Something New About Fluoride in the Water

Something New About Fluoride in the Water

Since I first wrote about fluoride in the water about twelve years ago, there have been some significant changes in the science. In some areas, fluoride is naturally occurring. In fact, in many parts of the country, fluoride occurs naturally in well water. Early in the 20th century, scientists discovered that fluoride in the water during the formative years for the enamel (hard outer covering) of the teeth greatly reduces the incidence of tooth decay throughout the life of the affected person. This effect continues even after the person has left the fluoridated area as long as the person ingested the fluoride consistently during the first 9 or so years of life. What I have said so far is a substantiated scientific fact. But just as in most things, it’s not as simple as it looks on the surface. While it is known that fluoride that is ingested during the formative years for tooth enamel (up to about 9 years old) reduces tooth decay, too much ingested fluoride over a sustained period causes permanent unsightly dark spots on the teeth. Fluoride was first added artificially into municipal water supplies in a controlled fashion in 1946 in a town in Michigan. Up until just a few years ago, it was thought that 1 part fluoride per million parts water would cause about a 35% reduction in tooth decay for the duration of the affected person’s life. This level of fluoride also had a low incidence of discoloration of forming teeth (called fluorosis). What has been learned recently is that at the rate of one part per million, the decay prevention effect is much lower than was previously thought. In order to get a really significant decay reduction from ingesting fluoride, much higher levels of fluoride would be needed in the water. This poses a problem because a higher level of fluoride in the water also causes a higher level of discoloration.

There is a positive side to all of this. The same study that informed all of us in the field that what was considered optimal fluoride level in the water (one part per million) has much less effect than was previously thought, also noted that fluoride applied directly to the teeth at high level like fluoride in the toothpaste is actually much more effective than previously thought. To summarize, fluoride in the water has a lot less effect than previously thought, but fluoride in the toothpaste has much more effect than was previously thought. Fluoride in toothpaste is a form of topically applied fluoride. It is 1000 times as concentrated as fluoride in the water (1000 parts per million). As well, fluoride varnish applied at the dental office which is more than 20,000 times as concentrated (20,000+ parts per million) as fluoride in the water is also more effective at preventing tooth decay than was previously thought. It is important to note that none of these topically applied fluoride preparations are meant to be ingested (swallowed). They are in effect, applied to the teeth for a couple of minutes and spit out, or in the case of fluoride varnish, applied to the teeth and left in place for a couple of days.

The scientists who disseminated this information to the world are located at the Centers for Disease Control in Atlanta, Georgia. The information was released in 2005. This institution is arguably the preeminent source for scientific knowledge concerning health in the world. Don’t let this new information shake your confidence in science. This is the nature of science. It is common in science for there to be three steps forward and two steps back. It is not like a ratchet. It moves in both directions. Science is trial and observation. Sometimes it is found that previous observations had not been scrutinized enough. Sometimes new knowledge comes to light that makes the previous observations not complete or not as relevant as they once were.

So now what do we do with our fluoride in the water? It still works, just not as effectively as we had previously thought. We can’t increase the level because permanent discoloration of the teeth will result in our children. I am sure that in the coming years, it will be up to the voters in each town whether they are going to keep fluoride or stop its addition to town water supplies. But remember the good news, fluoride in toothpaste and in fluoride varnish at the dental office is more effective than we had ever supposed. It is hard even for dentists and other dental professionals to move away from what we have been taught and we have believed for decades. This new wrinkle in the science of fluoride will take years to sink in—both for the public and for some dental professionals. Just when we thought there was little more to say on the subject, fluoride is again a hot topic in dentistry. If you want to know more about fluoride and prevention of tooth decay, ask your dentist.


This article was written by Dr. Mike Christensen and published in the Daily Miner and News, and Enterprise. Local Kenora News Publicatons (1998-2006)