Critical pH — NDEB AFK MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: D — 5.5
The critical pH for enamel demineralisation is approximately 5.5. When plaque pH drops below this level (due to bacterial acid production from fermentable carbohydrates), the oral environment becomes undersaturated with respect to hydroxyapatite, causing net mineral loss from enamel. Remineralisation occurs when pH rises above 5.5 and the environment becomes supersaturated. Fluoride lowers the critical pH to approximately 4.5 by promoting fluorapatite formation.
Reference: Fejerskov & Kidd – Dental Caries: The Disease and Its Clinical Management, 3rd ed., 2015