The human mouth is a busy place, what with words being formed and projected as speech, food and drink arriving at all hours, and air passing to and from the lungs. But we don’t normally think of the oral cavity – to use medical parlance – as the site of interactions that can affect our overall bodily health.

In fact, the mouth is the locus of reactions between nutrients and a number of different physiologic systems that can have far-reaching consequences for bodily functions as basic as cell replication and repair and the response of the immune system.

These are complex reactions, not matters that we’re likely to go around thinking about every day. A balanced diet with adequate zinc, selenium, strontium (for bones and teeth), vitamins D and B6 will normally keep them in good order. But, something we do have to pay attention to are dental caries, or cavities, as most of us call them.

Dental caries are caused by bacterial infection, which is strongly aided and abetted by what we eat, particularly sugar. Although the incidence of caries is down, more than half of North American children still have them, largely because 50% of their caloric intake comes from refined sugars and saturated fats.

The incidence of caries has fallen largely because of the widespread use of fluoride in developed countries over the past 40 years. Fluoride works, no question, but dosage is critical. A daily intake of more than two parts per million may cause motor dysfunction, IQ deficits and learning disabilities, especially in children.

The risks and benefits of fluoride have long been controversial. Much more clear-cut are the dangers posed by mercury in amalgam fillings, an alloy of silver, copper, tin, zinc and at least 50% mercury.

Mercury is unstable. Apply even a little heat to a drop of the metal and it will evaporate. In an amalgam filling, the friction of chewing causes mercury to vapourize for about 90 minutes thereafter, spreading throughout the body.

Mercury is also extremely toxic. It is associated with at least 30 damaging cognitive, behavioral and developmental conditions, plus a long list of diseases to which it is known to be a contributing factor. And it is cumulative, collecting in the brain, adrenal and pituitary glands and elsewhere in the body.

So why, one might ask, is mercury amalgam still used for 75-80% of the fillings in North America? There are alternatives, after all: gold, ceramics and composite, a mixture of powdered glass or quartz in resin.

The simple answer is that amalgam is cheap, durable and easy to work with. But the full answer is much more complicated. Mercury in fillings has been a hotly debated issue for more than 150 years. Literally thousands of studies have been done, review panels created and, latterly, law suits launched, mostly against governments on the grounds that they didn’t act to protect the public. Now, mercury poisoning even has its own name: Dental Amalgam Mercury Syndrome (DAMS.)

While both the American and Canadian Dental Associations still insist that amalgam is safe, a growing number of dental offices prominently display a sign that says: This is a Mercury-free Dental Clinic. Or words to that effect.

So who are you to believe? As always, let caution be your guide; if dentists are putting up signs, you can be sure there is cause for concern. Where there’s smoke, as the saying has it, there’s usually fire.

©Dr. Ashely Gordon, 2006.