A flexible silicone impression material known for accuracy and dimensional stability?

• A. Crown
• B. Alginate
• C. Polyvinyl siloxane
• D. Impression tray

Answer: (C)

Impression materials must capture fine details and stay the same size after setting. Flexible silicone elastomers do this very well, with high accuracy and excellent dimensional stability because they cure with addition reactions (no by-products) and have strong elastic recovery. Polyvinyl siloxane, a addition-cured silicone, is especially prized for these traits, giving true reproduction of tooth surfaces and margins even after removal and repeated pours. That combination of precise detail capture and minimal distortion is what makes it the preferred flexible silicone impression material for final impressions. The other options aren’t impression materials: a crown is a tooth restoration, alginate is an easier-to-use preliminary impression material that is less dimensionally stable, and an impression tray is simply the container that holds the impression material.