Abstract
The dynamic impression material changes in its physical properties with the lapse of time after mixing. To make clear such changes, the author measured relaxation of the trially made dynamic impression materials with a relaxometer and examined their viscoelastic behaviors. The results will be given in the following : 1. There are two types of commercial dynamic impression material. In one of them, relaxation time is extented, while in the other, reduced with a rise in modulus of elasticity. 2. The effect of ethanol in the mixing liquid on the mixture of the trially made dynamic impression material is that it acts as an accelerator at the initial period of hardening and as a plasticizer at the subsequent period.
