Mercury

“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.”

Due to the difference in open circuit potential (OCP) versus SCE for Aristaloy amalgam (-969 mV) and Dispersalloy amalgam (-549 mV) in Ringer’s solution at 25 degrees C, a galvanic cell was created with Dispersalloy amalgam as cathode and Aristaloy amalgam as anode. The galvanic corrosion current was studied as a function of time for the above cell as well as for a cell of type III dental gold (OCP is +0-5 mV) versus Aristaloy amalgam. The initial corrosion current of the latter cell (105 micronA) is about twice that for the cell of Aristaloy amalgam versus Dispersalloy amalgam (54 micronA), however, their passivating behaviour is quite similar. Also, an interrupted galvanic corrosion test simulating the oral ‘make and break’ situation was performed. A much higher corrosion current than the steady state was found when the two electrodes resumed contact.

“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.”

An unreported spillage of mercury in a dental surgery resulting in four non-fatal cases of mercury intoxication by inhalation of mercury vapour is described and clinical symptoms in relation to urine mercury levels noted and discussed. The method of detection and decontamination of the mercury vapour source is reported, and suggestions for preventing spillage of mercury and for reducing the risk of intoxication from such accidental spillage are made.  Continued vigilance by all persons handling mercury is stressed.

“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.”