Evaluation of the elastic recovery of polyether impression materials

Purpose: To evaluate and compare the effects of induced strain, time of straining, and loading time on the elastic recovery of two polyether impression materials and a vinyl polysiloxane reference material. Methods: Specimens of the light and heavy-bodied types of the polyether materials P2 (P2L/H) and Impregum (IML/H) and of the vinyl polysiloxane impression material Flexitime (FLC/H) were loaded in a cone-plate rheometer with tensile strains between 16.4 and 60%, at different times after mixing, and at loading times between I and 10 seconds. The resulting permanent deformation was determined from creep curves. For each material and each variable condition six specimens were tested at ambient laboratory atmosphere. Regression analyses and ANOVA were used for statistical data analysis. Results: Both induced strain, time of straining, and straining rate were significantly associated with the resulting permanent deformation of all materials, except FLC when loaded in the well-set stage between 1 and 10 seconds loading time at 37.4% induced tensile strain (P < 0.001). Apart from P2 the heavy-bodied impression materials showed significantly higher secondary creep (P < 0.05) than their corresponding light-bodied versions.