Effect of storage time and temperature change on the dimensional stability of polyvinyl siloxane and polyether impression materials: An in vitro study

Abstract

Background: Synthetic elastomers such as polyvinyl siloxane and polyether are the most commonly used impression materials. The accuracy and dimensional stability of these materials are influenced by the temperature, humidity, and storage time. Aim: The aim of this study was to assess the effect of storage time and temperature on the dimensional stability of polyvinyl siloxane and polyether impression materials. Materials and Methods: A stainless steel die was used to prepare the molds from three brands of polyvinyl siloxane (Elite HD, Express STD, Aquasil) and one brand of polyether (Impregnum F) impression materials. The samples were stored at five different temperatures (10°C, 180°C, 280°C, 350°C, and 450°C) for 24, 48, and 72 h, respectively. The linear change in the dimension of the materials were recorded and analyzed. Results: When stored at 280°C and 450°C, polyvinyl siloxane did not show any significant dimensional change in 24, 48, and 72 h when compared to control samples. At 10°C, significant dimensional change was noted in 24 h (P = 0.00) and at 180°C, significant change in the dimension was noted in 24 and 48 h (P = 0.01,P= 0.00, respectively). At 350°C, polyvinyl siloxane showed expansion in 24 and 48 h (P = 0.00,P= 0.04, respectively) whereas no further change occurred in 72 h. Significant changes in the dimensional stability were noted for polyether at all the five storage temperatures (10°C, 180°C, 280°C, 350°C, and 450°C) when compared to control samples. Conclusion: All the three brands of polyvinyl siloxane and the one brand of polyether tested showed statistically significant dimensional changes in 10°C, 180°C, 350°C, and 450°C, whereas at 280°C, all the tested materials showed no significant changes. Most of these changes occurred within 24 h, with very little changes occurring in 48 and 72 h.