Addition Silicone Properties — MFDS Part 1 MCQ

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ModerateDental MaterialsAddition Silicone PropertiesMFDS Part 1

A definitive elastomeric impression for fixed prosthodontics must be disinfected and transported to the dental laboratory, so pouring may be delayed for several hours. Compared with condensation silicone, which property most directly makes addition silicone (polyvinyl siloxane) more suitable in this situation?

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Correct answer: B — Superior dimensional stability

The correct answer is B: superior dimensional stability. Addition silicone does not produce the volatile alcohol by-product responsible for continuing shrinkage in condensation silicone. It therefore undergoes less post-setting dimensional change and is better suited to delayed pouring or transport to a laboratory. Addition silicone is generally more expensive, so B is incorrect. Working and setting times vary between formulations and a shorter working time would not explain stability during storage. Tear strength may differ between products, but it is not the principal advantage relevant to delayed pouring. Conventional silicones are intrinsically hydrophobic; surfactants can improve the wettability of some modern addition silicones, but greater hydrophilicity is not the defining advantage over condensation silicone.

Reference: Naumovski B, Kapushevska B. Dimensional Stability and Acuracy of Silicone-Based Impression Materials Using Different Impression Techniques: A Literature Review. Prilozi. 2017;38(2):131-138. https://pubmed.ncbi.nlm.nih.gov/28991761/