Mercury

“Health Canada recently lowered the recommended maximum daily exposure of mercury from all sources for women of child-bearing age and for children less than 10 years. This new exposure guideline does not seem to be based on any new scientific finding of human toxicity. The average daily intake of methylmercury (mainly from fish) that may cause demonstrable health effects in the most sensitive individual is 300 micrograms/day, or 4.3 micrograms Hg/day/kg body weight. The new, lower Health Canada limit is 95% below the level that may cause health effects. A number of studies have looked at methylmercury in human breast milk (where maternal consumption of fish is high), but no strong evidence of toxicity has been reported. The amount of mercury released from dental amalgam is minimal; a person would have to have 490 amalgam surfaces for there to be enough mercury vapour and ionic mercury given off from amalgam fillings to meet the maximum exposure guidelines. The uptake of food-related organic mercury is six times higher than the uptake of mercury from amalgam; moreover, food-related mercury is significantly more toxic. Many studies of amalgam-related mercury are flawed by confusion between exposure and absorption for the various forms of mercury, a limited selection of data, the ignoring of confounding variables or the misclassification of data.”

The findings presented here suggest that mercury poisoning from dental amalgams may play a role in the etiology of oral health disorders in multiple sclerosis (MS) patients. Comparsions between MS subjects with dental amalgams and a control group of MS subjects without amalgams found significantly fewer oral cavity symptoms per subject in the amalgam-removal group during twelve months. They had fewer symptoms of metallic taste, foul breath, grinding teeth, and loss of taste. MS subjects with amalgam removal had significantly higher counts of total T-lymphocytes, T-8 suppressor cells, and a lower T-4 helper to T-8 suppressor ratio. The MS amalgam group had significantly lower levels of IgG, and the female MS amalgam subjects had significantly lower levels of IgM. The hair mercury levels of MS patients were significantly higher when compared to a control group of non-MS subjects.

RESULTS:
Of 19 patients with OLL adjacent to amalgam fillings, 15 (78.9%) were sensitized to inorganic mercury (INM), significantly more than those with OLL not adjacent to amalgam, other oral diseases or complaints, and the control group. In 5 of 15 (33.3%) of the patients with OLL, a positive patch test to INM was observed only at D10 or D17. Amalgam was removed in 18 patients with OLL (sensitization to INM: 15), and in 11 patients with OLP (sensitization to INM: 2). After removal, the lesions of 13 of 15 of the INM-sensitized patients with OLL (86. 7%) and 2 with OLP healed or improved significantly, but this was not observed with the INM negative patients. Frequency of sensitization to gold sodium thiosulfate (GST) and palladium chloride 1% pet (PDC) was high in all groups. This was partly because readings were performed late. Lesions of 2 patients with allergic contact stomatitis caused by gold and 1 caused by palladium healed completely after removal of these restorations. Histologically, lichenoid changes were observed in 14 of 36 biopsy specimens of positive patch tests from INM (9/21), GST (2/10), and PDC (3/5) in all patient groups, mainly in persistent patch tests at D10 or D17. This was not observed in 12 biopsy specimens taken from persistent patch tests from other substances, including nickel sulfate.

CONCLUSION:
Our results suggest that sensitization to mercury is an important cause of OLL, whether all lesions or only a part of them are adjacent to amalgam fillings. Sensitization to GST may reflect true gold allergy and should be considered as a cause of oral diseases in some patients. Sensitization to PDC is frequent but has yet only little clinical relevance. Patch tests may be positive only at D10 or D17. This suggests the importance of additional readings of GST, PDC, and mercury salts at this time.

BACKGROUND:
Mercury, or Hg, is a neurotoxin that has been speculated to play a role in the pathogenesis of Alzheimer’s disease, or AD. Dental amalgam releases low levels of Hg vapor and is a potential source of Hg for a large segment of the adult population.

METHODS:
The authors studied 68 subjects with AD and 33 control subjects without AD to determine Hg levels in multiple brain regions at autopsy and to ascertain the subjects’ dental amalgam status and history. The subjects were from central Kentucky and Elm Grove, Wis. The authors conducted dental amalgam assessments during the lives of the majority of subjects and in some subjects at the time of autopsy only. The authors also determined three dental amalgam index scores–Event (placement, repair or removal of amalgam), Location and Time In Mouth–in addition to the numbers of and surface area of occlusal amalgam restorations. The authors determined Hg levels in multiple brain regions and performed full neuropathologic evaluations to confirm the normal status of the brain or the presence of AD.

RESULTS:
The authors found no significant association of AD with the number, surface area or history of having dental amalgam restorations. They also found no statistically significant differences in brain Hg level between subjects with AD and control subjects.

CONCLUSIONS:
Hg in dental amalgam restorations does not appear to be a neurotoxic factor in the pathogenesis of AD. The authors found that brain Hg levels are not associated with dental amalgam, either from existing amalgam restorations or according to subjects’ dental amalgam restoration history.

“Thimerosal is an organic mercurial compound widely used as a preservative in vaccines, eyedrops, and contact lens cleaning and storage solutions. 5 infants, 2 female and 3 male, ranging in age from 7 to 28 months and affected by atopic dermatitis (AD) diagnosed according to the Hanifin and Rajka criteria, experienced an exacerbation of their clinical condition 2-10 days after mandatory vaccinations with vaccines containing thimerosal. Cutaneous lesions of nummular eczema appeared on the trunk, limbs and face. All patients were patch tested with serial dilutions of thimerosal in petrolatum. A positive patch test reaction to thimerosal 0.1% pet. was observed in all 5 children. 3 of them also showed a positive reaction at 0.01% and 0.05% pet. Despite their thimerosal-hypersensitivity, all children completed the entire series of mandatory vaccinations, care being taken to use different needles for injection and aspiration of the vaccine. The 2-year follow-up did not reveal other episodes of exacerbation of the AD after vaccination. The present study confirms the high frequency of sensitization to thimerosal in atopic children and suggests that vaccination can cause clinical symptoms in sensitized children. Nevertheless, sensitization to thimerosal does not prevent children from continuing with mandatory vaccinations.”

Recent studies have investigated a mercury-free silver alternative to amalgam, but the silver powders required a relatively high compaction pressure to consolidate. The aim of the present study was to consolidate a precipitated silver powder into a cohesive solid using an air-driven pneumatic condenser fitted with an amalgam plugger at a clinically realistic load, and to study the mechanisms and rates of three-body wear of the consolidated silver in comparison with that of an amalgam. The silver powder was annealed, rinsed with a dilute acid, and consolidated either in a prepared tooth cavity or in a specimen mold at a load of 15 N. A four-station wear machine was used where each specimen was immersed in a slurry containing polymethyl methacrylate beads, then a steel pin was loaded and rotated against the specimen at a maximum load of 76 N. The flexural strength in MPa (mean +/- SD; n = 10) was 86 +/- 20 for amalgam, 181 +/- 45 for silver with a polished surface, and 202 +/- 21 for silver with a burnished surface. After 4 x 10(5) wear cycles, the wear scar depth in microm was 134 +/- 54 for amalgam, 143 +/- 8 for polished silver, and 131 +/- 9 for burnished silver, which were not significantly different (Tukey’s multiple comparison test; family confidence coefficient = 0.95). SEM examination revealed cracks and fracture pits in the worn surface of amalgam, in contrast to a smooth surface in silver. Wear and material removal in amalgam occurred by microfracture and dislodgement of cracked segments, while wear in the silver occurred by ductile deformation and flow of materials. To conclude, the consolidated silver possesses a three-body wear resistance similar to that of amalgam, and a higher resistance to wear-induced damage and cracking than amalgam. The mechanism of wear in amalgam is microfracture and material dislodgement, while that in consolidated silver is ductile deformation and flow of material.

“Parathyroid cells express a plasma membrane calcium receptor (CaR), which is stimulated by a rise in extracellular calcium concentration ([Ca2+]ext). A decreased sensitivity to [Ca2+]ext occurs in adenomatous parathyroid cells in patients with primary hyperparathyroidism, but the underlying functional mechanism is not yet fully understood. This study explored whether CaR responsiveness is influenced by increasing the affinity of IP3 receptors–a major signalling component of other G-protein-coupled receptors. The sulphydryl reagent thimerosal was used to increase the responsiveness of IP3-receptors. Quantitative fluorescence microscopy in Fura-2-loaded cells was used to investigate the effects of thimerosal on the cytoplasmic calcium concentrations ([Ca2+]i) in human parathyroid cells and to compare its effects in a rat medullary thyroid carcinoma cell line (rMTC6-23) also expressing CaR. During incubation in Ca(2+)-free medium, thimerosal 5 microM induced a rapid sustained rise in [Ca2+]i in human parathyroid cells and no further [Ca2+]i increase appeared in response to the CaR agonist Gd3+ (100 microM). Thimerosal 1 microM induced only slow and minimal changes of basal [Ca2+]i and allowed a rapid response to Gd3+ 20 nM (a concentration without effect in control cells). The slope of the thimerosal-induced [Ca2+]i responses was steeper following exposure to CaR agonists. In the presence of 1 mM [Ca2+]ext, thimerosal (0.5 microM) induced a sharp increase in [Ca2+]i to a peak (within 60 s), followed either by return to basal [Ca2+]i or by a plateau of slightly higher amplitude. Similar results were obtained using rMTC6-23 cells. Thimerosal increases the responsiveness to CaR agonists through modulation of the sensitivity of the IP3 receptor in both parathyroid and rMTC6-23 cells.”

The goal of this study was to investigate the effectiveness of stand-alone modular air purification sys-tems in improving air quality in dental practices, hospital and laboratory environments. As air pollu-tant make-up and concentration may vary significantly in different indoor environments, the air clean-ing technologies utilised should be optimised for the pollutants targeted in a particular environment. Reduction of mercury vapours and formaldehyde were examined because of their importance for indoor air quality in dental practices. In addition, the reduction of particles and microorganisms was investigated as well as the removal of substances which are noticeable due to their strong odours. The air purifiers used in the study were configured to contain the most suitable air cleaning technology for each of the indoor environments. The systems use high-efficiency particulate air (HEPA/ULPA) filters, activated carbon-based filters with and without impregnation and/or activated alumina-based filters with impregnation. The maximum airflow of the systems ranges between 220 and 500 m3/h, depending on the filter configuration. The units were investigated under laboratory and simulated field conditions to determine removal efficiencies for various substances. High removal efficiencies for mercury vapour, formaldehyde, particles and microorganisms could be observed. The elimination of strong odours (orange oil, cinnamon oil and menthol) is difficult, if the source of the odour is not removed. The unit’s effectiveness in dental practices and in hospital treatment rooms will be analysed in follow-up studies including personal bio-monitoring investigations. The data will facilitate the evaluation of the role that optimised air purification systems can play in reducing pollutant exposure of medical personnel and patients.

Studies examining health consequences of the release of mercury from dental amalgams have concluded that there is insufficient mercury released from these restorations to cause a medical problem. Although the mercury vapor generated during removal of amalgams will cause a transient increase in the patient’s mercury level in tissue fluids, biochemical assays have demonstrated that the increase is too small to have a negative influence on organ systems. This is true even when patients have all their amalgams removed in a single session. Nevertheless, over the past decade, the release of mercury from dental amalgam has been frequently blamed for a variety of health complaints. A number of sensationalized media reports regarding the mercury issue have no doubt contributed to the public concern that has been aroused. Consequently, patients may present at the dentist’s office, either self-diagnosed or looking for a cause implicating mercury. In actuality, these patients may have symptoms of either medical problems or psychological disorders such as depression or anxiety. Unfortunately, the incorrect diagnosis may not only mislead, but actually place the patient in a dangerous situation. Two well-controlled studies have indicated that (1) 89% of the patients with self-reported “amalgam illness” had psychogenic disorders, whereas only 6% of the matched-pair manifested symptoms of these psychological disorders; and (2) these alleged “amalgam illness” patients had preneurotic reactive/defensive mechanisms that did not allow them to recognize aggressive and threatening situations which the control group would quickly and readily regard as potentially difficult to manage. Other studies involving psychological assessment seem to confirm that dental therapy (removal of amalgams) for people with alleged “amalgam illness” may, at best, provide a “placebo effect”.

“The interactions between the nervous and immune systems have been recognized in the development of neurodegenerative disease. This can be exploited through detection of the immune response to autoantigens in assessing the neurotoxicity of environmental chemicals. To test this hypothesis, the following questions were addressed. a) Are autoantibodies to nervous system (NS) antigens detected in populations exposed to environmental or occupational chemicals? In sera of male workers exposed to lead or mercury, autoantibodies, primarily IgG, to neuronal cytoskeletal proteins, neurofilaments (NFs), and myelin basic protein (MBP) were prevalent. These findings were confirmed in mice and rats exposed to either metal. b) Do autoantibodies to NS antigens relate to indices of exposure? In humans exposed to either metal, and similarly in exposed rats, titers of IgG against NFs and MBP significantly correlated with blood lead or urinary mercury, the typical indices of exposure. c) Do autoantibodies correlate with sensorimotor deficits? In workers exposed to lead or mercury, a significant correlation was observed between IgG titers and subclinical deficits. Doses of metals used in rat exposures were subclinical, suggesting that autoantibodies may be predictive of neurotoxicity. d) Is the detection indicative of nervous system pathology? In rats exposed to metals, histopathology indicated central nervous system (CNS) and peripheral nervous system (PNS) damage. In addition there was evidence of astrogliosis, which is indicative of neuronal damage in the CNS, and the presence of IgG concentrated along the blood-brain barrier, as indicated by immunostaining for antibodies. e) Are immune responses to NS antigens pathogenic? Immunoglobulin fractions from rat and human sera interfered with neuromuscular function. These studies suggest that the detection of autoantibodies to NS-specific antigens may be used to monitor the development of neurotoxicity to environmental chemicals and that immune mechanisms may be involved in the progression of neurodegeneration.”