Enamel Composition — MFDS Part 1 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 — Hydroxyapatite
The correct answer is D, hydroxyapatite. Mature enamel is highly mineralised, and its principal structural units are hydroxyapatite—or, more precisely, biologically substituted carbonated hydroxyapatite—crystallites. Fluoride can substitute for hydroxyl ions within the apatite lattice and increase resistance to acid dissolution, but fluorapatite is not the main bulk mineral of normal enamel. Carbonate is also present mainly as a substitution within apatite rather than predominantly as calcium carbonate. Octacalcium phosphate may act as a transient precursor during mineral formation, while tricalcium phosphate is another calcium phosphate compound but is not the principal mineral phase of mature enamel.
Reference: DeRocher KA et al. Chemical gradients in human enamel crystallites. Nature. 2020;583:66–71. https://pubmed.ncbi.nlm.nih.gov/32612224/