Linear thermal contraction of impression materials has been measured in the 40-18 ~ temperature range immediately after the polymerization shrinkage. Samples of 2 cm in length have been analysed by a scanned laser beam micrometer and the coefficient of thermal contraction has been calculated. Silicone-based specimens of different viscosities have been tested. The temperature-induced shrinkage has been compared with the time-dependent shrinkage.PACS 87.90 -Other topics in biophysics, medical physics, and biomedical engineering. PACS 81.70 -Materials testing. PACS 65.70 -Theoretical expansion and thermomechanical effects.

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