Tensile elastic recovery of elastomeric impression materials.

摘要

STATEMENT OF PROBLEM: Currently, a standard protocol exists to measure the elastic recovery of impression materials from compressive strain; however, no protocol exists for the measurement of elastic recovery from tensile strain. PURPOSE: The purpose of this study was to compare elastic recovery from tensile strain test with the ISO elastic recovery test for 5 vinyl polysiloxane materials (Aquasil Ultra, Examix, Genie, Imprint 3, and StandOut) and 1 hybrid material (Senn). MATERIAL AND METHODS: Specimens (n=5) were fabricated in a brass mold and loaded in tension with a crosshead speed of 300 mm/min to 50% or 100% strains. Two hours following specimen elongation, the change in length of the specimens was measured. Additional specimens (n=5) were tested in tension until failure at 200 mm/min. The maximum elongation at failure was recorded. Elastic recovery specimens (n=4) were prepared for each material following ISO standard 4823. The change in dimension of these specimens was measured following a 30% compressive strain. Group means were compared using 1-way ANOVA and Tukey-Kramer HSD test (alpha=.05). Correlation between different tests was evaluated using Pearson's correlation coefficient. RESULTS: Vinyl polysiloxane materials of varying composition demonstrated significantly different elastic recovery, and the hybrid material demonstrated the least elastic recovery in both tests. All materials exceeded a 100% elongation before failure. Significant linear correlation was found between means of the ISO method and those of a 100% tensile strain (r(2)=0.69, P=.039), but not those of a 50% tensile strain (r(2)=0.56, P=.086). CONCLUSIONS: Elastic recovery from compressive strain can only partially predict elastic recovery from tensile strain, suggesting that elastic recovery from tensile strain is a relevant test.