Mercury

“Particles of a conventional lathe-cut, a spherical non-gamma 2 and a copper amalgam have been gastrointestinally administered to rats for the purpose of evaluation of the dissolution resistance. The animals were sacrificed after 20 hrs. The contents of copper, cadmium, indium, mercury and zinc in kidney, liver, lung or blood were measured using nuclear tracer techniques. From a copper amalgam an extreme release of copper was demonstrated. This study stimulates the clinical condition of elemental release from swallowed amalgam particles after amalgam insertion or after removal of old amalgam fillings. Specimens of the same types of amalgams were also exposed to artificial saliva for a period of 10 days. The amounts of copper and mercury released were measured with flame and flameless atomic absorption spectrophotometry respectively. The levels of copper and mercury released from the copper amalgam were approximately 50 times those of the two other amalgam types studied.”

“A 54-year-old man had a syndrome resembling amyotrophic lateral sclerosis after a brief but intense exposure to elemental mercury. The syndrome resolved as his urinary mercury levels fell. Mercury toxicity must be considered not only in individuals with recent anterior horn-cell dysfunction but also with otherwise unexplained peripheral neuropathy, tremor, ataxia, and a gamut of psychiatric symptoms including confusion and depression.”

“There is adequate evidence that dental amalgam restorations, during and after placement, results in the release of Hg into the patient’s body. Whether the Hg released from amalgam is due to placement procedures, surface abrasion, or later corrosion breakdown, there is evidence that a low level Hg release continues for years. It is generally agreed that if amalgam was introduced today as a restorative material, they would never pass F.D.A. approval. With new and more accurate techniques of measuring Hg levels, especially in tissue and blood, additional studies are necessary to relate blood-Hg levels with dental amalgam restorations. Studies must relate existing restorations as well as the placement of new restorations to body-Hg levels. It is possible that we have accepted a potentially dangerous material as being safe.”

Sixty-eight consecutive patients (9 males, 59 females) referred for symptoms alleged to be caused by oral galvanism were investigated according to a standardized examination program including clinical examination, epicutaneous patch test with dental materials, haematologic screening, salivary test, calculation of currents created at metallic contacts between restorative materials and testing of electrical taste thresholds. No clinical entity could be identified but recognized clinical conditions that could possibly explain the complaints for which the patients were referred were prevalent. The most common symptoms reported were a smarting sensation in the mouth (71%) and different distant symptoms (47%). As regards oral signs, some of them showed similar prevalences as have been found in a general Swedish population. The main exception was changes at the apex of the tongue – found in 15%. Allergic skin reactions to dental materials were found among 25% of the patients. Mean values of blood and saliva parameters did not differ from what is considered normal. The distribution of currents created by contacting dental metallic restorations showed no deviation from the corresponding currents calculated in a control group. The median value for lowest electrical taste threshold in the group of referred patients was significantly lower than in a control group.

RESULTS Mean mercury levels recorded during the amalgam removal procedure are shown in Fig. 1. Higher vapor levels were obtained with dry cutting than with wet cutting at each distance. Levels for dry cutting remained similar at all distances measured within 24 inches. Samples that were cut wet showed a general decrease in vapor levels as distance increased, although levels at 6 and 12 inches were similar and levels at 24 and 36 inches were equal. Sample means were compared statistically using a Student t-test.

Patient exposure to mercury from dental amalgam and restorative procedures has not been studied as extensively as mercury exposure to dental personnel. One. study found that in a group of 114 adults not undergoing dental treatment, only six had measurable mercury in the urine, and one of those persons was using a mercurial diuretic.’This was compared to a group of 24 persons currently undergoing dental treatment. Of that group five showed mercury in the urine before and after treatment.

“The methods of the quality control of medical biological preparations, including tests on animals, do not ensure the complete absence of toxicity in a final product. The use of the method of ‘subcultures with the introduced preparation’ makes it possible to determine the toxicity of both specific and nonspecific components of vaccines and sera from the number of dead and damaged cells. The toxic action of preparations kills and damages the cells at the site of injection, thus inducing the formation of autoantigens whose effect on the body cannot be predicted. Thus thimerosal, commonly used as preservative, has been found not only to render its primary toxic effect, but also capable of changing the properties of cells. This fact suggests that the use of thimerosal for the preservation of medical biological preparations, especially those intended for children, is inadmissible.”

“Yet the kidneys receive one fourth of the circulating blood supply and have the ability to accumulate circulating substances to concentrations far exceeding those found elsewhere in the body.
This propensity to accumulate metals and other toxicants contributes to the unusual sensitivity of the kidneys to toxic agents. The high concentrations of nephrotoxins achieved within the kidneys also provide an opportunity for their detection by nuclear analytic techniques both in vivo and in vitro.”

“Amalgam has, ever since its introduction 150 years ago, been the subject of recurrent controversies because of its mercury content. Amalgam is an unstable alloy and continuously gives off mercury (Hg) in the form of gas, ions and abraded particles (Stock, 1939 a, Radics et al., 1970, Mocke, 1971, Till and Wagner, 1973, Svare et al., 1981). Amalgam contains an especially cor-rodible gamma-2-phase of tin and mercury. There is also a small phase of fluid mercury with dissolved tin (Brecht-Bergen, 1933). Tin dissolves continuously in surrounding fluids and also forms weakly soluble but not insoluble compounds which are easily abraded in vivo. When tin (also zinc and copper if present) dissolves, mercury is set free  and will evaporate and ionize. The Hg vapor pressure over silver amalgam amounts to 10-25  percent of that over pure mercury; at a Hg  content of 54 percent in the amalgam the vapor  pressure is 25 percent (Brecht-Bergen, 1933).  The actual rate of evaporation depends on the  air movement over the fillings (Stock, 1939 a).”

“Slow, retrograde seepage of ionic mercury from root canal or Class V amalgam fillings inserted many years previously, recurrent caries and corrosion around filling edges, and the oxidizing effect of the purulent response may lead to multiple sclerosis in middle age. Epidemiologic studies of MS consistently reveal more neurological disease in the north, inferentially because there may be less caries and therefore fewer fillings done in the south. Clinical and epidemiologic data also suggest that a second heavy metal, lead, may operate almost interchangeably with mercury. Possibly, cases of unilateral MS derive from mercury-amalgam fillings in ipsolateral teeth, whereas the generalized disease may result from ingestion or inhalation of volatile mercury or exhaust fumes of lead additives to gasoline. The forensic and preventive-medical challenge is to identify, monitor, and resolve questions of hidden heavy metal hazards in a high technology society, especially those of lead and mercury. Further clinical-epidemiologic and basic science studies of heavy metal assays in whole blood, CNS tissues, packed cells, and serum are warranted. Prevention awaits further testing of the hypothesis and experience with substitute filling materials.”