Time-dependent accuracy of elastomer impression materials. Part I: Condensation silicones.

1. Although condensation silicone elastomers can be used to produce multiple dies from a single impression, one can expect changes in dimensions of dies produced from successive pours. 2. Putty/wash systems exhibit variable behavior among different brands. Some products produce a series of dies of increasing diameter over a 4-day period, while other brands may produce a series of dies whose diameters decrease as they are successively poured. 3. Light-body wash silicone impressions made in adhesive-lined custom acrylic resin trays produce dies which increase in diameter with time. 4. Putty/wash system, in general, show a greater eccentricity of dies than is seen with custom-tray/adhesive/wash systems, but there were some significant exceptions among the brands tested. 5. There does not appear to be any difference in behavior between single-wash and double-mix techniques in the condensation-silicone systems. 6. For maximum accuracy, the condensation-silicone systems should be poured as soon as possible after making the impression.