Calculus Composition — NDEB AFK MCQ
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Correct answer: C — Calcium phosphate (hydroxyapatite and other calcium phosphate salts)
Dental calculus is composed primarily of calcium phosphate mineral salts, mainly hydroxyapatite (~58%), with lesser amounts of octacalcium phosphate, whitlockite (β-tricalcium phosphate), and brushite. It forms by mineralisation of dental plaque through precipitation of calcium and phosphate from saliva (supragingival) or gingival crevicular fluid (subgingival). Calculus itself is not directly pathogenic but serves as a reservoir for bacterial plaque and is always covered by a biofilm layer.
Reference: Newman – Newman and Carranza's Clinical Periodontology, 13th ed., 2019