Fluoride in the Body and its Role in Enamel Development

Fluoride becomes integrated into the inorganic component of enamel, specifically the apatite lattice, by replacing either hydroxyl or carbonate ions. This integration requires some demineralization of the already developed apatite crystal. The process involves demineralization followed by reprecipitation, which promotes the incorporation of fluoride due to its high electronegativity, allowing it to bond strongly with calcium. The optimal time for this incorporation is right after a tooth erupts, as it is not yet fully matured or calcified; this process can take up to two additional years for each tooth. During this period, the tooth is particularly vulnerable to caries, making it an ideal time for fluoride application, whether through toothpaste or professional treatments. This recommendation applies to both primary (baby) and permanent dentition, highlighting that the best time for fluoride use is during the prematuration phase, which spans from around two to fifteen years of age, depending on the specific teeth involved.

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