Neurotoxic effects of mercury exposure in dental personnel.

Numerous studies have reported neurobehavioural effects in dental personnel occupationally exposed to chronic low levels of mercury (Hg). Hg exposure from dental work may also induce various chronic conditions such as elevation of amyloid protein expression, deterioration of microtubules and increase or inhibition of transmitter release at motor nerve terminal endings. Therefore, clinical studies of Hg toxicity in dentistry may provide new knowledge about disturbed metal homeostasis in neurodegenerative diseases such as Alzheimer's disease, multiple sclerosis and mood disorders. The purpose of this MiniReview is to evaluate the evidence of possible relevance between Hg exposure in dentistry and idiopathic disturbances in motor functions, cognitive skills and affective reactions, as well as dose-response relationships.

Mercury exposure and its effects on fertility and pregnancy outcome.

Mercury (Hg), a highly toxic environmental pollutant, shows harmfulness which still represents a big concern for human health, including hazards to fertility and pregnancy outcome. Research has shown that Hg could induce impairments in the reproductive function, cellular deformation of the Leydig cells and the seminiferous tubules, and testicular degeneration as well as abnormal menstrual cycles. Some studies investigated spontaneous abortion and complicated fertility outcome due to occupational Hg exposure. Moreover, there is a relation between inhaled Hg vapour and reproductive outcome. This MiniReview evaluates the hypothesis that exposure to Hg may increase the risk of reduced fertility, spontaneous abortion and congenital deficits or abnormalities.

Changed clinical chemistry pattern in blood after removal of dental amalgam and other metal alloys supported by antioxidant therapy.

This study aimed to investigate a possible connection between removal of dental amalgam restorations supported by antioxidant therapy and indicative changes of clinical chemistry parameters. A group of 24 patients, referred for complaints related to amalgam restorations, underwent a removal of their amalgams. All patients were treated with antioxidants (vitamin B-complex, vitamin C, vitamin E, and sodium selenite). An age- and sex-matched control group of 22 individuals was also included. The mercury (Hg) and selenium (Se) concentration in plasma, Hg concentration in erythrocytes, and 17 clinical chemistry variables were examined in three groups: patients before amalgam removal (Before), patients after amalgam removal (After), and control individuals (Control). The Hg and Se values decreased (p < 0.05) in plasma, and the Hg concentration decreased (p < 0.05) in erythrocytes after amalgam removal. The variables serum lactate dehydrogenase (serum LDH) and serum sodium differed significantly both when comparing Control with Before (p < 0.01) and Before with After (p < 0.01). The variables white blood cell count (WBC), blood neutrophil count, blood eosinophil count, blood basophil count, blood lymphocyte count, blood monocyte count, serum potassium, and serum creatinine differed in the Before/After test (p < 0.05). Multivariate statistics (discriminant function analysis) could separate the groups Before and After with only one misclassification.

Arsenic is decreased in target organs during viral infection in mice.

Arsenic (As), a potentially toxic trace element, has been shown to influence viral replication and resistance to microbial infection. However, the impact of infection on the normal As status in target organs involved in the disease process has not been studied to date. In the present study, As was measured through inductively coupled plasma mass spectrometry in the plasma, liver, spleen, kidney, heart, pancreas and brain at days 1 and 3 of coxsackievirus B3 infection in female Balb/c mice. The severity of the infection was assessed from clinical signs of disease. The infection changed plasma As in a biphasic pattern with a small increase (n.s.) at day 1 that turned into a decreasing trend (13%, p<0.05) by day 3. In the liver, spleen, heart, pancreas and kidney As was unchanged at day 1 but, at day 3, it had decreased by 71% (p<0.01), 64% (p<0.01), 55% (p<0.01), 63% (p<0.01) and 73% (p<0.01), respectively. In the brain, As went unchanged. The pathophysiological interpretation of these findings requires further research.

Mercury recovery in situ of four different dental amalgam separators.

Amalgam separators are used to physically remove dental amalgam from waste water in dental clinics. They are thereby supposed to reduce mercury (Hg) emissions to the municipal waste water system to acceptable levels. We here present results from a comparative study in situ of three amalgam separators available on the market, all with a claimed efficiency of 99% according to Danish and ISO protocols, and using sedimentation as the principle of separation. We also present corresponding data for an investigational prototype of an improved separator. The obtained efficiency of the three commercial separators is far below what is stated by the manufacturer and by authorities assumed to be the efficiency in clinical conditions. They reduced Hg emissions by 79 - 91%, leaving an average Hg content in outgoing waste water of 1.5 mg L(-1). However, the prototype separator participating in this study retained 99.9% of the waste water Hg emissions, leaving an average Hg content in outgoing waste water of 0.004 mg L(-1). Physical restrictions prohibit sedimentary type separators to recover the Hg fractions causing the largest damages in wastewater treatment plants. This fraction is not considered in the ISO protocol for testing amalgam separators, which therefore needs to be revised. Abolishing the use of dental amalgam and cleaning the tubing systems is the most efficient long-term solution to reduce Hg emissions from dental clinics. Until then, Hg emissions originating from placing, polishing or removing existing amalgam fillings, should be counteracted by the use of low-emission amalgam separators, already on the market or presently being developed for use alone or together with sedimentary type amalgam separators.

Metal-specific lymphocyte reactivity is downregulated after dental metal replacement.

OBJECTIVES: This study was done to evaluate the results and clinical relevance of an optimized lymphocyte proliferation test, MELISA, for metal-induced inflammation in patients with CFS-like symptoms. The treatment of patients consisted of the replacement of incompatible dental materials (RID) together with supportive anti-oxidant therapy. DESIGN OF THE STUDY: 513 patients were tested by MELISA at the beginning of the study. Out of this group, 248 patients were available for follow-up MELISA after RID. METHODS: In MELISA, lymphocytes are isolated from the blood and cultivated with different metal salts in tissue culture medium containing 10% inactivated human AB+ serum or autologous serum. After 5 days, the presence of metal-reactive lymphocytes are measured by isotope labelling of newly formed DNA in growing lymphoblasts and evaluated by calculating the Stimulation Index. RESULTS: Nickel was the most common sensitizer, followed by inorganic mercury, thimerosal, lead, cadmium, palladium and gold. After RID treatment, a decrease of metal-specific lymphocyte responses in patients who reacted to metals at the beginning of the study could be observed. The cultivation of lymphocytes in autologous and homologous serum did not significantly affect the results. Simultaneous, the health status of patients improved as well. CONCLUSIONS: Replacement of incompatible dental materials resulted in down-regulation of metal-induced lymphocyte sensitivity in vitro, as well as in the improvement of health status of majority of patients with unspecific CFS-like symptoms.

Decrease of trace elements in erythrocytes and plasma after removal of dental amalgam and other metal alloys.

The objective of this study was to determine the concentration changes of 13 elements in erythrocytes and plasma after the removal of dental amalgam and other metal alloys. Blood samples from 250 patients were collected, separated into erythrocytes and plasma, and analyzed by inductively coupled plasma-mass spectrometry. The 250 patients were divided into 3 groups (Negative, Zero, and Positive) depending on their estimation of quality of life in an earlier study. Magnesium in plasma, selenium and mercury in plasma, and erythrocytes showed decreased concentrations after amalgam removal in all groups (p < 0.05). Titanium in plasma, copper in plasma, and erythrocytes and zinc in plasma exhibited decreased concentrations after amalgam removal in the Negative and Positive groups (p < 0.05). Silver in plasma and gold in erythrocytes decreased in the Zero and Positive groups after amalgam removal (p < 0.05). Copper in erythrocytes and silver and gold in plasma showed higher concentrations after amalgam removal in the Negative compared to the Positive group (p < 0.05), suggesting that patients in the Negative group excrete metals slowly. Moreover, the cobalt levels in plasma were lowest in the Negative group and only this group showed a significant increase in vitamin B12 levels in blood after amalgam removal.

Selenium and mercury are redistributed to the brain during viral infection in mice.

As part of the general host response to coxsackievirus B3 (CB3) infection, the concentration of essential and nonessential trace elements changes in different target organs of the infection. Essential (e.g., Se) and nonessential (e.g., Hg) trace elements are known to interact and affect inflammatory tissue lesions induced by CB3 infection. However, it is unknown whether these changes involve the brain. In the present study, the brain Hg and Se contents were measured through inductively coupled plasma-mass spectrometry and their distribution investigated by means of nuclear microscopy in the early phase (d 3) of CB3 infection in normally fed female Balb/c mice. Because of the infection, the concentration of Hg (4.07 +/- 0.46 ng/g wet wt) and Se (340 +/- 16 ng/g wet wt) in the brain increased twofold for Hg (8.77 +/- 1.65 ng/g wet wt, p < 0.05) and by 36% for Se (461 +/- 150 ng/g wet wt, ns). Nuclear microscopy of brain sections from mice having elevated Se and Hg concentrations failed to find localized levels of the elements high enough to make detection possible, indicating approximately homogeneous tissue distribution. Although the pathophysiological interpretation of these findings requires further research, the increase of Hg in the brain during infection might have an influence on the pathogenesis of the disease.

Effects of a superantigen-antibody recombinant fusion protein (r-C242 Fab-SEA) on toxicological responses in the anaesthetised rabbit.

The objective was to study toxin-induced effects on physiological parameters in the rabbit and whether these parameters show dose-response and co-variation after administration of a recombinant fusion protein between staphylococcal enterotoxin (SE) and the Fab fragment of an antibody. Rabbits are very sensitive to SE toxins and the cardiovascular and immune effects are similar to those observed in septic shock in man. The test compound, r-C242 Fab-SEA, was administered intravenously to anaesthetised New Zealand white rabbits at doses in the range of 0.00005-50 microg/kg. All rabbits were checked for titres of anti-SEA antibodies before entering the experiment, since they could neutralise the effect of the test compound. Heart rate, blood pressure and body temperature were continuously monitored before and during 6 h after dosing. Immediately before the start of administration and 3 and 6 h during the experiment, blood gases (pO(2) and pCO(2)), pH, haematology, clinical chemistry, cytokine response (TNF-alpha) and trace elements (Mn, Cu, Zn, Se, Ag, Cd, Hg and Pb) were measured. No mortality occurred, but at 50 microg/kg severe adverse clinical signs developed. The decrease in blood pressure was weakly dose-related. Heart rate, ECG, body temperature, pCO(2) and pH were not affected by the treatment. pO(2) tended to increase as a function of time, but not in relation to dose. WBC and PLT decreased dose dependently. TNF-alpha was not affected by the treatment. The major effects on clinical chemistry were a dose-dependent increase in AST and creatinine. Potassium and urea showed dose dependent increases, mainly at higher doses, though these changes were of less value for drug selection purposes. Trace element changes were observed, including an increase in Mn and a decrease of Zn at all doses. The Cu/Zn ratio decreased below normal at low doses, whereas at high doses in which adverse effects developed, it increased above normal. Post mortem examination revealed minimal to moderate dose-related granulocytic infiltrate in the lungs. The present study showed dose-response and co-variation between several changes in cardiovascular, haematology, clinical chemistry and trace element parameters during the initial phase of toxin-induced effects preceding a possible lethal endpoint and associated patho-physiological changes.

Metallothionein is induced and trace element balance changed in target organs of a common viral infection.

In experimental studies on the common human coxsackievirus B type 3 (CB3) infection, administered cadmium (Cd) is known to accumulate in the liver and kidneys. CB3 adapted to Balb/c mice was used to study whether infection affects the Cd-binding protein, metallothionein (MT) and if this alters the normal physiological trace element balance in the liver, kidney, spleen and brain. On day 3 of infection, degradation of liver proteins (44%, P<0.01) occurred, whereas in the spleen, protein increased (63%, P<0.05). The infection increased MT five-fold (P<0.01) in liver and kidneys, and in spleen by 34% (P<0.05). A redistribution of Cd and copper (Cu) from the liver to the kidney was associated with this increase in MT, resulting in an increased (P<0.01) kidney/liver ratio for both elements. The infection increased the zinc (Zn) concentration more in the kidney than in the liver, but the kidney/liver ratio was not significantly affected. Results show that MT is increased in several organs during the early phase of infection and is associated with redistribution of both essential and non-essential trace elements. This may be a normal response in common infections that could adversely influence the pathogenesis when the host is concomitantly exposed to potentially toxic trace elements, even at levels in the physiological range.

Indications of selenium protection against cadmium toxicity in cultured K-562 cells.

The interaction between selenium and cadmium was studied in relation to cellular uptake and expressions of selenium-cadmium interaction. Human K-562 cells were pre-treated or simultaneously treated with (5 or 50 microM) selenite or (10 or 50 microM) selenomethionine and with (60 or 75 microM) cadmium nitrate. Cells pre or simultaneously treated with selenite revealed increased cadmium concentration with increased doses of selenite, particularly pronounced in the simultaneous treatments. In both treatments, selenium protection was observed during the exposure period, but not during the growth period. In cells simultaneously treated with selenomethionine and 60-microM cadmium, an increase in cadmium concentration was observed after increased selenium dose. In addition, it was found that simultaneous selenomethionine treatment with 60-microM cadmium resulted in selenium protection during the exposure period, although protection was not observed during the growth period.

Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on trace elements, inflammation and viral clearance in the myocardium during coxsackievirus B3 infection in mice.

A myocarditic coxsackievirus B3 (CB3) infection in adult male A/J mice was used to investigate the effects of 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) exposure on mortality and on inflammatory lesion, virus and trace element contents of the heart. The mice were injected with four weekly intraperitoneal (i.p.) injections of TCDD (a loading dose of 5 microg/kg followed by three maintenance doses of 1.4 microg/kg). To reach a steady-state body burden of TCDD the mice were allowed a 90-day recovery period before infection with CB3 virus. TCDD increased the infection-induced mortality rate, whereas in TCDD-exposed mice, heart lesions at day 7 after the virus inoculation (median value 0.67% of the tissue section area; interquartile range 0.28; not statistically significant) were one-third of that in non-exposed infected mice (2.07% of the tissue section area; interquartile range 3.06). The size of the inflammatory heart lesion correlated to the amount of virus (r(s) = 0.829, P < 0.01) as well as to the calcium (Ca: r(s) = 0.725, P < 0.01) and the magnesium (Mg: r(s) = -0.615, P < 0.05) contents. In TCDD-exposed mice in situ hybridisation of viral RNA in the myocardium at day 7 showed a tendency to decreased amounts of virus, as well as a less pronounced increase in myocardial Ca content, both supporting a milder myocardial disease after TCDD exposure. No effect of TCDD exposure was seen on the zinc (Zn) or selenium (Se) levels in the myocardium. In conclusion, although TCDD seemed to have a limiting effect on viral replication and the development of the inflammatory lesion in the myocardium, mortality was increased by TCDD in this infection model. However, TCDD had no significant effects on the selected trace elements that could be of importance for the severity of the inflammatory lesion (Ca, Se), for the local host response activation (Zn) or for the development of myocardial disease complications (Mg). Accordingly, the increased mortality may be a result of an infection-induced increase in TCDD toxicity to vital organs other than the heart, and/or a TCDD-induced change in the tissue affinity and virulence of the virus, possibly causing involvement of other target organs in the infectious process and changed pathogenesis.

Removal of dental amalgam and other metal alloys supported by antioxidant therapy alleviates symptoms and improves quality of life in patients with amalgam-associated ill health.

OBJECTIVES: The purpose of this study was to evaluate treatment of patients suffering from chronic ill health with a multitude of symptoms associated with metal exposure from dental amalgam and other metal alloys. SETTING AND DESIGN: We included 796 patients in a retrospective study using a questionnaire about symptom changes, changes in quality of life as a consequence of treatment and assessment of care taking. METHODS: Treatment of the patients by removal of offending dental metals and concomitant antioxidant therapy was implemented according to the Uppsala model based on a close co-operation between physicians and dentists. RESULTS: More than 70% of the responders, remaining after exclusion of those who had not begun or completed removal, reported substantial recovery and increased quality of life. Comparison with similar studies showed accordance of the main results. Plasma concentrations of mercury before and after treatment supported the metal exposure to be causative for the ill health. MAIN FINDINGS: Treatment according to the Uppsala model proved to be adequate for more than 70% of the patients. Patients with a high probability to respond successfully to current therapy might be detected by symptom profiles before treatment. CONCLUSIONS: The hypothesis that metal exposure from dental amalgam can cause ill health in a susceptible part of the exposed population was supported. Further research is warranted to develop laboratory tests to support identification of the group of patients responding to current therapy as well as to find out causes of problems in the group with no or negative results.

Metal-specific lymphocytes: biomarkers of sensitivity in man.

Many patients attribute their health problems to amalgam and other dental metals. In genetically susceptible indviduals, mercury and gold may function as haptens and elicit allergic and autoimmune reactions. The frequency of metal-induced lymphocyte responses was examined in 3,162 patients in three European laboratories using MELISA(R), an optimized lymphocyte proliferation test. The patients suffered from local and systemic symptoms attributed to dental restorations. The effect of dental metal removal was studied in 111 patients with metal hypersensitivity and symptoms resembling Chronic Fatigue Syndrome (CFS). After consultation with a dentist the patients decided to replace their metal restorations with non-metallic materials. The changes in health and in vitro lymphocyte reactivity were studied by inquiries and follow-up MELISA(R). Lymphocyte reactivity was also analyzed in 116 healthy subjects with no complaints of metal allergy. A significant number of patients had metal-specific lymphocytes in the blood. Nickel was the most common sensitizer, followed by inorganic mercury, gold, phenylmercury, cadmium and palladium. As compared to lymphocyte responses in healthy subjects, the CFS group had significantly increased responses to several metals, especially to inorganic mercury, phenylmercury and gold. Following dental metal removal, 83 patients (76%) reported long-term health improvement. Twenty-four patients (22%) reported unchanged health and two (2%) reported worsening of symptoms. Following dental metal replacement, the lymphocyte reactivity to metals decreased as well. We propose that an inflammatory process induced by metals may modulate the hypothalamic-pituitary-adrenal axis (HPA axis) and trigger multiple non-specific symptoms characterizing CFS and other chronic conditions like myalgic encephalitis (ME) and multiple chemical sensitivity (MCS).

Selenium protection against mercury-induced apoptosis and growth inhibition in cultured K-562 cells.

Selenium and mercuric chloride (MC) interactions regarding effects on cell growth and cell death have been studied. Human K-562 cells were pretreated or simultaneously treated with either selenite (5 or 50 microM) or selenomethionine (10 or 50 microM) and with MC (35 or 50 microM). The 35-microM MC treatments resulted in a clear inhibition of cell growth with no obvious difference between mercury-treated and mercury-selenium-treated cells. Furthermore, the apoptotic frequency was similar at all observations for all selenium treatments with 35 microM MC. In the simultaneously treated selenite and 50- microM MC combinations, a selenite-dependent protection was shown both by increased cell growth and by lower apoptotic frequency at 48 and 96 h of exposure. Both treatments with selenomethionine showed protection observed as an increased cell growth at 48 and 96 h and as decreased apoptotic frequency at 96 h of exposure.

Sequential changes in Fe, Cu, and Zn in target organs during early Coxsackievirus B3 infection in mice.

In Coxsackievirus B3 (CB3) infection, the heart and pancreas are major target organs and, as a general host response, an associated immune activation and acute phase reaction develops. Although iron (Fe), copper (Cu), and zinc (Zn) are involved in these responses, sequential trace element changes in different target organs of infection have not been studied to date. In the present study, Fe, Cu, and Zn were measured through inductively coupled plasma mass spectrometry (ICP-MS) in the plasma, liver, spleen, heart, and pancreas during the early phase (d 1 and 3) of CB3 infection in female Balb/c mice. The severity of the infection was assessed through clinical signs of disease and histopathology of the heart and pancreas, including staining of CD4 and CD8 cells in the pancreas. During infection, the concentrations of Fe, Cu, and Zn changed in the plasma, liver, and pancreas, but not in the spleen and heart. The changes in plasma Cu, Zn, and Fe seemed to be biphasic with a decrease at d 1 that turned into increased levels by d 3. Cu showed similar biphasic changes in the liver, spleen, and pancreas, whereas, for Zn and Fe, this pattern was only evident in the liver. In the pancreas, the reverse response occurred with pronounced decreases in Fe (23%, p < 0.05) and Zn (64%, p < 0.01) at d 3. Although the pathophysiological interpretation of these findings requires further research, the sequential determination of these elements may be of clinical value in enterovirus infections in deciding the stage of disease development.

Trace element changes in sclerotic heart valves from patients undergoing aortic valve surgery.

Several trace elements are essential nutrients for an optimal functioning of organs and tissues, including the immune system and the heart. The pathogenesis of some heart diseases has been associated with changes in the balance of certain trace elements. The etiology of nonrheumatic aortic valve sclerosis is unknown, however. A prospective study was performed on trace element changes in the sclerotic valves of 46 patients undergoing surgical aortic valve replacement because of aortic stenosis. Valves from 15 individual forensic cases without known cardiac disease served as controls. The contents of 15 trace elements (Al, As, Cd, Ca, Co, Cu, Fe, Pb, Mg, Mn, Hg, Se, Ag, V, and Zn) were measured by inductively coupled plasma - mass spectrometry (ICP-MS) of aortic valve tissue from both patients and forensic autopsy controls. Some trace elements showed similar concentrations in sclerotic and control valves (Al, Ag, Hg, Mn), whereas a few were moderately changed in the sclerotic as compared with the control valves, including an increase in Cd by 52% (p < 0.05) and decreases in Se by 14% (p < 0.05), in V by 42% (p < 0,001), and in Cu by 45% (p < 0.001). However, there were pronounced increases (p < 0.001) in the concentrations of As (5-fold), Ca (70-fold), Co(10-fold), Fe (20-fold), Pb (8-fold), Mg (20-fold), and Zn (10-fold) in the sclerotic valves. Thus, sclerotic aortic valve disease is associated with a pronounced imbalance in several trace elements of well-known importance for cardiovascular and immune function as well as in trace elements with hitherto unknown significance.

Interactions between Chlamydia pneumoniae and trace elements: a possible link to aortic valve sclerosis.

An association between Chlamydia pneumoniae and atherosclerotic cardiovascular diseases has been suggested. However, other factors may interact in the pathogenesis of valve sclerosis. Therefore, trace elements important for C. pneumoniae growth and host defense and markers of C. pneumoniae infection were studied in sclerotic valves and serum. Forty-six patients undergoing surgical valve replacement due to advanced aortic sclerosis were prospectively studied. Valves from 15 forensic cases with no heart valve disease and plasma from 46 healthy volunteers served as controls. C. pneumoniae was detected in 16/46 (34.8 %) sclerotic valves and in 0/15 forensic controls. IgG and IgA antibodies to C. pneumoniae were present in 54.3% and 26.1 % patients, respectively. In the patients' valves, iron, magnesium, and zinc each correlated to calcium, a marker of the histopathological severity of disease. Patients showed 10- to 70-fold increases of these trace elements in valves and an increased copper/zinc ratio in serum. In a majority of aortic sclerosis patients, one of several markers of C. pneumoniae infection were detected and all patients had a disturbed trace element balance in valves and serum suggestive of active immune process and infection. The pattern of trace element changes was essentially similar regardless of positive makers of C. pneumoniae, suggesting a similar etiopathogenesis in both subgroups. The 20-fold increase in iron, essential for C. pneumoniae growth, in sclerotic valves suggests a new possible link to this infection in aortic sclerosis.