Mercury

“A relationship between multiple sclerosis (MS) and dental silver-mercury fillings has been suggested by some investigators, but never proven. This study documents objective biochemical changes following the removal of these fillings along with other dental materials, utilizing a new health care model of multidisciplinary planning and treatment. The dramatic changes in photolabeling of cerebrospinal fluid (CSF) proteins following these dental interventions suggest CSF photolabeling may serve as an objective biomarker for monitoring MS. The clear-cut character of these changes should also encourage more research to better define this possible association between dental mercury and MS.”

“Intracellular calcium mobilization of isolated guinea pig cochlear outer hair cells (OHCs) was investigated using thimerosal, a -SH group oxidizing agent, and fura-2 fluorescence ratio imaging microscopy. In the presence of thimerosal, intracellular Ca2+ concentrations ([Ca2+]i) of OHCs were elevated in a dose-dependent manner. Even in Ca(2+)-free medium, Ca2+ response was still induced. The effects of thimerosal on [Ca2+]i were completely blocked and reversed by dithiothreiotol (DTT). Neither 1-100 microM ryanodine nor 5-20 mM caffeine altered the effects of thimerosal. Pretreatment with pertussis toxin (PTX) for 30 min did not affect the thimerosal-induced increase in [Ca2+]i. The increase in [Ca2+]i when Ca2+ was added during thimerosal application in Ca(2+)-free medium was almost completely blocked by 500 microM LaCl3, while nifedipine did not inhibit further increase in [Ca2+]i caused by thimerosal. Thus, oxidation of the -SH group of the OHC membrane can induce a Ca2+ release from intracellular Ca2+ stores, which are ryanodine- and caffeine-insensitive, and Ca2+ influx through non-specific Ca2+ channels, but not the nifedipine-sensitive Ca2+ channels. The possible oxidation of -SH group gated Ca2+ channels in OHCs is worthy of further study.”

“Alzheimer’s disease (AD) is a common neurodegenerative disorder that leads to dementia and death. In addition to several genetic parameters, various environmental factors may influence the risk of getting AD. In order to test whether blood levels of the heavy metal mercury are increased in AD, we measured blood mercury concentrations in AD patients (n = 33), and compared them to age-matched control patients with major depression (MD) (n = 45), as well as to an additional control group of patients with various non-psychiatric disorders (n = 65). Blood mercury levels were more than two-fold higher in AD patients as compared to both control groups (p = 0.0005, and p = 0.0000, respectively). In early onset AD patients (n = 13), blood mercury levels were almost three-fold higher as compared to controls (p = 0.0002, and p = 0.0000, respectively). These increases were unrelated to the patients’ dental status. Linear regression analysis of blood mercury concentrations and CSF levels of amyloid beta-peptide (A beta) revealed a significant correlation of these measures in AD patients (n = 15, r = 0.7440, p = 0.0015, Pearson type of correlation). These results demonstrate elevated blood levels of mercury in AD, and they suggest that this increase of mercury levels is associated with high CSF levels of A beta, whereas tau levels were unrelated. Possible explanations of increased blood mercury levels in AD include yet unidentified environmental sources or release from brain tissue with the advance in neuronal death.”

“Alzheimer’s disease (AD) brain trace-element imbalances in the amygdala, hippocampus and nucleus basalis of Meynert (nbM) are found in most cases to be consistent with those previously reported in samples derived principally from AD cerebral cortex (Ehmann et al., 1986). The elevation of mercury in AD nbM, as compared to age-matched controls, is the largest trace-element imbalance observed to date in AD brain. In addition to the general confirmation of imbalances for Cs, Hg, N, Na, P, and Rb noted previously in cerebral cortex samples, imbalances for Fe, K, Sc, and Zn were observed in two regions and one region also exhibited imbalances for both Co and Se. Persistent imbalances for the univalent cations Na, K, Rb and Cs support arguments for a membrane abnormality in AD. The data presented here also provide the first comprehensive simultaneous multi-element determinations in both control and AD nbM.”

“Possible adverse effects of mercury exposure in dentistry have been discussed in several studies. The objective of the present study was to carry out detailed measurements of mercury exposure in the dental profession in Sweden, and to search for adverse health effects from such exposure. We examined 22 dentists and 22 dental nurses, working in teams, at six Swedish dental clinics. Measurements of air mercury, performed with personal, active air samplers, showed a median air Hg of 1.8 micrograms/m3 for the dentists, and 2.1 micrograms/m3 for the dental nurses. Spot measurements with a direct reading instrument displayed temporarily elevated air Hg, especially during the preparation and application of amalgam. The average concentration of mercury in whole blood (B-Hg) was 18 nmol/L, in plasma (P-Hg) 5.1 nmol/L, and in urine (U-Hg) 3.0 nmol/mmol creatinine. Possible effects on the central nervous system (CNS) were registered with three questionnaires: Q16, Eysenck Personality Inventory (EPI), and the Profile of Mood Scales (POMS). In the Q16, the number of symptoms was statistically significantly higher in the dentistry group compared with an age- and gender-matched control group (n = 44). The urinary excretion of albumin and urinary activity of the tubular enzyme N-acetyl-beta-glucose-aminidase (NAG) did not differ between the two groups. The results confirm that exposure to mercury in the dental profession in Sweden is low. The air Hg levels were mainly influenced by the method of amalgam preparation and inserting, and by the method of air evacuation during drilling and polishing.”

“Advancements in materials development and in technologies may elicit new occupational hazards in the dental profession. Thus, the dentist should not become lax or complacent. Yet, once a potential adverse health effect is identified, steps are taken to rectify the situation. The field of dentistry is a relatively safe profession and, with proper knowledge and precautions, even those relatively few minor risks can be lessened or even eliminated.”

With present knowledge it is impossible to estimate the risk of effects on the foetal brain induced by the mother’s exposure to mercury from amalgam. Available facts, however, do not support a dismissal of the risk. Therefore treatment of children and women of childbearing age with amalgam should be avoided. It is also recommended that use of amalgam for dental restorations in the population in general is abandoned and substituted with less toxic material, whenever this is available and affordable.

Seven multiple sclerosis subjects had their silver dental fillings (amalgams) removed which contained approximately 50% mercury. A visual evoked response (VER) test was performed before amalgam removal. Approximately six months after amalgam removal a second VER test was performed on all subjects, and the latencies of the VER decreased significantly. The mean latency of P1 for the right and left eye combined decreased by 23.1 milliseconds (P = 0.011) and N1 for the right and left eye combined decreased by 23.1 milliseconds (P = 0.026). It was hypothesized that mercury from dental amalgam was an etiological factor in reduced nerve conduction velocity in MS subjects.

“This is the last in a series of articles on the future of dental amalgam. It considers possible alternative materials to amalgam for the restoration of posterior teeth. The materials discussed are gold inlays, gold foil, gallium alloys, and tooth coloured non-metal alternatives including glass-ionomer cements, composite resins, glass-ionomer-resin hybrids, compomers and ceramics. The clinical indications for these restorations are first described along with their potential clinical problems and their mean survival rates in comparison with dental amalgam. Secondly, the safety of composite resins is considered and potential toxic and hypersensitive effects of these materials are discussed. Finally, it is concluded that the present evidence does not appear to demonstrate that dental amalgam is hazardous to the health of the general population. It does, however, recommend that in continuing to use amalgam dentists must use strict mercury hygiene procedures to avoid risk to their staff and contamination of the environment. It seems that mercury contamination of the environment is likely to be the main reason for any future government action against the continued clinical use of dental amalgam.”

“The effect of exposure to inorganic mercury on the pregnant woman and her foetus has received little attention. Transport of elemental inorganic mercury into foetal tissues has been reported, and prior studies indicate a higher incidence of adverse pregnancy outcome. The effects of occupational exposure to inorganic mercury on pregnancy were investigated among 46 exposed women workers: controls were 19 women working in non-production areas of the same factory. There were 104 recorded total pregnancies during the period 1948-77. The study revealed a higher frequency of adverse reproductive outcomes, especially congenital anomalies, among the women exposed to inorganic mercury levels at or substantially lower than 0.6 mg/m3; no significant differences in the stillbirth or miscarriage rates were noted between the two groups of women. The overall foetal death rate in this study was similar to New York state (USA) and national levels for the same period.”