Mercury in dental fillings (search) does not cause Alzheimer’s disease, multiple sclerosis or other health problems, according to a new review of all current research.

But will this put to rest the concerns many people have?

It’s a sensitive issue. Methyl mercury (search) is the type found in fish, and has been found harmful to the brain in large amounts. The EPA advises women to avoid eating mercury-rich fish during pregnancy for that reason.

However, mercury in dental fillings is a different type of chemical compound — an amalgam or blend of copper, silver, and mercury. Dentists have used this blended metal for more than 150 years. But over the years, concerns about mercury fillings have been raised, writes Meryl Karol, PhD, an epidemiologist with the University of Pittsburgh School of Public Health.

Karol chaired the expert panel whose research review was released today. Scientists from the National Institutes of Health’s National Institute of Dental and Craniofacial Research, the Center for Devices and Radiological Health of the FDA, the CDC, and the Public Health Service’s chief dental officer, were among those experts.

The Evidence

Only 300 studies published since 1996 had sufficient merit to be included in their report — studies that analyzed mercury in urine samples as a marker for mercury exposure. Methyl mercury from fish is not found in urine samples, explains Karol.

Large population studies, animal toxicity studies, and studies of effects from various levels of mercury exposure were included. Researchers also looked at whether it was biologically possible for mercury vapor from fillings to cause brain disorders and other health problems, she notes.

The panel’s conclusion: “Current research is insufficient to attribute various complaints to mercury in dental amalgam,” writes Karol. Even those people with allergic reaction to dental amalgam “did not have high levels in their blood,” she adds.

Also among the panel’s conclusions:

—The evidence showed that mercury vapor is released from dental work and absorbed in the body. However, about 95 percent of people in the studies had mercury levels at or lower than the level deemed harmful by the WHO.

—The long-term use of nicotine chewing gum (over two years) combined with intense chewing and more than 20 dental amalgam surfaces presents the greatest chance that urine mercury measurements exceed the general population and approach a level seen in people who have occupational exposure to mercury. However, the reports state that adverse health effects for long-term nicotine gum chewers was not evaluated.

—Bruxism (grinding teeth) and dental amalgam placement and removal appear to have less impact on exposure than the use of nicotine chewing gum.

—Allergic sensitivity to dental amalgam seems to affect a small percentage of people.

—Insufficient research has been done to support or refute whether dental amalgam causes antibiotic resistance in the human gut or that it may cause any autoimmune disease including multiple sclerosis.

—Three studies also failed to support a role of dental amalgam as a factor in the development of Parkinson’s disease or Alzheimer’s disease.

—Human studies have failed to support or refute a link between dental amalgam with brain damage in a developing fetus.

—Both methyl mercury from fish and mercury from dental amalgam have been found in breast milk. Rat studies show that high exposure of mercury vapor among pregnant rats and monkeys induces behavioral abnormalities — but no studies have looked at whether low-level exposures affect brain development.

Although some people undergo chelation therapy to treat their symptoms, animal studies have shown that chelation therapy works to bind and remove mercury from the kidneys, but not from the brain, Karol notes. However, chelation carries a host of problems — possible adverse health problems including headaches, dizziness, nausea, and the loss of essential metals.

Chemicals used in chelation therapy have been harmful to the developing fetus, she adds.

Why Mercury Fillings Are Safe

Mercury amalgam fillings “are 100 percent safe,” says Cynthia Trajtenberg, DDS, professor of restorative dentistry and dental biomaterials specialist at the University of Texas Dental Branch at Houston. She was not involved in today’s report, but offered her insights.

The safety “all depends on how molecules are combined,” she tells WebMD. “Salt is sodium chloride, but if you put pure chloride on your steak you will die. If chloride is combined with sodium, it’s safe; it’s even a nutritional element. It’s the same with mercury. Mercury in dental fillings is combined with silver and copper, and is transformed into a stable metal material that is not easily released into the oral cavity. Therefore, it is not harmful.”

One study showed that it would take 300 tooth restorations to create mercury toxicity — “but that’s impossible because we only have 32 teeth,” she tells WebMD. “Eating salmon and deep sea fish more than twice a week gives more mercury than a single amalgam.”

Several medical societies including the American Dental Association, the Alzheimer’s Association, the American Academy of Pediatrics, and the Multiple Sclerosis Society all agree there is no proven link between silver or amalgam fillings and mercury toxicity that can cause neurological disease, Trajtenberg adds.

“There’s a lot of misunderstanding in the medical community about this,” she adds. “I get a lot of patients requesting total replacement of fillings because their doctor said they were harmful. It creates a lot of anxiety among patients, but it is not evidence-based. In Germany, there have been cases of metal reactions to fillings. But not usually to amalgam fillings — it’s with gold.”

It’s true that medical symptoms — like headaches, tremors, mood swings — may lead people to suspect mercury toxicity, she says. “But it’s not related to small doses from dental restorations. We always want physicians to do further tests with their patients to look for neurological or psychiatric disorders that may cause similar symptoms.”

The report was funded by the U.S. Department of Health and Human Services, and coordinated by The Life Sciences Research Office, Inc., a nonprofit, independent research group in Bethesda, Md.

By Jeanie Lerche Davis, reviewed by Brunilda Nazario, MD

SOURCES: “The Potential Health Effects of Dental Amalgam,” September 2004. Cynthia Trajtenberg, DDS, professor of restorative dentistry and dental biomaterials specialist, University of Texas Dental Branch at Houston. Agency for Toxic Substances and Disease Registry.