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How does fluoride help protect tooth enamel from decay?

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A labeled diagram of the periodic table entry for fluorine, showing its atomic number 9, symbol F, atomic weight 18.998, electron configuration, and indicating it is a halogen and a gas at room temperature. — fluorine Properties of fluorine.

Fluoride protects tooth enamel from decay through two primary mechanisms:

Remineralization: At the tooth surface, fluoride facilitates the attachment of calcium and phosphate ions, which promotes the formation of fluorapatite crystals. This process helps to remineralize and strengthen enamel.1
Inhibition of Bacteria: Fluoride present in saliva reduces the growth and adhesion of bacteria that contribute to tooth decay. It achieves this by blocking the activity of specific enzymes, which decreases the production of acid that would otherwise damage the teeth.1

By both repairing the enamel structure and limiting the bacterial activity that causes cavities, fluoride serves as a critical component in maintaining oral health.12