Mercury

“The issue of adverse health effects from dental amalgam and the concurrent low-dose exposure to inorganic mercury have been scrutinized by several Swedish expert groups during the past years. Only rarely have amalgam fillings in children been related to health effects. Experimental studies in genetically disposed animals have shown that low doses of inorganic mercury can induce autoimmune glomerulonephritis. The present case-control study included 31 children with acute glomerulonephritis and 33 with Henoch-Schönlein purpura retrieved from an in-patient register for the period 1973-1992 at the county hospital in Halmstad, Sweden. The median age was 10 and 9 years, respectively, for the two diagnostic groups. Dental clinics reported amalgam burden of the patients during the year before the date of diagnosis. Corresponding data were obtained for three randomly selected controls for each case, drawn from the case records of the same dental clinics, with matching for age and sex. Odds ratios (95% confidence interval) were 1.42 (0.49, 4.11) for Henoch-Schönlein purpura, 0.59 (0.25, 1.38) for acute glomerulonephritis and 0.84 (0.40, 1.75) for both diseases combined. The results of this study did not indicate increased disease risk in relation to amalgam burden.”

“The concentrations of mercury (Hg), cadmium (Cd) and lead (Pb) in brain (cerebrum) and kidney during fetal (second trimester terminations or abortions, n = 20) and postnatal (infants deceased before three months of age, n = 15) development have been studied. Information on possible sources of exposure was obtained from the mothers of the fetuses, but not from those of the infants. The median concentration of Hg in the brain was 4 micrograms/ kg wet weight in both fetuses and infants (total range < or = 2-23 micrograms/kg). The concentrations of Hg in the kidneys were significantly higher than in brain, median of Hg 6 micrograms/kg (range < or = 5-34 micrograms/kg) in fetuses and 10 micrograms/kg (< or = 7-37) in infants. There was a tendency of increasing concentration of Hg in the fetal kidney, but not in the brain, with increasing number of amalgam fillings in the mothers. The concentration of Cd in the brain was less than 1 microgram/kg in most cases, both in fetuses and infants. The concentration of Cd in the kidneys was significantly higher, with a median of about 2 micrograms/kg (1-8 micrograms/kg) in both groups. There was no detectable association between tissue Cd concentrations and the smoking habits of the mothers. The concentration of Pb in brain was below 10 micrograms/kg in most cases. In the kidneys, the concentrations of Pb were significantly higher, with a median of 12 micrograms/kg in the fetuses (range < or = 6-20 micrograms/kg) and 15 micrograms/kg (< or = 9-36 micrograms/kg) in the infants. In general, the concentrations of Cd and Pb were lower than in previously reported studies.”

“Pregnant rats were 1) administered methyl mercury (MeHg) by gavage, 2 mg/kg/day during days 6-9 of gestation, 2) exposed by inhalation to metallic mercury (Hg degrees) vapour (1.8 mg/m3 air for 1.5 h per day) during gestation days 14-19, 3) exposed to both MeHg by gavage and Hg degrees vapour by inhalation (MeHg + Hg degrees), or 4) were given combined vehicle administration for each of the two treatments (control). The inhalation regimen corresponded to an approximate dose of 0.1 mg Hg degrees/kg/day. Clinical observations and developmental markers up to weaning showed no differences between any of the groups. Testing of behavioural function was performed between 4 and 5 months of age and included spontaneous motor activity, spatial learning in a circular bath, and instrumental maze learning for food reward. Offspring of dams exposed to Hg degrees showed hyperactivity in the motor activity test chambers over all three parameters: locomotion, rearing and total activity; this effect was potentiated in the animals of the MeHg + Hg degrees group. In the swim maze test, the MeHg + Hg degrees and Hg degrees groups evidenced longer latencies to reach a submerged platform, which they had learned to mount the day before, compared to either the control or MeHg groups. In the modified, enclosed radial arm maze, both the MeHg + Hg degrees and Hg degrees groups showed more ambulations and rearings in the activity test prior to the learning test. During the learning trial, the same groups (i.e., MeHg + Hg degrees and Hg degrees) showed longer latencies and made more errors in acquiring all eight pellets. Generally, the results indicate that prenatal exposure to Hg degrees causes alterations to both spontaneous and learned behaviours, suggesting some deficit in adaptive functions. Coexposure to MeHg, which by itself did not alter these functions at the dose given in this study, served to significantly aggravate the changes.”

“The results of this study indicate that proper amalgam removal – and in some cases removal of all the other metals too – and replacement with biocompatible composites – can eliminate or reduce 80% of the classic symptoms of chronic mercury poisoning.

These results also show that the strength of an individual’s serum-globulin reactions, to many metals used in dentistry, especially the five metals present in amalgam, has important implications for recovery.”

“I. Background
1. Concerns over amalgam safety
Dental amalgam has been used in North America for more than 150 years, yet there have been recurrent concerns over its safety. In 1845, the American Society of Dental Surgeons adopted a resolution requiring its members not to use amalgam because mercury, the major component, was known to be extremely toxic. However, membership in the Society declined and it disappeared in 1856.”

“THE USE of mercury amalgams for dental fillings originated in France about 1826 (1) and shortly thereafter was introduced into the United States. Between 1835 and 1850 there raged what was known as the Amalgam War as a result of the proscription of mercury by the American Association of Dental Surgeons.”

“A survey was conducted on the possible factors influencing exposure to mercury vapour during the handling of amalgam and amalgam contaminated products at dental clinics in Norrbotten, the northern part of Sweden, as well as the current methods being used to minimise, if not prevent such exposures. Increased room temperature, a serious problem when working with amalgam, was the most common complaint from the dental personnel reflecting the observation that ventilation in most clinics was far from being satisfactory. However, methods of treating amalgam-contaminated waste products as well as the classification of products as high- or low-risk wastes also differed a lot. The results further showed that although majority of the dental personnel showed concern on the possible hazards of mercury vapour exposure and were interested in having the level of mercury vapour measured in their clinics, very few had access to any protective equipment against it. And among the few who had some forms of protective wear, most found the equipment disturbing and disruptive of work performance.”

“Dental amalgam releases small amounts of mercury, which is absorbed by the body. Available data are not sufficient to indicate whether this poses a health hazard to the general population. There is an urgent need for research into the potential health effects of mercury absorption from this source. However, considering the multiple benefits of dental amalgam, unless new scientific research dictates otherwise there is currently no justification for discontinuing the use of this material. Placing a priority on the preservation of healthy tooth structure through preventive strategies and the judicious use of all restorative materials could lessen current concerns over toxicity and unnecessary treatments.”

“OBJECTIVES:

To describe people with high mercury (Hg) uptake from their amalgam fillings, and to estimate the possible fraction of the occupationally unexposed Swedish population with high excretion of urinary Hg.

METHODS:

Three case reports are presented. The distribution of excretion of urinary Hg in the general population was examined in pooled data from several sources.

RESULTS:

The three cases excreted 23-60 micrograms of Hg/day (25-54 micrograms/g creatinine), indicating daily uptake of Hg as high as 100 micrograms. Blood Hg was 12-23 micrograms/l, which is five to 10 times the average in the general population. No other sources of exposure were found, and removal of the amalgam fillings resulted in normal Hg concentrations. Chewing gum and bruxism were the probable reasons for the increased Hg uptake. Extrapolations from data on urinary Hg in the general population indicate that the number of people with urinary excretion of > or = 50 micrograms/g creatinine could in fact be larger than the number of workers with equivalent exposure from occupational sources.

CONCLUSION:

Although the average daily Hg uptake from dental amalgam fillings is low, there is a considerable variation between people; certain people have a high mercury uptake from their amalgam fillings.”

“Although in use for more than 150 years, dental amalgam has been questioned more or less vigorously as a dental restoration material due to its alleged health hazard. Humans are exposed to mercury and the other main dental amalgam metals (Ag, Sn, Cu, Zn) via vapour, corrosion products in swallowed saliva, and direct absorption into the blood from the oral cavity. Dental amalgam fillings are the most important source of mercury exposure in the general population. Local, and in some instances, systemic hypersensitivity reactions to dental amalgam metals, especially mercury, occur at a low frequency among amalgam bearers. Experimental and clinical data strongly indicate that these and other subclinical systemic adverse immunological reactions to dental amalgam metals in humans will be linked to certain MHC genotypes, and affect only a small number of the exposed individuals. These individuals will be very difficult to detect in a mixed population of susceptible and resistant individuals, including persons with alleged symptoms due to dental amalgam fillings, where many of the individuals are likely to suffer from conditions with no proven immunological background such as multiple chemical sensitivity syndrome. Intensified studies should be performed to identify such susceptible MHC genotypes, taking advantage of the reported cases of more heavily metal-exposed humans with systemic autoimmune reactions. Further studies will also be needed to ascertain whether the combined exposure to the metals in dental amalgam may lower the threshold for adverse immunological reactions, since recent studies have shown that the metals in alloy, especially silver, may induce autoimmunity in genetically susceptible mice.”