Symptoms related to exposure
to mercury from dental amalgam

Dental amalgam has been used for more than hundred years, and is still the most frequently used material for dental restoration. The alloy consists of mercury, silver and tin (50 %, 35 % and 15 %, respectively). In some modern amalgams silver has been partly replaced by copper. It is well known that chronic mercury poisoning may occur from occupational exposure to small amounts of mercury over a long period of time. Neurological or psychiatric symptoms include depression, irritability, exaggerated response to stimuli, excessive shyness, insomnia, emotional instability, forgetfulness and confusion. Other neurological signs includes spasms of the arms, legs or facial muscles, lack of muscle co-ordination and mental retardation. Additional symptoms found are excessive perspiration, uncontrollable blushing, and a fine tremor of the fingers, eyelids, lips and tongue.

One of the controversies regarding dental amalgam is if any mercury is released and taken up by inhalation. However, it has been shown that mercury vapour is released during the insertion, polishing and removal of amalgam. Furthermore, mercury vapour is continuously released from dental amalgam during tooth brushing, chewing and the intake of hot drinks. This mercury can be measured in expired air and saliva. From different studies it can be estimated that mercury from amalgam accounts for a small percentage of our total intake of mercury, and represents less than 10 % of the daily intake of mercury from food and other non-dental sources. It is estimated that the average uptake of mercury from amalgam fillings in Swedish adults is within the range 4 - 19 m g/day. This rather broad range reflects the uncertainty inherent in the model and the data used. This mercury is distributed and taken up by the central nervous system.

Because of the well-known toxicity of mercury and the demonstrated release of mercury from amalgam filling, a controversy now exists, as to whether amalgam fillings are toxic. There are many studies where no significant correlation has been found between amalgam load and subjective symptoms, but there are also studies where such relationships have been reported. Of major concern have been kidney dysfunction, neurotoxicity - classical problems associated in the past with occupational exposure, and speculative involvement in the cause of multiple sclerosis and Alzheimer disease, reduced immune competence resulting in varied disorders, increase in still-birth and birth defects and general health.

Despite several studies there is at yet, no evidence that amalgam fillings can cause any disease, except for allergic reactions to the filling materials. Nor are there any studies to indicate that removing the amalgam leads to better health. The hope of regaining health by removing amalgam fillings is not a new phenomenon. Even as early as 1850 in the USA there were dentists who claimed that removal of amalgam fillings could result in miraculous cures among patients with chronic diseases. However, the general conclusion is that dental amalgam does not constitute any hazards to health in individuals who are not allergic to mercury.

Occupational exposure to elemental mercury in dentistry is a well known phenomenon that has gained considerable recent attention. The primary source of an occupational exposure to practising dentists is inhaled elemental mercury vapour. The varied factors that are thought to contribute to mercury exposure in dentists can be categorised into groups of characteristics: personal, professional practise and office. Personal characteristics include items such as diet, age and non-occupational mercury exposure. Professional characteristics include items such as the number of amalgam fillings carried out per week, techniques used during the operation and how scrap amalgam is stored. Office characteristics include such features as prior accidental mercury spills, flooring material and the number of operations.

Clinical management and treatment

The patients often complain of neuraesthenic symptoms, headache, tiredness, memory disturbances, difficulties in concentration, insomnia, dizziness, and myalgia. Patients with symptoms referable to the mouth should be examined by a dentist. The measurement of mercury in blood or urine is not recommended as a routine procedure. Removal of amalgam fillings is not recommended. There is no specific treatment.