4. What health effects could be linked to the form of mercury contained in dental amalgams?
- 4.1 How toxic are mercury and other metals used in amalgams?
- 4.2 What are the possible negative effects on health of dental amalgams?
4.1 How toxic are mercury and other metals used in amalgams?
Dental workers are more exposed than the general population
© Marcelo Terraza
The way mercury affects the body is highly dependant on how it enters the body and on its chemical form. People can be exposed to mercury released from amalgams by breathing in mercury vapour or by swallowing either elemental mercury leaching from the fillings or small pieces of amalgam that detach from the filling and that can go on to release mercury inside the gut.
Very little of the elemental mercury that comes into contact with the skin or that is swallowed is absorbed into the blood stream. However, a large part of mercury breathed in as vapours is absorbed in the lungs and distributed to the entire body, reaching all organs. The elemental mercury reacts and attaches itself to proteins within the body and is gradually eliminated, mainly through the urine and faeces, reducing its concentration in the body by half every three months in the absence of any additional exposure. The highest concentration of mercury following exposure is usually found in the kidney.
The exposure to mercury vapours from amalgam fillings is fairly low, 5 to 30 times lower than the limits set for workplace exposure, and many orders of magnitude lower than those that can cause long term health effects. In cases of long-term and regular exposure to mercury vapours, for instance in certain work environments considered poor by present standards, the central nervous system is particularly affected. The neurological symptoms can include increased excitability and tremors in fingers, eyelids and lips, which may progress to long term shaking of hands and feet. In addition it can affect the kidneys and cause inflammation of the gums and production of excessive amounts of saliva with a strong metallic taste. Exposure to extremely high doses of mercury – as experienced by some individuals working under poor conditions – may also produce bronchitis and pneumonia.
Dental amalgam can contain silver, zinc, copper, and tin and exposure to excessive doses of these metals can be harmful. The health effects depend on the metal involved and include skin irritation, nausea, vomiting and diarrhoea. More specifically:
- Silver is widely used in industry and for medicinal purposes, and it is present in our food. At very high concentrations it can cause local irritations and a deposition of silver in tissues, but no other harmful effects are known.
- Copper is an essential micronutrient. Copper deficiencies can for instance cause anaemia but exposure to excessive levels can also lead to anaemia and damage the liver, kidney and the immune system.
- Tin dust and fumes can cause lung problems, and if ingested, inorganic tin can cause nausea, vomiting and diarrhoea. Excessive doses of tin can affect the way the body process other metals like copper, zinc and iron.
- Zinc is also an essential micronutrient, and zinc deficiency can lead to a series of health problems. Ingesting large doses of zinc can lead to digestive problems, and can lead to copper and iron deficiencies.
However, there is no evidence of any adverse health effects caused by the presence of these metals in amalgam fillings, apart from some people having allergic reactions to the individual elements. More...
4.2 What are the possible negative effects on health of dental amalgams?
The main exposure of patients to mercury from amalgam restorations occurs during placement or removal of the fillings. Therefore, it is more harmful to remove amalgam fillings than to leave them in place, unless the filling is damaged or defective, or the individual has an allergic reaction to one of the components of the amalgam.
Metals in close contact with skin and mucous membranes are well-known causes of allergic skin inflammation and mercury is no exception. Among allergic individuals, reactions to mercury or any of the metals in dental amalgam can result in inflammation of the gums, and in red and painful sores and ulcers in the mouth. The inflammation is not always limited to the mouth and can be observed as rashes in the face or other parts of the body. However, these reactions are rare and removing the filling usually resolves the problem.
There have been claims that amalgams might be involved in many diseases and in some neurological and psychological disorders such as Parkinson’s or Alzheimer’s diseases, depression and anxiety. However, for many of the claims, scientific investigations have generally provided either refutation or found no link. No link has been found between dental amalgams and chronic fatigue syndrome, kidney diseases, autism, fertility, birth defects or coronary heart disease. There is no indication that amalgam affects the human immune system, and there is no evidence of a link between mercury and human mental health problems or psychological conditions.
Among dental workers, there does not seem to be a link between exposure to mercury and health. Although the level of mercury in the blood is higher in dentists than in the rest of the population, the general health of dentists is good and their lifespan is greater than that for control groups. However, because of possible effects on reproductive health it is important to monitor the levels of mercury in dental clinics to ensure these are not above permitted levels. As the number of amalgam restorations being placed and removed is decreasing, the need for such measures will decrease over time.
The current use of dental amalgam does not harm human health, other than causing occasional local effects, such as allergic reactions, in some dental patients.
Whatever the material chosen, direct restorations may fail, primarily through new caries between the tooth and the filling (secondary caries), fracture of the restoration or tooth, marginal deficiencies or wear. The rates at which these failures occur are difficult to compare since they will vary with clinical technique and from patient to patient. Also, the materials used are not comparable to each other since there have been changes in characteristics and improvements in quality over time.
Dental amalgam remains an effective, strong, durable and relatively cheap tooth filling material particularly resistant to secondary caries, possibly through anti-bacterial activity. It will outlast alternative materials under many circumstances. More...