Whole-body imaging of the distribution of mercury released from dental fillings into monkey tissues

The fate of mercury (Hg) released from dental "silver" amalgam tooth fillings into human mouth air is uncertain. A previous report about sheep revealed uptake routes and distribution of amalgam Hg among body tissues. The present investigation demonstrates the bodily distribution of amalgam Hg in a monkey whose dentition, diet, feeding regimen, and chewing pattern closely resemble those of humans. When amalgam fillings, which normally contain 50% Hg, are made with a tracer of radioactive 203Hg and then placed into monkey teeth, the isotope appears in high concentration in various organs and tissues within 4 wk. Whole-body images of the monkey revealed that the highest levels of Hg were located in the kidney, gastrointestinal tract, and jaw. The dental profession's advocacy of silver amalgam as a stable tooth restorative material is not supported by these findings.     

Mercury from maternal “silver” tooth fillings in sheep and human breast milk

Neonatal uptake of mercury (Hg) from milk was examined in a pregnant sheep model, where radioactive mercury (Hg²⁰³)/silver tooth fillings (amalgam), were newly placed. A crossover experimental design was used in which lactating ewes nursed foster lambs. In a parallel study, the relationship between dental history and, breast milk concentration of Hg was also examined in 33 lactating women. Results from the animal studies showed that, during pregnancy, a primary fetal site of amalgam Hg concentration is the liver, and, after delivery, the neonatal lamb kidney receives additional amalgam Hg from mother's milk. In lactating women with aged, amalgam fillings, increased Hg excretion in breast milk and urine correlated with the number of fillings or Hg vapor concentration levels in mouth air. It was concluded that Hg originating from maternal amalgam tooth fillings transfers across the placenta to the fetus, across the mammary gland into milk ingested by the newborn, and ultimately into neonatal body tissues. Comparisons are made to the U.S. minimal risk level recently established for adult Hg exposure. These findings suggest, that placement and removal of “silver” tooth fillings in pregnant and lactating humans will subject the fetus and neonate to unnecessary risk of Hg exposure.     

Increased Zn/Glutathione Levels and Higher Superoxide Dismutase-1 Activity as Biomarkers of Oxidative Stress in Women with Long-Term Dental Amalgam Fillings: Correlation between Mercury/Aluminium Levels (in Hair) and Antioxidant Systems in Plasma

Background

The induction of oxidative stress by Hg can affect antioxidant enzymes. However, epidemiological studies have failed to establish clear association between dental fillings presence and health problems.

Objectives

To determine whether heavy metals (in hair), antioxidant enzymes (SOD-1) and glutathione levels could be affected by the chronic presence of heavy metals in women who had dental amalgam fillings.

Materials and Methods

55 hair samples (42 females with amalgam fillings and 13 female control subjects) were obtained. All subjects (mean age 44 years) who had dental amalgam filling for more than 10 years (average 15 years). Certain metals were quantified by ICP-MS (Mass Spectrophotometry) in hair (μg/g: Al, Hg, Ba, Ag, Sb, As, Be, Bi, Cd, Pb, Pt, Tl, Th, U, Ni, Sn, Ti) and SOD-1 and Glutathione (reduced form) levels in plasma. Data were compared with controls without amalgams, and analyzed to identify any significant relation between metals and the total number of amalgam fillings, comparing those with four or less (n = 27) with those with more than four (n = 15). As no significant differences were detected, the two groups were pooled (Amlgam; n = 42).

Findings

Hg, Ag, Al and Ba were higher in the amalgam group but without significant differences for most of the heavy metals analyzed. Increased SOD-1 activity and glutathione levels (reduced form) were observed in the amalgam group. Aluminum (Al) correlated with glutathione levels while Hg levels correlated with SOD-1. The observed Al/glutathione and Hg/SOD-1 correlation could be adaptive responses against the chronic presence of mercury.

Conclusions

Hg, Ag, Al and Ba levels increased in women who had dental amalgam fillings for long periods. Al correlated with glutathione, and Hg with SOD-1. SOD-1 may be a possible biomarker for assessing chronic Hg toxicity.     

A significant relationship between mercury exposure from dental amalgams and urinary porphyrins: a further assessment of the Casa Pia children’s dental amalgam trial

Previous studies noted specific changes in urinary porphyrin excretion patterns associated with exposure to mercury (Hg) in animals and humans. In our study, urinary porphyrin concentrations were examined in normal children 8–18 years-old from a reanalysis of data provided from a randomized, prospective clinical trial that was designed to evaluate the potential health consequences of prolonged exposure to Hg from dental amalgam fillings (the parent study). Our analysis examined dose-dependent correlations between increasing Hg exposure from dental amalgams and urinary porphyrins utilizing statistical models with adjustments for the baseline level (i.e. study year 1) of the following variables: urinary Hg, each urinary porphyrin measure, gender, race, and the level of lead (Pb) in each subject’s blood. Significant dose-dependent correlations between cumulative exposure to Hg from dental amalgams and urinary porphyrins associated with Hg body-burden (pentacarboxyporphyrin, precoproporphyrin, and coproporphyrin) were observed. Overall, 5–10% increases in Hg-associated porphyrins for subjects receiving an average number of dental amalgam fillings in comparison to subjects receiving only composite fillings were observed over the 8-year course of the study. In contrast, no significant correlations were observed between cumulative exposure to Hg from dental amalgams and urinary porphyrins not associated with Hg body-burden (uroporphyrin, heptacarboxyporphyrin, and hexacarboxyporphyrin). In conclusion, our study, in contrast to the no-effect results published from the parent study, further establishes the sensitivity and specificity of specific urinary porphyrins as a biomarker for low-level Hg body-burden, and also reveals that dental amalgams are a significant chronic contributor to Hg body-burden.     

Breast-milk mercury concentrations and amalgam surface in mothers from Brasília, Brazil

Human milk is the best source of nourishment for the newborn because of its incomparable balanced nutrition and psychological benefits to the infant's development. Dental fillings containing metallic Hg are the primary source of inorganic Hg contamination of humans. We studied Hg concentrations in the breast milk of mothers during the first month (7-30 d) postnatal in relation to the number of amalgam surfaces. The concentration of total Hg was determined in 23 samples of human milk collected from lactating mothers with a varied number of amalgam dental restorations. The average number of amalgam surfaces was 6.87 (5.81, SD) with a range of 0 to 20. The mean concentration of total Hg in breast milk was 5.73 ng/g (range: 0-23.07). The Pearson correlation coefficient was significant (r = 0.6087, p = 0.0057) between breast-milk Hg and number of amalgam surfaces. In 56.5% of low-fish-eating mothers, the amount of Hg likely to be ingested by breast-fed infants is above the World Health Organization reference.     

Assessment of some elements in human permanent healthy teeth,their dependence on number of metallic amalgam fillings,and interelements relationships

In this study, 60 human permanent healthy teeth (without filling) were collected postmortem and analyzed using flame atomic absorption spectrometry (FAAS), cold vapor atomic absorption spectrometry (CVAAS), hydride generation atomic absorption spectrometry (HGAAS), and electrothermal atomic absorption spectrometry (ETAAS) for the determination of Ca, Hg, Se, Cu, and Ag. The concentration of these elements was assessed in carious and noncarious teeth, different tooth groups, with age and with number of amalgam fillings. A negative correlation was found between Ca and the number of amalgam fillings, and significant negative correlations were found between Ca and three other metals (Hg, Ag, and Cu) that indicate the possibility of substitutions of Ca by three other metals. Significant positive correlations were found among the number of amalgam fillings and Hg, Ag, Cu and Se showed metal concentration in permanent healthy teeth were affected by the presence of the number of amalgam filling. In addition, significant positive correlations between Hg and Ag, Hg and Cu, and Ag and Cu proved the suspicion that the Hg content in permanent healthy teeth was mainly found because of the influence of amalgam filling, not from other sources. Moreover, the significant positive correlation between Hg−Se and Ag−Se showed the formation of mercuric selenide and silver selenide complexes as part of a natural mechanism of detoxification. Consequently, the permanent healthy teeth would be considered as a bioindicator for the accumulation of long-term exposure of Hg and Ag.     

Urinary mercury levels in females: Influence of skin-lightening creams and dental amalgam fillings

The influence of application of skin-lightening creams and dental amalgam fillings on the urinary mercury (Hg) level was evaluated in 225 females (ages 17 to 58 years) living in Riyadh, capital of Saudi Arabia. The arithmetic mean of the urinary Hg level was 6.96 ± 20.43 g l, in the range 0 to 204.8 g l. The mean urinary Hg level adjusted by creatinine (Cr) was 11.22 ± 37.23 g g Cr, in the range 0 to 459.37 g g. No significant difference in urinary Hg was noted between the females regarding the use of skin-lightening creams. On the other hand, results showed that urinary Hg concentration was influenced by the use and number of dental amalgam fillings. No women were identified with symptoms or signs that could be attributed to Hg intoxication. Urine analyses for creatinine, urea, uric acid, phosphorus, magnesium, glucose and calcium showed significant correlation with urinary Hg. This suggests that chronic exposure to Hg may be associated with a deterioration of renal function.     

Dental amalgam mercury exposure in rats

The aim of this study was to measure the distribution of mercury, in tissues of rats exposed to amalgam over a two months period. Possible interaction of mercury with copper and zinc in organs was also evaluated. Rats were either exposed to mercury from 4 dental amalgams, or fed the diet containing powdered amalgam during two months. Mercury was measured in the kidney, liver and brain, copper in kidney and brain and zinc in kidney. The results showed significantly higher concentrations of mercury in the kidneys and the brains of rats in both exposed groups compared to control. Even after two months of exposure to mercury brain mercury concentration in rats with amalgam fillings was 8 times higher than in the control and 2 times higher than in rats exposed to amalgam supplemented diet. The highest mercury concentration in the latter group was found in the kidneys and it was 5 times higher than in the control group. We found no significant differences between mercury levels in exposed and control rat's liver. Exposure to mercury from dental amalgams did not alter the concentrations of copper and zinc in the tissues. Histopathological analyses of rats tissues did not show any pathological changes. These results support previously proposed nose-brain transport of mercury released from dental amalgam fillings.     

Concentrations of major elements and mercury in unstimulated human saliva

The aim of this study was a preliminary assessment of a possible role of human saliva in the diagnosis of some physiological and pathological changes in oral and body functions. Reliable procedures for collection and analysis of samples were established in order to assess total concentrations of Ca, K, Mg, Na, P, and Hg in whole unstimulated saliva. Possible relationships between element concentrations and sex, age, smoking, illness conditions, or side effects resulting from the use of drugs were investigated. The effects of stimulated or unstimulated collection procedures, dental prosthesis, and amalgam fillings were also evaluated. Total concentrations of major cations and Hg in whole saliva from 33 healthy adults living in the Siena district showed a coefficient of variation ranging from 11% (P) to 53% (Na) and average values were in the same range of those previously reported for unstimulated saliva. Healthy males had significantly higher concentrations of K, Na, P, and Na/K, Na/Ca, Na/Mg, and Na/P values than females. Age, smoking, dental prosthesis, and amalgam fillings had no significant effects on the concentrations of major elements. On the contrary, concentrations of Hg were positively correlated to the number of amalgam fillings and increased at a rate of about 1.9 μg/L for each filling. No correlations were found between Hg concentrations and those of major elements. Comparisons with literature data showed a different composition (particularly for Na and Hg concentrations) between unstimulated and stimulated saliva. Samples from patients affected by idiopathic pulmonary fibrosis had significantly higher concentrations of K and the maximum value was measured in a patient affected by acute pulmonary edema. This increase was likely the result of pharmacological treatments with tricyclic antidepressants and/or saline solutions. Data reported in this study, although preliminary, contribute to the assessment of levels of major cations (some of them very little investigated) and Hg in whole unstimulated human saliva and provides consistent support for further research on the possible use of this easy accessible matrix as a diagnostic tool of body function changes.     

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 μg, median value) over 24 hours than those without amalgam (47.5 μg) (p=0.016). There was no difference in selenium excretion between groups with (42.4 μg) and without (39.4 μg) 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.     

Elimination of mercury from amalgam in rats.

The aim of this study was to measure the urinary mercury excretion in rats exposed to amalgam over a two months period. Animals were either exposed to mercury from 4 dental amalgams or fed the diet containing powdered amalgams. The results showed significantly higher mercury amount in urine of both exposed groups than in control. Even two months after the amalgam had been placed in rats teeth, the amount of mercury in the urine remained 4-5 times higher than in control, and 4 times higher than in rats exposed to diet containing powdered amalgam. The elevated urinary Hg amount was accompanied by an increased level of total protein in urine. In the same exposure period the excretion of total protein in urine of rats with amalgam fillings was 2 times higher than in control and 1.5 times higher than in rats exposed to amalgam through diet. Concentrations of mercury in the sera of all groups were below the detection limit of the method. The results show that amount of mercury and protein in the urine of rats were related to the mercury release from dental malgam.     

Mercury Exposure and Risks from Dental Amalgam in Canada: The Canadian Health Measures Survey 2007–2009

Dental amalgam is 50% metallic mercury (Hg⁰) by weight and causes Hg exposure. The first assessment of Hg exposure and risk from dental amalgam in Canada was published in 1996. Recent data provided the opportunity to update that assessment. During the Canadian Health Measures Survey (CHMS; 2007 to 2009) the number of tooth surfaces specifically restored with dental amalgam was recorded. Data were also collected on the concentration of Hg in urine of survey participants. These data were employed to determine Hg exposures in the Canadian population. Also determined was the number of amalgam-restored tooth surfaces that would not result in exposure exceeding the dose associated with Canada's reference exposure level (REL) for Hg⁰. Based on the CHMS data, 17.7 million Canadians aged ≥6 years collectively carry 191.1 million amalgam surfaces, representing 76.4 million amalgam-restored teeth. Average Hg exposures were: Children—0.065 μg Hg/kg-day; Teens—0.032 μg/kg-day; Adults—0.033 μg/kg-day; and Seniors—0.041 μg/kg-day. Of Canadians with dental amalgam restorations, 80.4% experience a daily dose of Hg that exceeds the Canadian REL-associated dose. The number of amalgam surfaces that will not result in exceeding the REL-associated dose varied from two amalgam surfaces (children, both sexes) to seven surfaces (adult males).     

The Relation Between Human Exposure to Mercury and Thyroid Hormone Status

The aim of this study was to investigate total mercury (THg) and methylmercury (MeHg) exposure of 75 mother-child pairs in relation to their thyroid hormone status (thyroid-stimulating hormone (TSH), triiodothyronine (T3), free triiodothyronine (fT3), thyroxine (T4), and free thyroxine (fT4)). THg and MeHg in blood samples were measured by atomic absorption spectrometry and gas chromatography-inductively coupled plasma-mass spectrometry, respectively. The median THg and MeHg levels in maternal blood, cord blood, and blood of 6-month-old children were 0.50, 0.53, and 0.32 and 0.22, 0.32, and 0.08 μg/L, respectively. There were significant correlations between paired maternal-cord blood levels for THg and MeHg, with a greater transplacental transport of MeHg compared with THg (mean cord/maternal blood ratio, 1.80 vs. 1.24). The maternal blood THg was found to be a better predictor of TSH levels in children than their current THg exposure. There was a positive correlation between maternal THg and children's TSH. T3 and fT3 levels in children were negatively related to cord blood THg in the majority (Caucasian) subgroup, whereas these associations were positive in the Roma subgroup. Mothers with dental amalgam fillings had significantly lower T4 and fT4 levels. Moreover, fT4 in the mothers of boys negatively correlated with maternal THg levels. MeHg exposure lowered T3 levels in the mothers of girls. Our results suggest that low-level exposure to Hg can affect thyroid hormone status during prenatal and early postnatal exposure depending on the form of Hg, gender, ethnicity, lifestyle, or socioeconomic status (dental amalgam fillings).     

Aggravated neuromuscular symptoms of mercury exposure from dental amalgam fillings

Dental amalgam fillings are widely used all over the world. However, their mercury content can lead to various side effects and clinical problems. Acute or chronic mercury exposure can cause several side effects on the central nerve system, renal and hepatic functions, immune system, fetal development and it can play a role on exacerbation of neuromuscular diseases. In this case, we will present a patient with vacuolar myopathy whose symptoms were started and aggravated with her dental amalgam fillings.     

Amalgam fillings and cognitive abilities in a representative sample of the elderly population

Objectives: The ongoing controversial discussion about a possible negative effect of amalgam fillings on the cognitive abilities and the pathogenesis dementia was the objective of the present study. Sample: A total of 300 patients aged from 70 to 103 years were selected from the multidisciplinary ‘Berlin Aging Study’ (Base). The sample was heterogeneous concerning lifestyle, education and social prestige. According to their dental state subjects were allocated into three groups: edentate ≥20 years (I) and residual teeth without (II) or with (III) amalgam restorations. All groups were matched for age and gender. Design: Dental examinations and various psychiatric as well as psychological assessments were carried out by professionals within the protocol of the BASE. Tests were chosen to reveal the presence and degree of dementia and assess cognitive abilities such as ‘perceptual speed’, ‘reasoning’, ‘memory’, ‘fluency’ and ‘knowledge’. Results: The present findings negate a correlation between the dental state and the pathogenesis of dementia and the physiological age‐related decline in cognitive abilities. Thus the presence of amalgam fillings did neither correlate to a demented mental condition nor an impaired cognitive performance.     

Dental amalgam and mercury

Summary Mercury concentration in intraoral air and urine of seven females with dental amalgam was measured before and after intake of one hard-boiled egg. A considerable decrease in mercury concentration in intraoral air was found. Twenty women with about equal dental amalgam status, with or without subjective symptoms related to dental amalgam, were also studied. Mercury concentrations in intraoral air and urine were measured. For all the 27 women the basal intraoral air concentration of mercury ranged over 0.6–10.4 g/m³ (median value 4.3 g/m³). This corresponds to a release of 0.02–0.38 ng/s (median value 0.16 ng/s). In urine, the mercury concentration varied from < 0.8–6.9 g/g creatinine (median value 1.9 g/g creatinine). Data from both parameters were significantly correlated to the total number of teeth areas with dental amalgam. Protein values in urine indicated no renal damage. Maximum concentrations of mercury vapour in intraoral air for the 27 women who had chewed chewing gum for 5 min varied between 2–60 g Hg/m³ (median value 19 g Hg/m³). This corresponds to 0.07–2.20 ng Hg/s and a median value of 0.70 ng Hg/s.     

Mercury and selenium in whole blood and serum in relation to fish consumption and amalgam fillings in adolescents

Mercury and selenium in whole blood and serum of 245 17-year old Swedish adolescents were analysed. The relationships between these elements' concentrations and the consumption of fish as well as the number of dental amalgam fillings were studied. The geometric means (GM) of the mercury concentrations were 1.1 microg/L in blood and 0.43 microg/L in serum. The mean selenium concentration in blood was 110 microg/L and the GM of the serum selenium concentration 110 microg/L. Fish species with dietary restrictions due to elevated mercury Levels (i.e. pike, perch, pikeperch, burbot, eel and halibut) were consumed on average 0.7 times/month and fish species without such restrictions 4.1 times/month. Despite this comparatively low fish consumption, the adolescents' blood mercury concentrations were positively correlated with fish consumption. Of the adolescents, 39% had amalgam fillings (mean 2 +/- 1.5). Serum mercury was influenced by the number of amalgam fillings, by fish consumption, blood and serum levels of selenium and the residential area. Blood and serum selenium concentrations were not influenced by fish consumption, but were positively associated with the serum mercury concentration.     

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.     

Mercury Exposure Assessment in Iranian Pregnant Women’s Hair with Respect to Diet, Amalgam Filling, and Lactation

Our aim for carrying out this study was to estimate the levels of mercury in the hair of pregnant women and its association with fish consumption and amalgam fillings. From November 2007 to January 2008, 100 hair samples were collected randomly from three groups of pregnant women: Ahvaz in the south of Iran, Noushahr in the north, and the countryside of Noushahr. Significant differences were found in these three groups of pregnant women's samples (p>0.05). The mean mercury level in women's hair was found to be 0.37 μg/g (range, 0.11-3.57 μg/g). Only in 2 % of collected hair samples did the total mercury (THg) level exceed the United States Environmental Protection Agency-recommended 1.0 μg/g. In addition, there was a positive correlation of THg content in Ahvaz group's samples with respect to fish consumption (r=0.41, p=0.02) and a negative correlation of THg content in those who consumed vegetables and fruit. The level of education also played an indicating factor in this group. Moreover, significant association was found between the residence time and Hg concentration of women's hair samples collected from Noushahr (p>0.05). Similarly, the same correlations were found between hair mercury levels and the time since the first filling, number of dental fillings, pregnancy interval, and lactating period.     

Linkage of a novel mercury resistance operon with streptomycin resistance on a conjugative plasmid in Enterococcus faecium

It has been shown that the mercury in dental amalgam and other environmental sources can select for mercury resistant bacteria and that this can lead to an increase in resistance to antibiotics. To understand more about this linkage we have investigated the genetic basis for mercury and antibiotic resistance in a variety of oral bacteria. In this study we have cloned and sequenced the mer operon from an Enterococcus faecium strain which was resistant to mercury, tetracycline, and streptomycin. This strain was isolated, in a previous investigation, from a cynomolgus monkey post-installation of amalgam fillings. The mer operon was contained within a putative transposon (Tnmer1) of the ISL3 family. This element was located on a streptomycin resistant plasmid, pPPM1000, which shares homology with pRE25.