Enamel Demineralisation — MFDS Part 1 MCQ
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Correct answer: A — 5.5
The correct answer is A: pH 5.5. For caries-related mineral loss, enamel is conventionally considered at risk of net demineralisation when plaque pH falls to approximately 5.5; published estimates are commonly around 5.5–5.7 because the precise value depends on calcium and phosphate concentrations in plaque fluid. pH 6.5 is too high for the conventional enamel threshold, although dentine is more soluble and has a higher critical pH. pH 7.0 is approximately neutral. Values of 4.5 and 3.5 represent substantially stronger acid challenges rather than the point at which enamel first becomes susceptible. This threshold concerns caries-related plaque conditions; erosive dissolution does not have one universal critical pH because solution composition also affects mineral saturation.
Reference: Lussi A, Carvalho TS. Erosive tooth wear: a multifactorial condition of growing concern and increasing knowledge. Monographs in Oral Science. 2014;25:1–15. https://pubmed.ncbi.nlm.nih.gov/24993253/