Fluoride

Fluoride is a key agent in caries prevention, primarily due to its ability to inhibit demineralization and enhance remineralization of enamel. When present in low concentrations in saliva and plaque fluid, fluoride ions are incorporated into demineralized enamel surfaces during the remineralization process. This leads to the formation of fluorapatite - a more acid-resistant and less soluble crystalline form of apatite compared to hydroxyapatite, which naturally constitutes enamel.

The newly formed fluorapatite-enriched layer is not only more stable but also better able to protect the underlying lesion body from future acid attacks. Fluoride also strengthens enamel by binding with calcium ions, reducing the likelihood that calcium will be lost from the tooth during acidic challenges.

A significant benefit of fluorapatite is its ability to lower the critical pH for enamel dissolution. While demineralization of hydroxyapatite typically begins at a pH of around 5.5, fluorapatite resists acid dissolution until the pH drops closer to 4.5. This shift underscores fluoride’s protective role in maintaining enamel integrity in acidic conditions.

If fluoride is lacking in the oral environment, especially in the presence of frequent acid exposure from fermentable carbohydrates, the balance shifts toward demineralization and the risk for caries increases.

In the United States, fluoride is most commonly delivered through:

• Systemic sources, such as fluoridated community water supplies, and

• Topical sources, including over-the-counter or prescription fluoride toothpastes and mouthrinses.

For patients at higher risk of caries, professionally applied fluoride products - such as varnishes, gels, foams, or slow-release fluoride devices - may be recommended to provide enhanced protection and sustained therapeutic effects.