Enamel Water Content — MFDS Part 1 MCQ

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ModeratePhysiologyEnamel Water ContentMFDS Part 1

For mature permanent human enamel, what is the approximate free or removable water content by weight, excluding tightly bound or constitutional water?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: D — 1–2%

Explanation lettering: D = shown as A · E = shown as B · B = shown as C · A = shown as D · C = shown as E

The correct answer is A. Direct measurements of mature permanent human enamel place its free or removable water content at approximately 1% by weight, with reported values around 0.9–1.15%; therefore, 1–2% is the best approximation. Higher estimates can arise when tightly bound interstitial or constitutional water is included. In particular, NMR studies have identified a larger bound-water component in addition to approximately 1–2% semiliquid water. Consequently, options B–E overestimate the free/removable fraction specified in the stem. The distinction is important because an unqualified question about total enamel water is method-dependent and could make values in the 5–7% range appear defensible.

Reference: Bonte E, Deschamps N, Goldberg M, Vernois V. Quantification of free water in human dental enamel. Journal of Dental Research. 1988;67(5):880–882. https://pubmed.ncbi.nlm.nih.gov/3284940/