Zinc Phosphate Exothermic Reaction — MFDS Part 1 MCQ

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ModerateDental MaterialsZinc Phosphate Exothermic ReactionMFDS Part 1

When hand-mixed, which dental material undergoes an exothermic acid-base setting reaction associated with the greatest temperature rise among these materials and is therefore traditionally mixed by adding powder incrementally over a broad area of a cool glass slab?

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Correct answer: E — Zinc phosphate cement

Zinc phosphate cement is correct. Its zinc oxide powder reacts with the phosphoric-acid liquid in an exothermic acid-base setting reaction. Comparative studies show that it produces a greater temperature rise than conventional glass-ionomer, polycarboxylate and zinc oxide-eugenol cements. During hand mixing, adding small powder increments over a broad area of a cool glass slab helps dissipate heat and control the reaction. Glass ionomer also sets by an acid-base reaction, but its temperature rise is substantially lower, making the original wording insufficiently discriminating. Zinc oxide-eugenol develops less heat. Composite resin setting is an exothermic polymerisation reaction rather than an acid-base reaction, while calcium hydroxide liners are not identified by this characteristic manipulation.

Reference: Duymus ZY, Yilmaz B, Karaalioglu OF. An investigation of thermal changes of various permanent dental cements. Dental Materials Journal. 2009;28(3):285–289. https://pubmed.ncbi.nlm.nih.gov/19662726/