THE EFFECT OF ULTRASONIC CONDENSATION ON DENTAL SILVER AMALGAM; A PRELIMINARY REPORT.
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Chemical Phenomena↗
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[Amalgam. VI. Allergy to mercury in dental materials; oral and systemic reactions].
Allergy for mercury in dental alloys can be responsible for the induction of allergic contact stomatitis. Evidence is also available for a role of mercury sensitization in the pathogenicity of oral lichen planus in particular. Aspects related to the development of allergic processes in the oral cavity are summarized. Allergy for mercury as the cause of oral mucosal reactions is rather rare in spite of the frequent use in dental amalgam, but probably underestimation of the incidence should be considered. Recent views with respect to the role of mercury as allergen in allergic contact stomatitis, oral lichen planus, the so-called Burning mouth syndrome and in systemic allergic reactions are summarized. Immunologic aspects in the pathogenesis are briefly discussed. Especially in cases in which the site or oral lesions is opposite to the dental alloy it is important to establish sensitization for mercury by use of epicutaneous path testing. When a positive test to mercury is obtained replacement of mercury containing alloys should be considered.
Dental Amalgam↗
Loading rate and temperature as variables in amalgam bending.
Three commercial dental amalgams of known dissimilar clinical properties were evaluated in pure blending at widely different loading rates and temperatures. Comparative data of fracture stress at 140 F rank these alloys according to their clinical fracture resistance; the phenomenon of creep may account for early marginal fracture prior to corrosion-induced fracture.
Dental Amalgam↗
Mercury in dental restoration: is there a risk of nephrotoxicity?
BACKGROUND: Concern has been voiced about exposure to mercury (Hg) from dental amalgam fillings, and there is a need to assess whether this leads to signs of nephrotoxicity. METHODS: A total of 101 healthy adults (80 males and 21 females) were included in this study. The population as grouped into those having amalgam fillings (39 males and 10 females) and those without (41 males and 11 females). Hg was determined in blood, urine, hair and nails to assess exposure. Urinary excretion of beta2-microglobulin (beta2M), N-acetyl-beta-D-glucosaminidase (NAG), gamma-glutamyltransferase (gammaGT) and alkaline phosphatase (ALP) were determined as markers of tubular damage. Albuminuria was assayed as an early indicator of glomerular dysfunction. Serum creatinine, beta2M and blood urea nitrogen (BUN) were determined to assess glomerular filtration. RESULTS: Hg levels in blood and urine were significantly higher in persons with dental amalgam than those without; in the dental amalgam group, blood and urine levels of Hg significantly correlated with the number of amalgams. Urinary excretion of NAG, gammaGT and albumin was significantly higher in persons with dental amalgam than those without. In the amalgam group, urinary excretion of NAG and albumin significantly correlated with the number of fillings. Albuminuria significantly correlated with blood and urine Hg. CONCLUSION: From the nephrotoxicity point of view, dental amalgam is an unsuitable filling material, as it may give rise to Hg toxicity. Hg levels in blood and urine are good markers of such toxicity. In these exposure conditions, renal damage is possible and may be assessed by urinary excretions of albumin, NAG, and gamma-GT.
Acetylglucosaminidase↗
Decrease of gamma 1 lattice constant with time in dental silver amalgam.
As a measure of the mercury content of the gamma 1 phase in dental silver amalgam, the lattice constant of this phase in different amalgams was determined at various times after trituration. The lattice constants of amalgams prepared from alloys with a high silver content have lower values and show a steeper decline with time than amalgams with a low Ag-content. Therefore, since a higher lattice constant presumably is associated with increased mercury vapor, the mercury vapor emission from amalgams with a low Ag-content probably is greater than from amalgams with a high Ag-content, especially during the first weeks after trituration.
Chemical Phenomena↗
Dentinal transport of mercury from dental silver amalgam restorations.
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Animals↗
Dutch dentists' conceptions of dental silver amalgam.
A sample of 468 dentists completed a questionnaire on their conceptions of amalgam. A minority (1-3%) reported that amalgam often causes toxic, galvanic and/or allergic side-effects. A considerably larger number (10-30%) stated that such side-effects 'sometimes' occur, while less respondents (6-11%) said they did not know. 60-80% said that such side-effects do not exist, or rarely. If a patient requested the removal of amalgam, one-third of dentists would do so often for cosmetic or toxic reasons, but only one-fifth in the case of a proven allergy. A very substantial percentage would not remove amalgam except for cosmetic reason. Substantial minorities thought that amalgam should not be used for pregnant women or children, or admitted that they did not know. The use of amalgam was rejected by 5%, while 9% could not decide whether they were for or against its use. Multivariate analysis reveals the existence of two dimensions in the data. The first dimension, referred to as "acceptance-of-amalgam", makes it possible to distinguish a subsample (about 9%) consisting of "rejectors-of-amalgam". On the second dimension, referred to as "conviction", a subsample (almost 20%) of "doubters" can be discerned, alongside "convinced adversaries" (about 4%) and "convinced advocates" (some 25%). The majority of the respondents are thought to be more or less in favour of the use of amalgam.
Attitude of Health Personnel↗
The Children's Amalgam Trial: design and methods.
The safety of silver amalgam as a dental restorative material has been controversial since its introduction 150 years ago, but until recently it has been assumed that the exposure to mercury from dental amalgam is limited to the acute placement phase. However, some recent studies have raised safety concerns by demonstrating chronic release of mercury vapor from amalgam fillings during chewing and brushing. The Children's Amalgam Trial is a two-arm randomized trial of safety, comparing amalgam with a mercury-free restorative material. A single masking procedure is used to ensure that all investigators and staff measuring outcomes are unaware of assigned trial arm. The study follows 534 New England children, aged 6-10 years at enrollment, for 5 years. The children were recruited from two northeastern U.S. communities, one in rural Maine and one in urban Massachusetts. No trial subjects received prior amalgam restorations, and all were in need of at least two posterior occlusal fillings. Participants were randomized to receive either amalgam or composite material for all posterior restorations at baseline and at subsequent visits. The primary endpoint will be 5-year change in IQ scores. Secondary endpoints will include measures of other neuropsychological assessments and renal functioning. This paper describes the design of the Children's Amalgam Trial and includes data on baseline characteristics of the subjects.
Child↗
Amalgam: dead or alive?
UNLABELLED: The use of dental amalgam is on the decline, yet its many advantages, including the contrast in colour with the tooth, increase the possibility that the patient's dentition will last a lifetime. CLINICAL RELEVANCE: Dental amalgam is still a viable restorative material. A recipe for the placing of better amalgam restorations along with clinical restorations of 30-year longevity using these techniques is presented.
Dental Amalgam↗
Effect of sodium hypochlorite and EDTA on mercury released from amalgam.
OBJECTIVES: The effect of sodium hypochlorite (NaOCl) and EDTA on mercury released from dental amalgam was assessed in vitro. STUDY DESIGN: Fifty-six samples of dental amalgam of similar size were prepared and exposed to a 10-mL solution of either 1% NaOCl, 3% NaOCl, 10% EDTA in 1% NaOCl, or 10% EDTA in 3% NaOCl for periods of 20, 40, and 60 minutes. Mercury concentrations in the solutions were measured by using a cold-vapor atomic absorption Mercury Analyzer System, and the differences between the groups were statistically analyzed. RESULTS: All amalgam samples exposed to 1% NaOCl and 3% NaOCl-either alone or in combination with EDTA-released mercury into the solutions. Mercury release was significantly higher in the test groups than in the EDTA, distilled water, or phosphate buffer controls (P <.001). Increase in the mean concentration levels of mercury in solution was time-dependent and directly related to NaOCl concentration. The addition of EDTA caused a reduction in mercury levels detected in solution, which was more significant in amalgam samples exposed to 1% NaOCl combined with EDTA (P <.001). CONCLUSIONS: NaOCl solutions commonly used for root canal cleaning and shaping cause mercury release from dental amalgam and may alter its chemo-physical properties as a sealant for root perforations.
Analysis of Variance↗
Copper-tin phases in dental silver amalgam alloy.
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Copper↗
[Bacterial colonization of dental materials: amalgam].
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Bacteria↗
Morphological findings and energy dispersive X-ray microanalysis of oral amalgam tattoos.
Oral amalgam tattoos (AT) are distinct pigmentations of the oral mucosa resulting from accidental incorporation of dental amalgam in the oral soft tissues. Dental amalgams and in particular mercury, one of the constituents of dental amalgams, have for long been considered toxic. Oral ATs are easily accessible to study soft tissue reaction to amalgam and its degradation products. In this study, 17 oral ATs were examined by transmission electron microscopy and energy dispersive X-ray microanalysis. Ultrastructurally, in the ATs, three kinds of electron-dense particles were observed. The largest particles ranged in size from 0.5 up to several 100 microm. Smaller electron-dense inclusions (0.5-0.1 microm) were seen extracellularly associated with meshworks of elastic fibers and collagen bundles. The third and smallest type of particles (5-30 nm in diameter) was found with basement membranes of small vessels and pericytes and particularly decorating collagen bundles. Element analysis regularly revealed the presence of silver, sulphur, copper and lead in the AT decay products. Mercury was found in only one instance. Tissue reactions due to ATs seem to be minimal. No acute inflammatory changes were seen. Larger inclusions occasionally were surrounded by macrophages and multinucleated cells. TEM and element analysis may in specific cases be helpful in the differential diagnosis of pigmented lesions of the oral mucosa.
Dental Amalgam↗
[Amalgam risk assessment with coverage of references up to 2005].
Amalgam, which has been in use in dentistry for 150 years, consists of 50 % elemental mercury and a mixture of silver, tin, copper and zinc. Minute amounts of mercury vapour are released continuously from amalgam. Amalgam contributes substantially to human mercury load. Mercury accumulates in some organs, particularly in the brain, where it can bind to protein more tightly than other heavy metals (e. g. lead, cadmium). Therefore, the elimination half time is assumed to be up to 1 - 18 years in the brain and bones. Mercury is assumed to be one of the most toxic non-radioactive elements. There are pointers to show that mercury vapour is more neurotoxic than methyl-mercury in fish. Review of recent literature suggests that mercury from dental amalgam may lead to nephrotoxicity, neurobehavioural changes, autoimmunity, oxidative stress, autism, skin and mucosa alterations or non-specific symptoms and complaints. The development of Alzheimer's disease or multiple sclerosis has also been linked to low-dose mercury exposure. There may be individual genetical or acquired susceptibilities for negative effects from dental amalgam. Mercury levels in the blood, urine or other biomarkers do not reflect the mercury load in critical organs. Some studies regarding dental amalgam reveal substantial methodical flaws. Removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials. Summing up, available data suggests that dental amalgam is an unsuitable material for medical, occupational and ecological reasons.
Adult↗
Mercury burden of human fetal and infant tissues.
UNLABELLED: The total mercury concentrations in the liver (Hg-L), the kidney cortex (Hg-K) and the cerebral cortex (Hg-C) of 108 children aged 1 day-5 years, and the Hg-K and Hg-L of 46 fetuses were determined. As far as possible, the mothers were interviewed and their dental status was recorded. The results were compared to mercury concentrations in the tissues of adults from the same geographical area. The Hg-K (n = 38) and Hg-L (n = 40) of fetuses and Hg-K (n = 35) and Hg-C (n = 35) of older infants (11-50 weeks of life) correlated significantly with the number of dental amalgam fillings of the mother. The toxicological relevance of the unexpected high Hg-K of older infants from mothers with higher numbers of dental amalgam fillings is discussed. CONCLUSION: Future discussion on the pros and cons of dental amalgam should not be limited to adults or children with their own amalgam fillings, but also include fetal exposure. The unrestricted application of amalgam for dental restorations in women before and during the child-bearing age should be reconsidered.
Adult↗
In vitro effects of mercuric chloride (HgCl2) on human mononuclear cells.
Due to the release of the toxic compounds of mercury from amalgam fillings, dental amalgam has been questioned as an adequate restoration material for tooth fillings. HgCl2 has been found to be mitogenic for human blood lymphocytes in vitro. However, activation required much higher concentrations than are ever found in vivo. This study has been initiated to evaluate further the influence of HgCl2 on human immunocompetent cells in vitro. It is found that HgCl2 in a narrow concentration range has the ability to preferentially stimulate the CD4+ T cell subset to blast transformation and DNA synthesis. The reaction, when monitored during days 2-6, is maximal at day 6, and most blasts express the IL-2 receptor (IL-2R), indicating in vitro activation. The CD8+ T cell subset is not affected to the same extent. In addition, HgCl2-induced lymphocyte reactivity is dependent on accessory cells, i.e. CD14+ cells.
Cells, Cultured↗
Isolation of silver- and antibiotic-resistant Enterobacter cloacae from teeth.
Antibiotic-resistant bacteria pose a serious threat to human health; hence the mechanisms that lead to their selection need to be investigated. One possible mechanism is that the silver and mercury in amalgam dental restorations may select for bacteria that contain heavy metal and antibiotic-resistance determinants, leading to the spread of these resistances, particularly if they are contained on the same mobile genetic element. The incidence of silver-resistant bacteria on teeth is investigated in this work. Two silver-resistant Enterobacter cloacae isolates were isolated from infected teeth containing dental restorations. Both isolates were also resistant to ampicillin, erythromycin, and clindamycin. The silE gene, which is encoded on the silver resistance operon, has been sequenced from both isolates. Results suggest that the silver resistance operon is encoded on plasmid DNA.
Dental Amalgam↗
Effects of hydrogen peroxide bleaching strip gels on dental restorative materials in vitro: surface microhardness and surface morphology.
OBJECTIVE: This study examined the effects of peroxide tooth bleaching, including Crest Whitestrips hydrogen peroxide gel treatments, on the surface hardness and morphology of common dental restorative treatments. METHODOLOGY: American Dental Association (ADA) recommended dental restorative materials, including amalgam, dental gold, porcelain, glass ionomer, and composites, were prepared according to manufacturers' instructions. A cycling treatment methodology was employed which alternated ex vivo human salivary exposures with bleaching treatments under conditions of controlled temperature and durations of treatment. Bleaching treatments included commercial Crest Whitestrips bleaching gels, which utilize hydrogen peroxide as the in situ bleaching source, and several commercial carbamide peroxide bleaching gels. Control treatments included placebo gels and an untreated group. Crest Whitestrips bleaching included treatment exposures simulating recommended clinical exposures (14 hours), along with excess bleaching simulating exposure to five times suggested Crest Whitestrips use. At the conclusion of treatments, surface microhardness measures and surface morphological assessments with standard and variable pressure (VP-) SEMs were conducted to assess the effects of bleaching exposure on the surface morphology and structural integrity of the restoratives. RESULTS: Surface microhardness and SEM measures revealed no significant deleterious effects on the restoration surfaces from Whitestrips gels. CONCLUSION: These results confirm that tooth bleaching from the selected commercial hydrogen peroxide or carbamide peroxide bleaching systems does not produce changes in surface morphology or microhardness of common dental restorative materials. These results support the clinical safety of the selected commercial bleaching systems to the oral environment, matching results obtained from long-term use of these ingredients applied in dental offices and available in commercial formulations.
Carbamide Peroxide↗