Iranian Dental Association Journal of Iranian Dental Association 3060-8201 31 3 2019 07 01 Comparison of Water Sorption of Two Injection Acrylic Resins with a Conventional Pressure-Packed Acrylic Resin 177 181 10.30699/jidai.31.3.177 EN Ehsan Ghasemi Ramin Mosharraf Siavash Mirzaei Journal Article 10.30699/jidai.31.3.177 2020 02 23 2020 02 23 Background and Aim: Water sorption is one of the most important properties that affects the quality of a prosthesis, and subsequently, the quality of treatment, and pa-tient’s quality of life. The aim of this study was to determine and compare the water sorption of two types of poly methyl methacrylate (PMMA) using the injection-molding systems with a traditional acrylic resin base material.<br> Materials and Methods: In this in vitro, experimental study, three groups of PMMA (n=10), consisting of two groups of injection molded PMMA samples (Vertex Castavar-ia and Ivo-Base High-Impact) were used for two different injection molding techniques and one group of conventional pressure-packed PMMA (Meliodent Heat Cure) was used for the conventional pressure-packed technique. After processing, 30 specimens were stored in distilled water at 37°C for 30 days. The water sorption test was then performed. Statistical analysis was carried out using SPSS version 23.0 via the Krus-kal-Wallis and Mann-Whitney tests (α=0.05).<br> Results: The mean value of water sorption was 17.88±1.08 µg/mm3 for IvoBase spec-imens, 28.45±2.19µg/mm3 for Vertex specimens, and 21.76 ±3.26 µg/mm3 for Melio-dent specimens (P<0.001 for Ivobase-Vertex, P <0.007 for Ivobase-Meliodent, and P<0.001 for Vertex-Meliodent).<br> Conclusion: Water sorption of IvoBase was significantly lower than that of other ma-terials. Despite such a significant difference, all of them completely fulfilled the re-quirements of EN ISO 20795-1:2008.