Fluoride in the Body and its Role in Enamel Development

Video 2. Enamel Maturation - How is fluoride incorporated into the inorganic phase of enamel, pre- and post-eruptive?
Fluoride is incorporated into the inorganic part of enamel, the inorganic phase, by substitution for either hydroxyl ions or carbonate ions within the apatite lattice. In order for that to occur, in an already maturated or developed apatite crystal, there has to be some demineralization. So you have to have a demineralization and then the reverse, a reprecipitation will favor the incorporation of fluoride into the apatite crystal because fluoride is the most electro-negative of all elements and therefore bonds very firmly with calcium. The best time, the best time, for having this occur is actually right after tooth erupts. When a tooth erupts, it’s not yet fully maturated, in other words, it’s not yet fully calcified. It takes two more years for each tooth to calcify after it erupts into the oral cavity. That is the prime time for caries to occur because the tooth is very susceptible. It’s also the best time to apply fluoride, whether that be fluoride in a dentifrice or professional fluorides, and that’s true for both the primary dentition, the baby teeth, as well as the permanent dentition. So prematuration, post-eruptive, but prematuration is the best time to apply fluorides. That covers the period from two years of age up to about fifteen years of age, for different teeth in the oral cavity.

Following the ingestion of fluoride from a water, food, or supplement source, 86% to 97% of the element is absorbed in the stomach and small intestine. Fasting states (ingestion on an “empty stomach”) increases fluoride absorption, while the intake of other dietary nutrients such as calcium, aluminum, and magnesium tends to decrease fluoride absorption. Most of the fluoride absorbed systemically that is not excreted via normal pathways (i.e through the kidneys, the colon or by sweating) is deposited in mineralizing tissues such as bone and developing teeth. Fluoride is present in saliva at very low levels (0.01 ppm to 0.04 ppm) and in human milk at low levels (0.1 ppm). While the concentration of fluoride in these body fluids is minimal, studies show it is enough to impact dental caries.1