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“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.”

“The sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (DMPS) challenge test (300 mg p.o. after an 11-hr fast) was given in Monterrey, Mexico to dental and nondental personnel. Urine samples were collected and analyzed for total mercury. The mean mercury urinary excretion (+/- S.E.) for 6 hr before and 6 hr after DMPS administration for 10 dental technicians, who formulate amalgam, was 4.84 micrograms +/- 0.742 and 424.0 micrograms +/- 84.9; for 5 dentists, who use amalgam in their practice, 3.28 micrograms +/- 1.11 and 162.0 micrograms +/- 51.2; and for 13 nondental personnel, 0.783 microgram +/- 0.189 and 27.3 micrograms +/- 3.19. The urinary coproporphyrin levels before DMPS administration, which are indicative of renal mercury content, were quantitatively associated with the urinary mercury levels among the three study groups after DMPS administration. This was not so if the urinary mercury level before DMPS administration was compared with the urinary coproporphyrin concentration. The urinary mercury level after DMPS administration is a better indicator of exposure and renal mercury burden than is the mercury level measured in the urine before DMPS is given. Regression analysis showed that the coefficient of urinary mercury was statistically and adversely associated with complex attention (switching task), the perceptual motor task (symbol-digit substitution), symptoms and mood. The easily performed DMPS-mercury challenge test is useful for monitoring dental personnel for mercury vapor exposure.”

“OBJECTIVES:

This project was conducted to examine whether the computerised analysis of psychomotor responses available from Cognitive Drug Research is appropriate for measuring an effect of low level exposure to mercury in dentists.

METHODS:

A computerised battery of psychomotor tests was given to two groups of dentists (older dentists and trainees) and to two age matched control groups. As well as the psychomotor tests, volunteers were required to complete a questionnaire to identify potential influences on psychomotor performance and to provide a sample for analysis of urinary mercury.

RESULTS:

Statistical analysis of the results showed that the older dentists had slightly higher concentrations of urinary mercury although most were around background levels and they were all within occupational limits. Five of the psychomotor tests showed no differences between the performance of the four groups. The older dentists showed significantly better performance on the simple reaction time test and significantly poorer performance in the immediate word recall and delayed word recall tests.

CONCLUSIONS:

Poorer performance in memory recall tests confirms previously reported studies. This together with the confirmation that this test system is a practical tool in the occupational setting suggests that a larger study of the effects of mercury exposure on dentists would be appropriate.”