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“With regard to the principal purpose of this investigation, it is apparent that exposure to mercury during the preparation of silver amalgam definitely presents an additional occupational hazard as an allergen in the dentist. The fact that the dental students who were the volunteers in this study received only a small fraction of the exposure to mercury that the practicing dentist receives does emphasize the potential of this allergen in actual dental practice. Recent publicity concerning the toxioogenicity of mercury has led to a call for improved mercury hygiene in the dental operatory. The allergenic potential of mercury, as reported in this paper, accentuates the need for such an improvement.”

“Under the conditions of this study, systemically or topically applied thimerosal was found to have no teratogenic effect even when given in concentrations approaching the 50% lethal dose of these compounds. A comparison of topical and subcutaneous administration of thimerosal to rabbits shows that a substantial concentration of mercury was present in blood and tissues of the treated animals and their offspring. Thimerosal was found to cross the blood-brain and placenta barriers.”

“Experimental use of primary cultures of endocrine pancreas is constrained by early, vigorous proliferation of fibroblastoid cells. The addition of heavy metals, sodium ethylmercurithiosalicylate, phenyl mercuric acetate, phenyl mercuric nitrate and sodium aurothiomalate to the culture media selectively destroys these fibroblastoid cells yielding highly enriched, morphologically intact, functionally competent endocrine cells that are capable of cell replication. This action of heavy metals appears to be due to reversible inhibition of sulfhydryl enzymes since glutathione and thioglycolate were demonstrated to completely inhibit the cytotoxic effects of the mercury and gold containing agents, respectively. Certain variables in the application of the mercurial agents to pancreatic endocrine cell cultures were defined, most notably the enhanced sensitivity of fetal vs. neonatal tissue, and in inverse relationship of cell density to effective toxicity. After removal of the heavy metal agent from the culture media, many pancreatic islets send out cytoplasmic projections, containing large numbers of oriented microtubules which serve as bridging units to adjacent endocrine cells. The sustained availability of virtually pure pancreatic endocrine cell cultures, which results from the application of mercury to the culture media will undoubtedly permit many aspects of the cell biology of the endocrine pancreas to be directly and sequentially assailed.”

“Clinical factors affecting residual mercury and marginal adaptations of amalgam restorations in a private practice environment were investigated. Findings, converted to ridit values, indicated that influencing factors are the training level of the dental assistants, type of amalgamator, accuracy of the timing device, and method of condensation.”

“Squirrel monkeys were dosed intranasally with saline or thiomersal (sodium ethylmercurithiosalicylate, 0.002 percent w/v) daily for six months. The total amounts of thiomersal given during the six months period were 418 mug (low dose group) and 2280 mug (high dose group). This was equivalent to 207 and 1125 mug mercury. The dose differential was achieved by more frequent administration to the high dose group. Mercury concentrations were significantly raised over control values in brain (high dose group only), liver, muscle and kidney, but not in blood. Concentrations were highest in the kidney, moderate in liver and lowest in brain and muscle. Much of the mercury was present in the inorganic form (37-91 percent). No evidence of toxicity due to thiomersal was seen in any animal. Nevertheless accumulation of mercury from chronic use of thiomersal-preserved medicines is viewed as a potential health hazard for man.”

“Silver and copper amalgams show a pronounced cytotoxic effect on monolayer cultures of human epithelial cells (NCTG 2544). Analyses of the medium from silver amalgam cultures showed that, zinc was released in substantial amounts (14 µg/ml after incubation for 24 h). Small amounts of mercury and possibly also some silver were released, whereas release of copper and tin could not be. detected. Toxicity tests showed that 10 µg Zn2+/ml reduced the number of cells by 96% after incubation for 24 h. In the copper amalgam cultures about. 100 µg copper and 5 µg, cadmium per ml medium were found after 24 h. Only small amounts of mercury were released, Toxicity tests showed an increasing effect of Cu2+ and Cd2+ with tune. With 50 µg Cu2+/ml the number of cells was reduced by 73% after incubation for 24 h, and after 3 d a similar effect was found with 25 µg/ml. With 10 ?g Cd2+/ml no cells were left after 24 h, whereas after 3 d 1µg/ml reduced cell growth by more than 80 %.”

“The mercury and silver content in gingival tissues in contact with class V silver amalgam fillings and in gingival tissues in contact with intact tooth enamel was studied in seven patients. The mercury content was determined by flameless atomic absorption spectrophotometry (Coleman Mas 50) and the silver content by atomic absorption (Perkin Elmer 303) at 3281 A. The results showed that biopsies from gingival tissues in contact with amalgam restorations had a markedly higher mercury content than control biopsies. Further studies will be performed.”

“Absorbed as well as backscattered electron-images of polished amalgam sections taken from extracted teeth have proved that silver-tin fillings undergo mercury losses in the marginal layer under conditions existing in the mouth.  There is evidence for the hypothesis that the lost mercury is partly vapourized and inhales.  Swallowing of ionized mercury derived from dental fillings also seems possible.  In both cases biochemical interactions and pathological effects might be expected and could add to those derived from environmental mercury and other toxic agents.”

“The authors cannot at this time state how much is absorbed by a patient under varying conditions or positively state that this rat study is comparable to humans. However, the authors wish to point out the possible dangers of exposure to mercury even in minute quantities that might occur in the dental practice.”

“It has been well documented that many of the metals compromise the immune system of experimental animals. Damage may occur to a particular cell (8, T, or macrophage) or may involve more than one cell which regulates the proliferation and differentiation of other cells responsible for normal function of the immune system. Preliminary studies are often necessary to ascertain if the chemicals actually alter antibody response to a particular antigen.”