Fluoride Mechanism of Action — NDEB AFK MCQ
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Correct answer: D — Promotion of remineralisation and formation of fluorapatite
The primary caries-preventive mechanism of fluoride is the promotion of remineralisation and formation of fluorapatite. When fluoride is present in saliva and plaque fluid at the enamel surface, it enhances the precipitation of calcium and phosphate ions back into demineralised enamel, forming fluorapatite [Ca₁₀(PO₄)₆F₂], which is more acid-resistant (critical pH ~4.5) than hydroxyapatite (critical pH ~5.5). Fluoride also inhibits bacterial enzyme activity (enolase in glycolysis) at higher concentrations.
Reference: Fejerskov & Kidd – Dental Caries: The Disease and Its Clinical Management, 3rd ed., 2015