Impression Material Accuracy — MFDS Part 1 MCQ

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EasyDental MaterialsImpression Material AccuracyMFDS Part 1

A definitive impression is required for a tooth-supported fixed prosthesis in a dentate arch with undercuts. Which impression material provides the best combination of dimensional stability, elastic recovery and fine-detail reproduction?

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Correct answer: C — Addition-cured silicone (polyvinyl siloxane)

Addition-cured silicone (polyvinyl siloxane) is the best answer. It reproduces fine detail, has excellent elastic recovery and undergoes little dimensional change because its setting reaction does not normally produce a volatile by-product. These properties make it appropriate for definitive fixed-prosthodontic impressions involving tooth undercuts. Condensation-cured silicone releases an alcohol by-product and therefore contracts more during storage. Alginate is convenient and elastic but is less dimensionally stable because water loss or uptake causes syneresis or imbibition. Zinc oxide-eugenol paste can record edentulous soft tissues accurately but is rigid after setting and cannot be safely removed through dentate undercuts. Impression compound is also rigid after cooling and has comparatively poor fine-detail reproduction and dimensional stability.

Reference: Madanshetty P et al. Addition Silicone Impressions in Fixed Prosthodontics: Clinical Standpoints. 2023. https://pubmed.ncbi.nlm.nih.gov/28991761/