Mercury–a factor in mental disease? Part 1. Can mercury-silver amalgams cause psychiatric symptoms?
Historically, hatters in England who used mercury in the felt hat industry got the shakes and became unstable – thus the term “Mad as Hatter.”
Mercury dissolution from dental amalgam into saliva.
The safety of dental amalgam use in patients needing dental fillings is well established, based on the relatively rapid decline in urinary mercury concentration following filling. Only a small number of studies, however, have attempted to describe the method of transfer of the mercury in the amalgam to the saliva. Atomic absorption spectrophotometry was utilized to study reduction and vaporization and showed excellent sensitivity in quantification. Using this method, the release of mercury from the amalgam to the saliva was studied. To begin with, in experiments in vitro, the release of mercury from the test amalgam to fresh saliva was shown to be approximately 10 times as great as the amount released to an inorganic test solution. The mercury concentration in the mixed sa liva sample obtained from 198 test subjects under ordinary conditions was then measured. The concentration of mercury in the mixed saliva obtained from 65 test subjects with either amalgam-filled teeth nor exposure to exogenous mercury was 1.48± 1.73 ppb using the a rithma tic mean, and 0.88?; 2.71 ppb using the geometric mean. These values were felt to represent the normal mercury concentration in mixed saliva. In test subj ects with amalgam-filled teeth, on the other hand, a significant correlation was noted between the mercury concentration in the mixed saliva and the number of teeth filled with amalgam, with a correlation coefficient of y=0.44. Measurement of the release of mercury from an amalgam·filled tooth to the saliva gave a mean of 12.3 ng/ml per filled tooth in the molar region as measured immediately after filling. Since the mercury concentration in the saliva showed a rapid decrease within 24 hours, it is not likely that this amount of mercury is ingested continuously. Test subjects with amalgam-filled teeth thus ingest an amount of mercury larger by approximately 2.1 p.g than those without such fillings, through the swallowing of saliva. Since this amount of mercury corresponds to less than 1/ 10 the amount contained in the food of a normal daily diet, the safety of the amalgam-filling of the teeth is thought to be confirmed.
Electrochemical potentials of amalgam restorations in vivo.
The potentials of 407 amalgam restorations have been determined in vivo. The measurements were performed with very high impedance equipment, and relative to a Ag/AgCl reference electrode. The readings varied from -23 mV to -595 mV, with 90% of the readings confined to within -127 mV to -431 mV and a mean value of -226.1 mV. Of the restorations, 394 were measured twice, and no significant difference could be found between the first and the second reading. During the study, eight new restorations were inserted. Their potentials varied from -180 mV to -565 mV, with a mean of -339.4 mV, which was significantly lower than that of the older restorations.
An oral and psychosocial examination of patients with presumed oral galvanism
The present investigation was performed to elucidate possible etiological factors behind the complaints reported by 62 patients referred because of presumed oral galvanism. Twenty-nine patients, matched with a subsample of the test group regarding age and sex, comprised a control group. The patients were examined regarding oral medical and stomatognathic health. Their psychological and social health and symptoms were evaluated by means of a standardised interview and 5 self-rating questionnaires. A complex symptomatology including symptoms from both the oral regions and other parts of the body constituated the most distinctive feature of the patients in the test group. The clinical examination as well as patient-perceived symptoms revealed high prevalences of parafunction and dysfunction in the muscles of the stomatognathic system. Furthermore, general complaints were mainly related to muscles of the extremities, and diseases of the joints and muscles were the most commonly reported disorder. The findings at the oral medical examination revealed no differences between the groups, except for signs of parafunction. Patients in the test group gave evidence of being more exposed to negative social events and the results clearly indicate a psychogenic component behind the reported complaints.
Effect of dental amalgam restorations on the mercury content of nerve tissues.
In an autopsy study in two men and an experimental study performed on three female beagles the mercury burden of nerve tissues was determined. Nerve tissues from the head and face region and from three peripheral nerves were analyzed for mercury content with the aid of atomic absorption spectroscopy. In the dogs dental amalgam restorations were placed so as to investigate the possible influence from the amalgam on the mercury content of the tissues under study. The mercury content in man and dogs differed widely from one nerve to another, with no apparent relation to the number, type, or location of tooth restorations.
Galvanic currents between dental alloys in vitro
The galvanic current densities between gold, amalgam and cobalt-chromium, three different classes of dental alloys, were determined in vitro in artificial saliva kept at 35 degrees C. The maximum current density of 200 microA/dm2 was obtained between the conventional amalgam and a type III gold alloy. Galvanic currents of lesser magnitude could also be measured between amalgams high in copper and the other alloys. No measurable current densities were obtained between gold alloys and between gold and cobalt-chromium alloy with the exception of a casting and a solder gold alloy commonly used in combination.
Mercury vapour released during the removal of old amalgam restorations.
These values surprised us, as we had assisted in some observations, made by a Specialist Inspector of Health and Safety Executive, of mercury levels in the breathing zone of dentists following a number of procedures, including the removal of amalgam with high speed drills. These unpublished observations indicate that high levels of mercury vapour can be released during the cutting of cavities in teeth previously filled with amalgam, when minimal aspiration and cooling water are used. This paper describes some experiments performed to clarify the position and if possible measure and qunatify any exposure to mercury vapour during the preparation and restoration of cavities.
Effects of fluoride on screech owl reproduction: teratological evaluation, growth, and blood chemistry in hatchlings.
The effects on reproduction in screech owls (Otus asio) of chronic dietary sodium fluoride administration at 0, 40, and 200 ppm were examined. Fluoride at 40 ppm resulted in a significantly smaller egg volume, while 200 ppm also resulted in lower egg weights and lengths. Day-one hatchlings in the 200 ppm group weighed almost 10% less than controls and had shorter crown-rump lengths. No gross abnormalities were apparent. Skeletal clearing and staining revealed significantly shorter tibiotarsus lengths in the 40 ppm and 200 ppm groups and a shorter radius-ulna length in the 200 ppm group. By 7 days of age, body weights and lengths did not differ from controls, but the tibiotarsus in the 200 ppm group remained shorter. No significant differences were detected in hematocrit, hemoglobin, plasma calcium or alkaline phosphatase. Plasma phosphorus levels were higher in the 40 ppm group than in controls. These results, in combination with the findings of Pattee et al. [25], revealed significant impairment of overall reproduction, suggesting that sodium fluoride could cause slight to moderate reproduction disorders in owls in fluoride-polluted areas.
A model for recording mercury release from an amalgam surface.
The release rate of mercury from a conventional, a dispersed phase or a spherical high copper content amalgam under static conditions in stimulated or artificial saliva has been measured and found to decrease approximately exponentially with time. A higher initial release rate was observed for mercury in stimulated saliva than in artificial saliva during the in vitro experiments. In a pilot study corrosion current was recorded from an amalgam specimen immersed in saliva, and was found to decrease approximately exponentially with time. After brushing the surface of the amalgam during two subsequent periods, in a manner similar to toothbrushing, an increase in corrosion current was measured indicating the removal of loosely bound corrosion products. A model describing the periodical mercury release from an amalgam surface has been proposed.
Quantization of nickel and beryllium leakage from base metal casting alloys.
Fourteen dental casting alloys were analyzed for release of nickel and beryllium into acidic salivary solutions in vitro. Corrosion rates of varying pH levels and time in solution were calculated through the 120-day level, and the possible significance of these rates to allergic reactions or other health hazards were postulated.