Mercury

A study was conducted to scrutinize the precision of a method for in vivo potential and polarization measurements. The variation with time of the magnitude of currents created at contacts between metallic dental restorations of varying age was also studied. The precision found indicates that the method allows for comparatively precise measurements of potentials to be taken. Studies of performed measurements of polarizations show that the precision of these measurements varies somewhat with contact conditions and the areas of restorations examined. The precision of the currents calculated was found sufficient for precise enough calculation to be made of the magnitude of currents created in the oral cavity. The study also shows a decrease with time of the magnitude of currents created at contact between metallic dental restorations of varying age.

An epidemiological study was performed in 250 persons who five years previously had been treated with extensive metallic reconstructions. To gain representative information these persons were selected at random from three Local Social Insurance Offices in different parts of Sweden. Those person, who in a questionnaire reported symptoms that could be alleged to have been caused by oral galvanic actions, were offered free clinical examination including quality evaluation and free measurements of potentials and polarizations of the metallic dental restorations. Persons from a subgroup to this study not suffering from any oral discomforts were chosen as a control group. Comparisons between the two groups were made in regard to current creation at metallic contacts, clinical quality and mucosal conditions. In none of the statistical analyses performed, differences could be shown between the groups. A tendency to higher amounts of restorative care at comparatively lower level of technical quality could, however, be noticed in the group of persons with oral symptoms which they themselves associated with oral galvanism.

Amalgam is still one of the most useful and widely used dental filling materials. On rare occasions however allergy to one of its constituents may preclude its use. In such instances confirmation is required so that an appropriate treatment plan may be formulated and submitted (if necessary) to the Dental Estimates Board (DEB) for approval.

“Different batches of the same preparation manufactured at the same enterprise, or at different enterprises, in accordance with the same manufacturing regulations have been found to be capable of producing a damaging effect of different intensity on the continuous cell culture L132. The titers vary, according to their cytotoxic effect, from 1 : 32 to 1 :2048. The components of B. pertussis antigens and thimerosal solutions have been found to produce the most pronounced cytotoxic effect on the cells. The comparison of the results of the titration of adsorbed DPT vaccine in cell cultures with clinical manifestations has shown correlation between a greater degree of cell damage in vitro and severe local reaction. Therefore, in the process of the quality control of preparations cell cultures provide more sensitive tests than laboratory animals, which is confirmed by our data obtained in revealing the toxic properties of adsorbed DPT vaccine and its components.”

“Metallic compounds have been shown to contribute to environmental pollution. They are potential health hazards, and many cause neuropathies in man and animals. Their cytotoxic properties were investigated in an isolated cell system by exposing 11-day-old chick embryonic nervous tissues to various concentrations of the metallic compounds. Following a 72 h incubation period at 37°C, phase contrast and light microscopic observations were made on cellular growth (nerve fibres, neuroglia, cell bodies) and cellular migration, for abnormalities. Results indicated that all cell growth inhibition was dosedependent with its magnitude (to produce a half-maximal effect) ranging from severely toxic (10^-6m or less) for Hg²⁺, Cd²⁺, As³⁺, and Vendex-Sn²⁺; moderately toxic (10^-4 to 10^-6m) for Tl¹⁺, As⁵⁺, Se⁴⁺, and Cu²⁺, and slightly toxic (10^-4 or greater) for Pb²⁺, As³⁺ (oxide), and Sn²⁺ (oxide). In all instances nerve fibres were more sensitive to metallic compounds than were neuroglia and cells. Subtoxic doses of some compounds caused increased neurite extension while others produced vacuolization. Other abnormalities included increased glial cell varicosities, granulation, decreased cellular migration and degenerative effects, especially at higher exposure levels. No correlation between cytotoxic effects of nerve fibres and glial cells could be established with acute or chronic animal toxicity, atomic weight or Periodic classification. The effects of metallic ions in vitro do not demonstrate nerve cell specificity as seen in vivo and a variety of mechanisms may be implicated in the cytotoxic action.”

“The pathogenesis of drug-induced autoimmune antibodies is in most cases uncertain. The recent demonstration of T cell aberrations in human and experimental drug-induced autoimmune disease suggests that immunodysregulation might form the basis of an uncontrolled B cell autoreactivity leading to autoantibody production. In the present study, lymphocytic stimulation by phytohemagglutinin (PHA) and concanavalin A-activated suppressor cell activity was measured in an experimental model of mercury-induced immune complex glomerulopathy associated with anti-nuclear antibodies and vasculitis in PVG/c rats. Both general T cell reactivity to PHA and concanavalin A-activated suppressor function as measured by a syngeneic target cell assay were found to be significantly decreased in mercury-diseased rats as compared with saline-injected control rats. Furthermore, the effect of neonatal and adult thymectomy on the course of the mercury-induced disease was studied. Anti-nuclear antibody activity and glomerular immune aggregate formation were found to be accelerated considerably by neonatal thymectomy, whereas thymectomy at adult age had no significant effect on the interval between the start of mercury administration and the appearance of serological and renal abnormalities. From the results it is concluded that mercury affects both effector and regulatory T cell functions and that immunodysregulation seems to be of pathogenetic significance in this model of drug-induced disease.”

“It was noted that the mercury vapour levels in dental surgeries tended to show a fluctuation throughout the working day. The ambient levels above the threshold limit value of 0·05 mg m-3 only occurred in a few surgeries. What was more important was that high concentrations of mercury vapour were found in certain areas and occurred as the result of certain procedures, sometimes for very short periods. These levels are particularly hazardous if they occur in ‘breathing zones’ which then place the operator and assistant at risk. This does not mean that the ambient levels should be disregarded. Good mercury hygiene is most important and is under the control of the dentist. This begins with the design of the surgery; the materials used for floor and wall coverings; the use of continuous surfaces together with good ventilation and heating. Mercury should not be dispensed within the surgery and if necessary a special preparation area should be used where spillage trays are installed. Hot air sterilisers are another source of high concentration of mercury vapour and should be installed outside the surgery.”

“The expired air of a group of 48 persons, 40 with and eight without dental amalgam restorations, was analyzed for its mercury content before and after chewing. Expired air samples were collected in polyethylene bags, and a known quantity of each was pumped into the mercury detector for measurement. The results showed that examined subjects with dental amalgams had higher pre-chewing mercury levels in their expired air than those without amalgams. After chewing, these levels were increased an average of 15.6-fold in the former and remained unchanged in the latter group. It was concluded that in situ dental amalgams can increase the level of mercury in expired air.”

“The significant aspect of the present study is that chronic exposure to lead, cadmium, or mercury produces immunosuppression to a viral agent.”

Galvanic cells may be created when dentures made of cobalt-chromium alloys are placed on teeth with metallic restorations. The power of such cells was evaluated in an in vitro galvanic using amalgams, gold alloy, and nickel-chromium alloys. The amalgams and one of the nickel-chromium alloys revealed high corrosion currents when placed in contact with cobalt-chromium alloy, the conventional amalgam showing the highest values. The gold alloy and another nickel-chromium alloy exhibited low corrosion currents and they were noble with respect to cobalt-chromium.