The determination of elastic recovery of impression materials at the setting time

One of the prime requisites of an elastomeric impression material is that it should possess adequate elastic recovery on removal from undercut areas. Most standard methods of measuring elastic recovery rely on the preparation of specimens in moulds. The specimens are subsequently removed and subjected to compressive or tensile stresses several minutes after the setting time. The equipment described in this paper has been developed to enable elastic recovery values to be determined at times in the vicinity of the setting time. A shear strain is induced in the material for a short time and the resulting recovery recorded graphically. Results indicate that there is a significant improvement in elastic recovery from just prior to until just after the setting time.