Fluoride is an ion of the element fluorine. It occurs naturally in water, rock, soil, and in living tissue. Fluoride does not occur in its free form, but rather is always bound to another element.
How does fluoride work to prevent cavities?
The answer to that question depends on how the fluoride ion is presented, either systemically or topically.
Systemic fluoride is introduced to the body through sources such as fluoridated water. It has been determined that the optimum concentration of fluoride in drinking water to provide cavity prevention safely is in the range of 0.7 - 1.2 ppm. Most municipalities maintain a concentration within this range, but people relying on natural sources of drinking water should test their water to determine if fluoride supplements should be prescribed. Systemic fluoride begins to exert its effects while teeth are still forming. Bones and teeth have an organic matrix, but they actually gain their strength and hardness from an inorganic, crystalline composition known as hydroxyapatite. Cells responsible for tooth and bone formation utilize available calcium and other minerals to form the hydroxyapatite matrix. When fluoride ions are also available, such as occurs when fluoride is ingested, cells will use them to produce an additional compound called fluorapatite. Fluorapatite becomes integrated in the inorganic matrix, resulting in a more durable and acid-resistant substance. This has been shown to have a beneficial effect in reducing the incidence of dental decay.
Although the benefits of systemic fluoride have been well documented, we are now learning that the topical effects of fluoride ions may even be more important. Topically applied fluoride ions can be applied to the teeth through toothpastes, over-the-counter fluoride rinses, and dentist-applied fluoride varnishes or foams. The topically applied fluoride exerts it's effects in several ways. First, it is known to inhibit the ability of bacteria to produce plaque on the teeth by blocking the function of important bacterial enzymes. Secondly, topically introduced fluoride ions lead to reduced demineralization and increased remineralization of tooth structures. Acids from bacterial toxins act by causing loss of calcium and other minerals from the tooth surface. This is the beginning of the decay process. Fluoride acts to slow the process of demineralization and promote remineralization thereby preventing the onset of the carious lesion. It has been shown that the topical effects of systemic fluoride ions which end up in saliva may actually be more important than the effects during tooth formation.
What we need to learn from this discussion is that, to optimally fight cavities, we need to make sure we are providing our families with a fluoridated drinking water source, as well as supplementing that with the use of an ADA accepted fluoridated toothpaste. As an adjuct, all children under the age of 18 should have a topical fluoride varnish application by the dentist every 6 months. If we apply the beneficial effects of fluoride, along with excellent oral hygiene and regular dental visits, we can win the war against tooth decay.