A new patient told me that her son recently had a “silver” filling placed by another dentist without any discussion with her about it. I was discouraged to hear this. As a dentist who abandoned the use of these mercury-containing fillings 15 years ago, I realized that I, and all of us, exist within our own little bubble. My little bubble is a silver-filling-free world. The experience motivated me to write this article. I feel that the issue is simple. I’ll lay out a few facts and, hopefully, enable you to make an informed decision.
Silver fillings should actually be called mercury fillings if the largest ingredient is mentioned first. These fillings are made up of 50 to 52% mercury, 35% silver, and 15% tin. Some brands contain a small amount of copper as well. I was not even aware that my own fillings contained mercury until I was in dental school. There I was taught that, when mixed together, these components hardened into a permanent mass. As I began reading, however, I learned that mercury is released from these fillings every time we chew or brush. Much of this early research was done by a Canadian, Dr. Murray Vimy, in Calgary. In one of his studies he placed mercury fillings in sheep and measured mercury which had crossed the placenta into the lambs born to those sheep. Another study, by F. L. Lorscheider, showed that brain mercury levels in human autopsy studies was directly correlated to the number of amalgam fillings the individual had in their mouths. These studies convinced me that an alternative was essential. I soon abandoned amalgam and began placing composite (tooth colored fillings). There were some problems with early composites, but most of these problems have been eliminated.
Mercury is a toxic element. It occurs as plain mercury or combined with other compounds. Methyl mercury, for example, is very toxic compound; it was responsible for the tainted fish poisonings in Minamata Bay, Japan. Early evidence of mercury toxicity was found in the hatting industry in Britain, where mercury salts were used in the felting of wool. The contamination of workers lead to “Mad Hatter’s Disease”.
We become exposed to mercury from dental fillings by breathing in small amounts of mercury vapor that comes off these fillings as we chew or grind our teeth. When we breathe in this mercury it enters the blood stream through the lungs. Once in circulation it accumulates in the kidneys and in the brain. Once inside cells, mercury binds to different cell structures and kills or affects their function. All forms of mercury cross the placenta to the fetus. In toxicology we discuss the half-life of drugs or compounds. The half life is the time it takes for the body to reduce a compound by one half. Our bodies do this by excreting the substance or chemically neutralizing it. The half-life for mercury vapor in humans is 35 to 90 days. (Tylenol, a common pain-killer, for example, has a half-life of about 2 hours in adults.) You can see that if you are taking mercury into your body every day it will accumulate and never be eliminated.
Studies of what mercury from dental fillings is doing to us come to varying conclusions. However, the Canadian Federal Government in a recent bulletin recommended that a mercury-separating device be installed in the drain lines of each dental office so that, when drilled out of your mouth, mercury does not end up in the sewer lines. Dental mercury, incidentally, is the largest source of environmental mercury contamination in the sewer systems of North America. These devices will become compulsory soon. The government also has specific recommendations for disposing of any mercury-containing waste; it is considered a hazardous toxic waste! Would you want such a material in your mouth? In the same bulletin the Federal Government recommends that dentists “stay abreast of new restorative materials”. I think that means to learn to use alternative materials. Don’t you?
Dr. Larry Hill practices in downtown Nanaimo with his partner, Dr. San Mahara. He traveled to Nepal as a volunteer dentist in September 2008.