The mercury amalgam filling, which is approximately 50 percent mercury, has been in use for over 150 years. Dentists have continued to use it because it works. It has proved itself capable of withstanding years of use, even in the back teeth where the heavy duty chewing takes place.

Until about 10 years ago, scientists believed that mercury vapour was only released during the day or so that it takes the average filling to fully harden. But in 1979, researchers at the University of Iowa found that small quantifies of mercury vapour were released from older fillings during chewing. This is where the “anti-amalgam” dentists enter the scene.

The theory is that this mercury vapour is poisoning patients, resulting in a range of symptoms including insomnia, epilepsy, leukemia, Hodgkin’s disease, arthritis, mononucleosis, PMS and multiple sclerosis. The implication is, that the various national dental boards and associations are either unaware of the problem or unwilling to admit the treatment that they have been administering for all of these years has been poisoning their patients.

The effects of mercury poisoning are well known. The inhalation of mercury vapour or ingestion of mercury compounds results in damage to the nervous system and brain. The classic example occurred in the 19th century, when hat makers used mercuric nitrate to help shape the felt. They absorbed the mercury through theirs kin and inhaled the vapour. The results were uncontrolled tremors, difficulty walking and finally insanity. They literally became as mad as hatters.

The anti-amalgamists advocate removing all mercury fillings and replacing them with a newer plastic composite material.

Besides being an expensive procedure, the composite fillings rarely last more than three years whereas the mercury fillings can be expected to last five to 10 years or longer. Composites are also more expensive to replace and less resistant to recurrent decay.

In North America over 100 million people have mercury amalgam fillings, but until 1979 less than 50 cases of mercury allergy had been reported. By all measures the treatment was considered safe.

Countering this historical evidence, the majority of the anti-amalgamist evidence appears to be anecdotal. Typically, a patient with symptoms that have not responded to any other form of medical treatment, has all of fillings replaced and within hours or days the symptoms are gone. A cure for the anti amalgamists, but no accurate records, no follow up, no long-term studies.

Measuring the mercury vapour content of the air trapped in a patient’s mouth during chewing, they have discovered levels approaching the legal limit for air quality in the workplace—a disturbing prospect until you realize that during the chewing process only a small quantity of air is trapped in the mouth. The actual quantity of mercury released is therefore minute, compared to that breathed in by a worker during an eight-hour work day, which is what is used to set the air quality limit. When the chewing is finished, the air in the mouth is replaced and quickly returns to near-zero levels of mercury vapour.

But the real test of this question would be the measurement of the blood mercury level. If mercury fillings were really poisoning people, we should be able to detect high levels in the general population. With the exception of those who regularly work with mercury, repeated tests have shown that the general population has blood mercury levels well below the level at which adverse health effects have been noted.

No correlation has been found between the number of amalgam fillings and blood mercury levels, neither have the anti-amalgarnists demonstrated any link. They have never measured and published the blood levels of the patients that were so miraculously cured, and which could have helped to prove their case.

If anyone could be expected to be found suffering from mercury poisoning, it should be the dentist. In addition to any fillings of his or her own, the dentist must handle between two and three pounds of amalgam per year and inhale the vapour and debris of several thousand removed fillings.

Surveys have shown that as many as 10 percent of dental surgeries have mercury vapour levels at or above the legal workplace limit of 50 micrograrns/cubic metre. Despite all of this mercury, dental personnel are not being poisoned. Blood and urine levels maybe up to four times higher than those of the general population, but they are still well below the accepted limits.

The techniques of some of the leading anti-amalgamists are reminiscent of other bogus health practitioners. In 1983, a Dr. Huggins reported that he had cured 80 percent of the 150 multiple sclerosis patients that he had treated, prompting the National Multiple Sclerosis Society in the US to issue a statement warning that “this therapeutic claim … involves economic implications, in terms of expense to the patient and great profit to the dentist.”

In 1989 the American Dental Association Council on Ethics concluded that any dentist who represents dental treatment as a cure for disease, infection or other condition, without the support of accepted scientific knowledge or research, is acting unethically.

It is a pity that even when it comes to health care, it is still a matter of “Buyer Beware”.