Comparison of Dimensional Changes and Water Absorption of Three Acrylic Resins Used for Provisional Fixed Restorations

Autoploymerized acrylic resins are used for construction of fixed provisional restorations. The linear polymerization shrinkage and water absorption are the critical factors in the desired properties of such restorations. The aim of the present study was to compare the dimensional changes and water absorption of three fixed provisional acrylic resins،Trim II، Tempron، and Acroprars TRII. In this experimental study، 90 acrylic samples (20 mm × 12 mm × 3 mm) were made by a metal mold (30 samples in each group). Then، each group was randomly divided into two equal groups. Dimensional changes of the samples were measured immediately after polymerization and seven days post curing. The data were analyzed by one way ANOVA and T-test. Acropars TRII resin exhibited the highest dimensional changes and water absorption. The lowest mean values were recorded for Tempron samples. One week after polymerization، no statistical difference was found between the dimensional changes of Trim II and Acropars TRII. Linear dimensional changes of all the used acrylic resins were less than 2%. It seems that water absorption of acrylic resins can compensate the polymerization shrinkage. This effect was more significant for samples made by Acropars TRII than the other tow groups. Clinically، linear dimensional changes of the three acrylic resins were acceptable.