dental02.jpg (11342 bytes)Fundamentals of
Dental Materials

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Gypsum Products, Dental Waxes, and Impression Materials

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3-28. DIMENSIONAL STABILITY

During polymerization, synthetic rubber base impression materials undergo some shrinkage that continues for some time after the impression is made, particularly with the silicone type. However, these materials are not subject to syneresis and imbibition because they are hydrophobic (water-hating). They have more dimensional stability than do the hydrocolloids. They react to strain and stress in the same way the hydrocolloids do but do not change in volume. The cast must be poured within 30 minutes after an impression is made. This is necessary because the material continues to polymerize, and bubbles trapped in the material are apt to collapse causing the cast to be faulty. No separating material is required between the rubber base impression materials and the cast or die material.

David L. Heiserman, Editor

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Revised: May 22, 2017