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Amalgam Allergy and Mercury Poisoning from Dental Fillings

Amalgam allergy is an extremely rare reaction to the mercury used in the amalgam dental filling, also known as “silver filling”. It is an unusual condition and few cases have ever been reported. Just like in any other allergy, the immune system becomes sensitized to the offending substance (in this case liquid mercury) and mistakes it for a foreign invader. When the immune system attacks the foreign substance the body starts producing the symptoms characteristic of an allergic reaction such as an eczema-like lesion on the soft tissues near the restoration.

What is Amalgam?

Amalgam has been used for more than 150 years to repair teeth damaged by decay. The amalgam itself is a mixture of equal parts of liquid (elemental) mercury and alloy powder, which usually contains silver, tin and copper. Sometimes, small amounts of zinc, palladium or indium also are used in the alloy powder. Mercury is the element capable of binding these metals together in a way that can be used to fill a cavity (a small hole in a tooth caused by tooth decay). The actual substance that most likely causes the rare allergic reaction to amalgam in some people is liquid mercury. However, some people may also have an allergic reaction to other components of amalgam such as copper, silver or tin.

Why Is Amalgam Used?

Dentists have long preferred working with amalgam because of its relatively low sensitivity to moisture, such as saliva. This means dentists do not need to be quite as precise when placing amalgam because it is more durable and forgiving than other materials used in tooth repair. Amalgam is also less expensive than any other dental filling material and can withstand substantial chewing stress. However, the use of amalgam in dental fillings has been declining during the past few decades due to a number of different factors, including increased availability of more cosmetically appealing alternative materials.

Risk Factors for Amalgam Allergy

Although this condition is very rare, people with personal history or family history of allergies to metals, especially heavy metals, are more likely to be allergic to amalgam.

Treatment of Amalgam Allergy

In most cases, no medical attention is required to treat an allergic reaction to amalgam. Symptoms usually resolve on their own within a few days. In rare cases, amalgam fillings may need to be replaced with a different restorative material, such as tooth-colored composite resin, porcelain or gold.

Other Potential Risks Associated with Mercury

Concerns about the safety of amalgam are not limited to allergies. For decades, a debate has raged in the dental community over whether or not the mercury contained in amalgam can have toxic effects on the body. Many opponents of amalgam have blamed the substance for a variety of health problems including nerve damage, autism, chronic fatigue syndrome, kidney problems, multiple sclerosis, Alzheimer’s disease, birth defects, compromised immunity, etc. Most experts and public health authorities, including the U.S. Food and Drug Administration maintain, though, that amalgam is safe for use in adults and children over six years of age and there is no link between the use of dental amalgam and the aforementioned health problems.

Mercury is bioaccumulative, which means it accumulates in the body’s organs and tissues over time. This applies to elemental mercury from amalgam as well as organic mercury called methylmercury found in seawater fish and shellfish and inorganic mercury salts that may be present in drinking water. Elemental mercury is absorbed through the lungs by inhaling mercury vapour released from amalgam dental fillings whereas methylmercury and inorganic mercury get in the body through the digestive tract. All forms of mercury accumulate in the kidneys and the brain but their levels of tolerance and potential adverse effects are different. Research shows that people absorb larger amounts of mercury from foods, water and air than from amalgam fillings.

The common symptoms of chronic exposure to elemental mercury are irritability, increased excitability (erethism), excessive shyness, insomnia, muscle twitching and tremors whereas those of chronic exposure to methylmercury include a sensation of pricking on the skin called paresthesia, malaise, speech difficulties, muscle weakness, blurred vision and constriction of the visual field. Chronic exposure to inorganic mercury usually causes inflammation and skin rashes (if mercury comes in contact with the skin) as well as mood swings, memory loss and bloody diarrhea if ingested. However, after evaluating existing studies, the U.S. Food and Drug Administration has found no sound scientific evidence indicating that miniscule amounts of mercury vapour released from amalgam fillings could cause any such effects.

Should I have Amalgam Fillings Replaced?

Low levels of mercury exposure from amalgam dental fillings do not seem to cause any health problems in adults and children over 6 years of age. Since the dangers of amalgam cannot be completely ruled out, it may be recommended that pregnant women avoid amalgam fillings. However, replacing sound amalgam dental fillings is not necessary. Keep in mind that removing these fillings may result in increased release of mercury vapour and its inhalation. But, speak to your dentist if you are allergic to mercury or any other metallic component of amalgam.

Also, read what the FDA has to say about amalgam fillings.