iaomtlibrary

“Mercury vapor levels associated with grinding amalgam models and mulling amalgams in the palm of the hand following trituration have been measured in a dental laboratory in inhalation position. The threshold limit value of airborne mercury of 0.05 mg/m3 was essentially exceeded in the grinding procedure of amalgam. Levels in excess of seven times this value were recorded. During mulling the mercury vapor level fluctuated around the threshold limit value. The mean mercury concentrations did not essentially exceed the threshold limit value.”

“A microbial fluctuation test, modified for the detection of environmental mutagens has been evaluated using a number of strains of the yeast Saccharomyces cerevisiae. Auxotrophic diploid cultures of yeast which produce prototrophic colonies by both mitotic gene conversion and mutation have been extensively utilized for the detection and evaluation of chemicals showing genetic activity. A number of the yeast strains utilized were shown to be suitable for use in the fluctuation test although the time scales of the experiments were considerably extended (up to 16 days) compared to those involving bacteria. The yeast strains respond to doses of mutagens at least a 100-fold lower than that required in a conventional short exposure treat and plate experiment. In experiments involving the induction of mitotic gene conversion at the tryptophan-5 and histidine-4 loci in the fluctuation test significant increases in prototrophic cells were produced in the presence of the insecticide Lindex (0.05 microng/ml), the preservative Thiomersal (0.0001 microng/ml), a mahogany hair dye (0.01 microng/ml), the herbicide Paraquat (0.02 microng/ml) and the alkylating agent ethyl methane sulphonate (0.1 microng/ml). The results demonstrate that the fluctuation test provides an extremely sensitive assay for the detection of chemicals which show genetic activity in yeast at non-toxic concentrations.”

“Based on an extensive literature search, general principles of mercury toxicity are outlined with respect to human individuals and populations. For the metal itself, as well as for its most important inorganic and organic compounds, the review discussed behavior in the body, characteristic clinical pictures, assessment of threshold levels, and evaluation as potential environmental hazards. Particular emphasis is placed on those diagnostic signs and symptoms which furnish early warning signals, permitting detection and elimination of overexposures.”

“Samples of fresh and fixed tissues from infants with exomphalos treated by thiomersal application were analysed for mercury content. The results showed that thiomersal can induce blood and organ levels of organic mercury which are well in excess of the minimum toxic level in adults and fetuses. The analysis of fresh and fixed tissues must be carefully controlled against normal tissues in order to interpret mercury levels accurately.”

“Finally, thiomersal, on the basis of extremely limited numbers (56 exposures) was associated with malformations overall, and with uniform malformations.”

“We present the results of an inquiry about the hydrargyric risk run by the staff of an odonto-stomatological laboratory. A second laboratory in which mercury was not used, served as a control. It would appear that the staff in the laboratory where the practician uses amalgam have a level of mercury higher than that of the staff working in the control laboratory. This level reaches the maximum in the middle of the day and returns to the same level as that of the controls after the nights rest outside the polluted atmosphere. These results are discussed in the light of our findings and of facts obtained from literature.”

“This paper reviews the reported cases of mercury poisoning in pregnancy and the data based on sources of contamination, maternal uptake, and distribution. It analyzes current knowledge of placental transfer of various mercury compounds, fetal uptake, and distribution. It identifies the embryopathic and fetal toxic effects of mercury in general while emphasizing the greater toxicity of methylmercury compounds. Since maternal exposure to methylmercury is primarily through fish consumption, it recommends that women of childbearing age should not consume more than 350 Gm. of fish per week. In addition, they should not be occupationally exposed to air concentrations of mercury vapor greater than 0.01 mg. per cubic meter, of inorganic and phenylmercuric compounds greater than 0.02 mg. per cubic meter, or any detectable concentration of methylmercury.”

“Using three independent criteria, we have found that 10?4-10?6M concentrations of ions presumably liberated from the corrosion of dental amalgam produce injurious effects on either human gingival fibroblasts or HeLa cells when the cells are grown in culture. Release of 51Cr and uptake of trypan blue dye were seen with 10-5M Hg++ and Ag+. Inhibition of amino acid incorporation into protein-like material was seen with eluates of amalgam and with ionic solutions of most metals comprising dental amalgam. Stannous ion showed little if any cytotoxic potential. These results suggest that corrosion products of amalgam are capable of causing cellular injury or destruction.”

“Amalgam has proved to be among the most versatile and durable of all restorative materials used in the treatment of dental disease. If it is handled and controlled properly, problems with its use should not develop. Safe mercury vapor levels can be maintained if good mercury hygiene practices are exercised. Materials and devices are available for aiding the dentist in adequate mercury control procedures. With the cooperation of each member of the dental team, compliance with all the criteria imposed by governmental regulatory agencies can be accomplished. These criteria have been established for the health protection of the dentist and his auxiliary personnel. Each practioner and office staff member should realize the potential hazards associated with mercury, and effect good mercury hygienic measures and control procedures.”