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Zinc Phosphate Cement pH — NDEB AFK MCQ

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ModerateDental MaterialsZinc Phosphate Cement pHNDEB AFK

Which of the following dental cements has the lowest pH during setting and is therefore most irritating to the pulp?

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

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Correct answer: A — Zinc phosphate cement

Zinc phosphate cement has the lowest initial pH during setting (~3.5 at 5 minutes, rising to ~7.0 after 24-48 hours). This highly acidic initial pH can cause significant pulp irritation if placed in direct contact with the pulp or very thin dentin. A protective liner (calcium hydroxide or RMGIC) is recommended under zinc phosphate cement in deep cavities. GIC has an initial pH of ~2-3 but rapidly rises; zinc polycarboxylate has a low initial pH but is less irritating due to the high molecular weight of polyacrylic acid (cannot penetrate tubules).

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