Impression Material Stability — ORE Part 1 MCQ

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EasyDental MaterialsImpression Material StabilityORE Part 1

Which of the following impression materials has the property of being able to be poured multiple times without loss of accuracy?

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Correct answer: C — Addition silicone (polyvinyl siloxane)

Addition silicone (polyvinyl siloxane) is the only material in this list with the demonstrated ability to yield multiple accurate casts from a single impression. All addition-cured silicone materials exhibit excellent dimensional stability over extended storage times, with minimal dimensional change whether poured immediately or after delay, allowing multiple pours without clinically significant loss of accuracy. Alginate (option B) loses accuracy progressively with time elapsed. Condensation silicone (option C) shows rapid loss of accuracy with delayed pouring, limiting it to immediate use. Zinc oxide eugenol (option D) and agar (option E) lack the dimensional stability required for repeated pouring. This property—the ability to produce multiple accurate dies from one impression—is a key clinical advantage of addition silicones in prosthodontic practice.

Reference: Perakis N, Belser UC, Magne P. Final impressions: a review of material properties and description of a current technique. Int J Periodontics Restorative Dent. 2004 Apr;24(2):109–117. PMID: 15119881; and Johnson GH, Craig RG. Accuracy of four types of rubber impression materials compared with time of pour and a repeat pour of models. J Prosthet Dent. 1985 Feb;53(2):484–490. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10517288/