between mercury and various thiol-containing molecules with respect to the mechanisms involved in the renal cellular uptake, accumulation, elimination, and toxicity of mercury.
Abstract: Mercury is unique among the heavy metals in that it can exist in several physical and chemical forms, including elemental mercury, which is a liquid at room temperature. All forms of mercury have toxic effects in a number of organs, especially in the kidneys. Within the kidney, the pars recta of the proximal tubule is the most vulnerable segment of the nephron to the toxic effects of mercury. The biological and toxicological activity of mercurous and mercuric ions in the kidney can be defined largely by the molecular interactions that occur at critical nucleophilic sites in and around target cells. Because of the high bonding affinity between mercury and sulfur, there is particular interest in the interactions that occur between mercuric ions and the thiol group(s) of proteins, peptides and amino acids. Molecular interactions with sulfhydryl groups in molecules of albumin, metallothionein, glutathione, and cysteine have been implicated in mechanisms involved in the proximal tubular uptake, accumulation, transport, and toxicity of mercuric ions. In addition, the susceptibility of target cells in the kidneys to the injurious effects of mercury is modified by a number of intracellular and extracellular factors relating to several thiol-containing molecules. These very factors are the theoretical basis for most of the currently employed therapeutic strategies. This review provides an update on the current body of knowledge regarding the molecular interactions that occur between mercury and various thiol-containing molecules with respect to the mechanisms involved in the renal cellular uptake, accumulation, elimination, and toxicity of mercury.

585 citations


"The potential adverse health effect..." refers background in this paper

  • ...A study of cells into bile and renal handling of Hg2+ likely also involves humans fed powdered dental amalgam demonstrated that approxiHg2+-glutathione complexes.[14] Because numerous sulfhydrylmately 0....

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  • ...It was argued that this step would reduce the occurrence events.[13,14] Such changes are often accompanied by increased of hypersensitivity reactions and localised side effects observed in urinary excretion of brush border enzymes, such as γ-glutamyl-...

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  • ...This results in an Hg2+ and prevent its interaction with sensitive proteins.[14] excretion rate of slightly more than 1% of the body burden per day....

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