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Fluoride Mechanism — MFDS Part 1 MCQ

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ModeratePhysiologyFluoride MechanismMFDS Part 1

During repeated falls in plaque-biofilm pH following dietary sugar exposure, which action best explains the principal post-eruptive cariostatic effect of low concentrations of fluoride in oral fluids?

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Correct answer: B — Inhibiting apatite dissolution during acid challenge and accelerating remineralisation when pH recovers

Option B is correct. Fluoride's principal caries-preventive effect is topical and post-eruptive. At low concentrations in plaque fluid, fluoride associates with apatite crystal surfaces during a fall in pH, reducing mineral dissolution. As pH recovers, it accelerates redeposition of calcium and phosphate; the repaired mineral preferentially contains fluoride and is less soluble during subsequent acid challenges. Fluoride does not sterilise plaque: any antimicrobial activity at clinically encountered concentrations is subsidiary and does not eliminate acidogenic organisms. It does not directly stimulate sustained salivary secretion, produce new enamel thickness after eruption, or prevent pellicle and plaque-biofilm formation. This is more accurate than implying wholesale conversion of enamel into pure fluorapatite.

Reference: Šutej I, Bašić K, Peroš K. The Cariostatic Mechanisms of Fluoride—An Updated Review. Dentistry Journal. 2026;14(7):390. https://pubmed.ncbi.nlm.nih.gov/42505698/