Ex Vivo Mercury Release from Dental Amalgam after 7.0-T and 1.5-T MRI.

Purpose To evaluate ex vivo mercury release from dental amalgam after 7.0-T and 1.5-T MRI. Materials and Methods The authors evaluated 60 caries-free molar or premolar teeth that had been extracted for clinical indications. Two-sided cavities were opened in each tooth and amalgam fillings applied. After 9 days, two groups of 20 randomly selected teeth were placed in 20 mL of artificial saliva immediately followed by 20 minutes of MRI exposure at 1.5 or 7.0 T. A control group of teeth was placed in artificial saliva without undergoing MRI exposure. The teeth were removed from the artificial saliva 24 hours later, and the saliva was analyzed for mercury content by using inductively coupled plasma mass spectrometry. One-way analysis of variance was used to compare the mean mercury values among the three independent groups, and the Tukey test was used for multiple comparisons of the mean values. Results The mean mercury content of the artificial saliva was 673 µg/L ± 179 in the 7.0-T MRI group, 172 µg/L ± 60 in the 1.5-T MRI group, and 141 µg/L ± 152 in the control group. The mercury content in the 7.0-T group was greater than that in both the 1.5-T group (P < .001; 95% confidence interval: 368 µg/L, 633 µg/L) and the control group (P < .001; 95% confidence interval: 416 µg/L, 648 µg/L). There was no statistically significant difference in mercury content between the 1.5-T and control groups (P = .84; 95% confidence interval: -164 µg/L, 110 µg/L). Conclusion In an ex vivo setting, mercury was released from amalgam fillings after exposure to 7.0-T MRI but not 1.5-T MRI.

Characterisation of secondary metal-bearing phases in used dental amalgam and assessment of gastric solubility.

Detailed SEM/EDS investigation of used dental amalgams was carried out in order to characterise morphology and chemical composition of secondary metal-bearing phases resulting from long-term exposure of dental amalgam to oral environment, and assess their solubility in gastric environment. The investigation revealed numerous secondary phases, represented by compositionally and morphologically complex Hg-, Cu-, Sn-, Ag-, Zn-bearing sulphides and oxides/hydroxides, while sulphates and phosphates are scarce. Secondary metal-bearing phases mostly occur at the amalgam/tooth interface; however, some phases were found only on the occlusal surfaces of amalgam. Secondary phases mostly form porous aggregates of minute crystallites and micro- or nanocrystalline crusts. In oral environment, these phases are mostly stable and represent trapping media for dissolved potentially toxic metals released during amalgam corrosion. Simplified PHREEQC calculations of solubility of secondary metal-bearing phases in aqueous environment under conditions similar to those in gastric environment showed that secondary phases are more soluble in gastric environment than in oral solutions, which is mostly due to their forms of occurrence. Secondary phases in gastric environment thus act as secondary sources of potentially toxic metals, particularly Sn, Zn and also Cu, which are released both under reducing and oxidising conditions especially in acidic environment. Only very small amounts of Hg are potentially released and should not represent serious threat. Secondary phases that contribute the most to bioaccessibility of these metals are Sn hydroxychlorides, Sn oxides/hydroxides, Sn sulphates/hydroxysulphates, Sn oxides, Zn sulphides and Cu sulphides (Cu2S).

Correlation between long-term in vivo amalgam restorations and the presence of heavy elements in the dental pulp.

PROJECT: To measure the levels of heavy metals (Hg, Sn) in the dental pulp and blood samples of patients with long-term amalgam restorations. PROCEDURE: 12 amalgam restored and 12 non-restored, sound teeth were chosen and access cavity preparation to the pulp chamber was made. The contents were transferred and dissolved in 5mL of concentrated nitric acid followed by placement in an oven at 180°C for tissue digestion. After cooling the tubes each digested sample was transferred to an atomic absorption system to measure the levels of heavy metals. The blood samples of five patients in each group were randomly analyzed to determine the levels of these heavy metals in the blood and if there were a correlation between these levels in blood and pulp. Data were analyzed by t-test at a P<0.05 level of significance. RESULTS: No significant difference was seen between the levels of Hg and Sn in pulp tissues (P>0.05); however, the blood analysis showed higher level of Hg amalgam group (P=0.009). The analysis between the pulp and blood samples showed positive correlations for both Hg and Sn elements in dental pulp and the blood (P=1.000) (P=0.900). CONCLUSIONS: The long-term presence of dental amalgam (at least 5 years) did not result in any remarkable changes in the levels of mercury and tin in the pulp tissue; however, there were increases in the level of mercury in the blood circulation even five years following the placement of the restoration.

Human brain mercury levels related to exposure to amalgam fillings.

The safety of dental amalgam as the primary material in dental restoration treatments has been debated since its introduction. It is widely accepted that amalgam restorations continuously release elemental mercury (Hg) vapor, which is inhaled and absorbed by the body and distributed to tissues, including the brain. The aim of the present study was to investigate whether the presence of amalgam fillings is correlated with brain Hg level. The Hg levels in the parietal lobes of the brains of 32 cadavers were analyzed with an atomic absorption spectrometer with the mercury hydride system. A total of 32 brain samples were tested; of these, 10 were from cadavers with amalgam fillings, while 22 of them were amalgam free. Hg was detected in 60.0% (6 of 10) of the samples in the amalgam group and in 36.3% (8 of 22) in the amalgam-free group. The average Hg level of the amalgam group was 0.97 ± 0.83 µg/g (minimum: 0.3 µg/g and maximum: 2.34 µg/g), and in the amalgam-free group, it was 1.06 ± 0.57 µg/g (minimum: 0.17 µg/g and maximum: 1.76 µg/g). The results of the present study showed no correlation between the presence of amalgam fillings and brain Hg level.

Human exposure and health effects of inorganic and elemental mercury.

Mercury is a toxic and non-essential metal in the human body. Mercury is ubiquitously distributed in the environment, present in natural products, and exists extensively in items encountered in daily life. There are three forms of mercury, i.e., elemental (or metallic) mercury, inorganic mercury compounds, and organic mercury compounds. This review examines the toxicity of elemental mercury and inorganic mercury compounds. Inorganic mercury compounds are water soluble with a bioavailability of 7% to 15% after ingestion; they are also irritants and cause gastrointestinal symptoms. Upon entering the body, inorganic mercury compounds are accumulated mainly in the kidneys and produce kidney damage. In contrast, human exposure to elemental mercury is mainly by inhalation, followed by rapid absorption and distribution in all major organs. Elemental mercury from ingestion is poorly absorbed with a bioavailability of less than 0.01%. The primary target organs of elemental mercury are the brain and kidney. Elemental mercury is lipid soluble and can cross the blood-brain barrier, while inorganic mercury compounds are not lipid soluble, rendering them unable to cross the blood-brain barrier. Elemental mercury may also enter the brain from the nasal cavity through the olfactory pathway. The blood mercury is a useful biomarker after short-term and high-level exposure, whereas the urine mercury is the ideal biomarker for long-term exposure to both elemental and inorganic mercury, and also as a good indicator of body burden. This review discusses the common sources of mercury exposure, skin lightening products containing mercury and mercury release from dental amalgam filling, two issues that happen in daily life, bear significant public health importance, and yet undergo extensive debate on their safety.

Mercury (Hg) burden in children: the impact of dental amalgam.

The risks and benefits of using mercury (Hg) in dental amalgam have long been debated. This study was designed to estimate Hg body burden and its association with dental amalgam fillings in 182 children (ages: 5-15 years) living in Taif City. Hg was measured in urine (UHg), hair (HHg) and toenails (NHg) by the Atomic Absorption Spectrophotometer with Vapor Generator Accessory system. Urinary Hg levels were calculated as both micrograms per gram creatinine (µg/g creatinine) and micrograms per liter (µg/L). We found that children with amalgam fillings (N=106) had significantly higher UHg-C levels than children without (N=76), with means of 3.763 µg/g creatinine versus 3.457 µg/g creatinine, respectively (P=0.019). The results were similar for UHg (P=0.01). A similar pattern was also seen for HHg, with means of 0.614 µg/g (N=97) for children with amalgam versus 0.242 µg/g (N=74) for those without amalgam fillings (P=0). Although the mean NHg was higher in children without amalgam (0.222 µg/g, N=61) versus those with (0.163 µg/g, N=101), the relationship was not significant (P=0.069). After adjusting for many confounders, the multiple logistic regression model revealed that the levels of UHg-C and HHg were 2.047 and 5.396 times higher, respectively, in children with dental amalgam compared to those without (P<0.01). In contrast, a significant inverse relationship was seen between NHg levels and dental amalgam fillings (P=0.003). Despite the controversy surrounding the health impact of dental amalgam, this study showed some evidence that amalgam-associated Hg exposure might be related with symptoms of oral health, such as aphthous ulcer, white patches, and a burning-mouth sensation. Further studies are needed to reproduce these findings. The present study showed that significant numbers of children with or without amalgam had Hg levels exceeding the acceptable reference limits. The detrimental neurobehavioral and/or nephrotoxic effects of such an increased Hg on children should be a cause of concern, and further investigation is warranted. Our results are alarming and indicate an urgent need for biomonitoring and assessment of exposure. Changes in dental practices involving amalgam, especially for children, are highly recommended in order to avoid unnecessary exposure to Hg.

Immune function effects of dental amalgam in children: a randomized clinical trial.

BACKGROUND: Dental amalgam is a widely used restorative material containing 50 percent elemental mercury that emits mercury vapor. No randomized clinical trials have determined whether there are adverse immunological effects associated with this low-level mercury exposure in children. The objective of this study was to evaluate a subpopulation of the participants in the New England Children's Amalgam Trial for in vitro manifestations of immunotoxic effects of dental amalgam. METHODS: The authors conducted a randomized clinical trial in which children requiring dental restorative treatment were randomly assigned to receive either amalgam for posterior restorations or resin-based composite restorations. They assessed 66 children, aged 6 to 10 years, for total white blood cell counts, specific lymphocyte (T-cell and B-cell) counts and lymphocyte, neutrophil and monocyte responsiveness across a five-year period. Because of the small number of participants, the authors acknowledge that the study is exploratory in nature and has limited statistical power. RESULTS: The mean number of tooth surfaces restored during the five-year period was 7.8 for the amalgam group and 10.1 for the composite group. In the amalgam group, there was a slight, but not statistically significant, decline in responsiveness of T cells and monocytes at five to seven days after treatment; the authors consistently observed no differences at six, 12 or 60 months. CONCLUSIONS: The findings of this study confirm that treatment of children with amalgam restorations leads to increased, albeit low-level, exposure to mercury. In this exploratory analysis of immune function, amalgam exposure did not cause overt immune deficits, although small transient effects were observed five to seven days after restoration placement. CLINICAL IMPLICATIONS: These findings suggest that immunotoxic effects of amalgam restorations are minimal and transient in children and most likely do not need to be of concern to practitioners considering the use of this restorative dental material.

Dental amalgam and antibiotic- and/or mercury-resistant bacteria.

Mercury emitted from dental amalgam may select for increased numbers of antibiotic- or mercury-resistant commensal bacteria in patients and increase their risk for bacterial diseases that are resistant to common therapies. We hypothesized that the presence of dental amalgams would increase the level of mercury-, tetracycline-, ampicillin-, erythromycin-, or chloramphenicol-resistant oral and urinary bacteria as compared with levels in children receiving composite fillings. Samples were collected at baseline, 3-6 months after the initial dental treatment, and annually for 7 years of follow-up. There were no statistically significant differences between treatment groups in the numbers of bacteria growing on antibiotic- or mercury-supplemented plates. This study provided no evidence that amalgam fillings on posterior teeth influenced the level of antibiotic- or mercury-resistant oral or urinary bacteria as detected by culture.

Dental amalgam: few proven harmful effects but many ongoing concerns.

(1) Dental amalgam is one of the main sources of exposure to mercury in industrialised countries; (2) At high doses, mercury is both neurotoxic and nephrotoxic. A suspected link exists between chronic exposure to low doses of mercury derived from dental amalgam and renal, neurodegenerative or neurobehavioural disorders, but it has not been established; (3) Some individual cases are troubling, but epidemiological studies show no major effects in the general population. Various hypotheses have been proposed to explain why some people may be more sensitive than others to the effects of low-dose mercury; (4) More and more countries, especially Sweden, recommend that the use of amalgam should be restricted, particularly in pregnant women and children; (5) As part of a global strategy to eliminate mercury, the European Parliament has asked the Commission to draft legislation limiting the use of mercury in dental amalgam; (6) Evaluation of the risk-benefit balances of alternatives to dental amalgam does not provide sufficient data on which to base an informed choice between available options.

Blood and urine mercury levels in adult amalgam patients of a randomized controlled trial: interaction of Hg species in erythrocytes.

UNLABELLED: Parts of the population are permanently exposed to low levels of Hg degrees and Hg(II) from dental amalgam. It was the aim (1) to investigate the internal exposure to amalgam-related mercury from the kinetics of inorganic Hg in plasma and erythrocytes after amalgam removal, and (2) to estimate the amalgam-related absorbed dose. Dietary coexposure was monitored by determination of blood organic-Hg. Postremoval steady-state Hg concentrations were measured for 18 months. Eighty-two patients had been randomized into three groups: (A) removal of the fillings; (B) removal and non-specific detoxification, and (C) a health promotion program without removal. After amalgam removal, inorganic Hg dropped rapidly in plasma and red cells, stabilizing at 27% of preremoval levels after 60 days. Concentrations of organic Hg in plasma remained unchanged, indicating no change in dietary uptake of organic Hg. The concentration of organic Hg in red cells of group A was in the early postremoval phase lower and in the late postremoval phase higher than the preremoval control (p<0.01 for low-high difference). A protracted increase in organic Hg was also found in red cells of group B after 60 days. Thus, the effect of removal on organic Hg levels in the combined group A+B was compared with the values of group C in a linear mixed effects (LME) model which showed a significant increase with time in group A+B (p=0.028). In all groups, time profiles of urinary concentration and excretion of total-Hg were very similar to those of inorganic-Hg levels in plasma. From extrapolations of blood and urine data it was estimated that the amalgam-related inhalation and ingestion of Hg species were within the limits proposed by WHO, ATSDR and EPA. The integrated daily Hg dose absorbed from amalgam was estimated up to 3 microg for an average number of fillings and at 7.4 for a high amalgam load. CONCLUSIONS: This is the first study on adult amalgam patients which continuously monitored the postremoval decline of inorganic Hg and the coexposure from dietary organic Hg in a randomized-controlled-trial design. The integrated daily dose of 7.4 microg absorbed from a high amalgam load is well below the tolerable dose of 30 microg (WHO, 1990). The unexpected postremoval increase in erythrocyte organic Hg, which is associated with the depletion of cellular inorganic Hg, might result from binding of organic Hg to cellular sites previously occupied by inorganic Hg.

Scalp hair and urine mercury content of children in the Northeast United States: the New England Children's Amalgam Trial.

UNLABELLED: Children may be at particular risk from toxic effects of mercury (Hg). Previous studies of hair (organic) and urine (inorganic) Hg levels in US children were unable to assess Hg levels while accounting for exposure to amalgam dental restorations. This analysis describes, over a 5-year period, levels and correlates/predictors of scalp hair (H-Hg) and urinary (U-Hg) mercury in 534 New England Children's Amalgam Trial (NECAT) participants, aged 6-10 years and without exposure to dental amalgam at baseline. RESULTS: Mean H-Hg levels were between 0.3 and 0.4 microg/g over 5 years. 17-29% of children had H-Hg levels > or = 0.5 microg/g, and 5.0 to 8.5% of children had levels > or = 1 microg/g, in any given study year. In adjusted models, fish consumption frequency was the most robust predictor of high H-Hg. U-Hg mean levels were between 0.7 and 0.9 microg/g creatinine over two years. The percentage of those with U-Hg > or 2.3 microg/g creatinine ranged from 4% to 6%. Number of amalgam restorations had a significant dose-response relationship with U-Hg level. Daily gum chewing in the presence of amalgam was associated with high U-Hg.

Mechanisms of mercury disposition in the body.

Today the most widespread human exposures to mercury are to mercury vapor emitted from amalgam tooth fillings, to ethylmercury as a preservative in vaccines, and to methylmercury in edible tissues of fish. This review will focus on the mechanisms of transport of these three species of mercury. All three species are freely moveable throughout the body. Inhaled vapor in view of its physical properties as an uncharged atomic gas is believed to be transported by passive diffusion. Methylmercury and ethylmercury also move freely in the body. Methylmercury, and presumably its closely related chemical cousin ethylmercury, cross cell membranes as complexes with small molecular weight thiol compounds, entering the cell in part as a cysteine complex on the large neutral amino acid carriers and exiting the cell in part as a complex with reduced glutathione on endogenous carriers. The implications of these mechanisms with regard to biological monitoring are discussed.

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.

Copper, zinc, and selenium in human blood and urine after injection of sodium 2,3-dimercaptopropane-1-sulfonate: a study on subjects with dental amalgam.

This study investigated the effects of a single dose of intravenously administered sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) on the essential elements copper, zinc, and selenium in human blood and urine. The possible role of dental amalgam was also addressed. Eighty individuals, divided in four groups according to the presence or absence of dental amalgam fillings and symptoms self-related to such fillings, were given DMPS (2 mg/kg body wt) and 500 mL Ringer's acetate intravenously. Urine and blood were collected prior to the injection, and thereafter at intervals over a 24-h period. Cu, Zn, and Se concentrations were determined by atomic absorption spectrometry methods. A statistically significant increase in the concentrations of Cu and Zn in urine was observed 30 and 120 min after the DMPS injection compared to the preinjection concentrations. The concentrations of Se were not affected. The cumulated excretion over 24 h after DMPS injection constitutes only from 0.1% to 0.7% of the body content of these elements. There was no effect of different amalgam statuses on Cu and Zn excretion. We found a temporary decrease (4-7%) in the concentrations of Cu, Zn, and Se in blood 15 and 30 min after DMPS, but this seems to be the result of dilution factors. Administration of a single dose of DMPS does not affect the body stores of the essential elements Cu, Zn, and Se.

In vitro evaluation of the effect of freshly mixed amalgam and gallium-based alloy on the viability of primary periosteal and osteoblast cell cultures.

The effect of freshly mixed specimens of a gallium-based alloy Galloy and a high copper spherical amalgam Tytin on the viability of primary periosteal and osteoblast cells was investigated. The cells were grown from the parietal bones of 2-3 day old Albino Wistar rats and were seeded in multi-well plates and exposed to the test materials for 1 or 6 days. The number of viable cells in each test group was determined using the Trypan blue dye exclusion test and compared with the controls. The area of cell death around the test specimens was also measured. Statistical analysis (ANOVA, Tukey's pairwise comparisons) showed a significant effect of the test materials on cell viability (P < 0.01). The viability of cultures containing Tytin was significantly lower than cultures with Galloy and the controls (P < 0.05). The viability of cultures containing Galloy was significantly lower (P < 0.05) than controls except for periosteal cells after 1 day. The culture media was analysed using atomic absorption spectrophotometry (AAS) for metal ion content. The results suggested that mercury (Hg) was the main element released from the dental amalgam followed by copper (Cu) and silver (Ag) whilst gallium (Ga) was the main element released from the gallium-based alloy followed by indium (In), Ag and Cu.

[Dental amalgams and urine elimination of mercury in workers exposed to low concentrations of inorganic mercury]. / Amalgami dentari ed eliminazione urinaria di mercurio in lavoratori esposti a basse concentrazioni di mercurio inorganico.

The aim of the research was to assess the contribution of dental amalgams and other non-occupational factors of exposure to inorganic mercury (diet, etc.) to the quantity of mercury excreted with urine in workers exposed to low level concentrations of inorganic mercury. Two groups of workers (Groups I and II) were studied who were exposed to low and different environmental concentrations of inorganic mercury. These two groups were compared with a group of subjects not occupationally exposed to mercury in the same geographical area (Group III). All subjects were administered a questionnaire concerning personal data, lifestyle, recent removal and/or insertion of dental amalgam fillings, presence of nasal obstruction or bruxism and consumption of fish. The number of amalgam-filled teeth was established for each subject. Mean environmental exposure to inorganic mercury was 0.0087 mg/m3 for Group I and 0.0030 mg/m3 for Group II. Urinary excretion in the 3 groups was 4.2 +/- 2.8 micrograms/l for Group I, 3.0 +/- 2.1 micrograms/l for Group II and 1.6 +/- 1.2 micrograms/l for Group III. The results showed that of the factors of exposure to inorganic mercury, only occupational exposure (T = 9.18; p = 0.000) and the number of amalgam-filled teeth (T = 2.03; p = 0.043) were able to influence significantly urinary excretion of mercury; the sources of non-occupational exposure did not appear to play any role. The contribution of each amalgam filling to urinary mercury excretion was calculated to be 0.08 microgram/l. Occupational exposure therefore, even at low level doses, is still the main cause of urinary mercury excretion in workers exposed to inorganic mercury; of the non-occupational exposure factors, a significant role is played by amalgam dental fillings, whose contribution needs to be taken into consideration in order to make a correct interpretation of the results of biological monitoring of exposed workers.

[Mercury exposure from dental amalgam. Risk assessment and clinical evaluation]. / Kvikksølveksponering fra amalgam. Risikovurdering og medisinsk utredning.

Inorganic mercury is absorbed in small amounts from dental amalgam fillings. Exposure can be calculated by measuring the level of mercury in the blood or urine (u-Hg). The average u-Hg in Norwegians is approximately 2-3 micrograms/g creatinine (approximately 1-2 nmol/mmol creatinine). Classic signs of mercury poisoning occur in a fraction of long-term exposed subjects with u-Hg > 100 micrograms/g creatinine (56 nmol/mmol creatinine). Subtle effects (e.g. enzymuria, altered selenium metabolism, and changes in tremor spectra) have been reported in humans at average levels of 20-35 micrograms/g creatinine (approximately 11-20 nmol/mmol creatinine). There is widespread concern about possible adverse effects of mercury from amalgam fillings. Data on exposure-response relationships make it less likely that low-level mercury exposure from amalgam fillings should cause symptoms or physical signs. Studies of the association between symptoms and amalgam fillings have been negative. Patients with symptoms allegedly caused by mercury from amalgam should undergo thorough medical examination. Based on the patient's symptoms and physical signs adequate time should be allowed for careful recording of medical history, physical examination and relevant laboratory tests.