Alginate Dimensional Stability — NDEB AFK MCQ

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ModerateDental MaterialsAlginate Dimensional StabilityNDEB AFK

Which impression material undergoes imbibition (swelling) if left in water too long before pouring?

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

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Correct answer: D — Alginate (irreversible hydrocolloid)

Alginate (irreversible hydrocolloid) is an aqueous-based material that absorbs water (imbibition) if stored in water, causing dimensional changes and distortion. If exposed to air, it loses water through evaporation (syneresis), causing shrinkage. Alginate impressions should be poured within 10-15 minutes or stored briefly in a sealed plastic bag with a damp paper towel (not immersed in water). Addition silicones are dimensionally stable and can be delayed before pouring.

Reference: Anusavice – Phillips' Science of Dental Materials, 13th ed., 2022