Flexural Strength of Interim Resin Materials for Fixed Prosthodontics

Purpose: Flexural strength of interim materials is of particular concern with long-span fixed partial dentures (FPDs) or in areas of heavy contact. The purpose of this study was to compare the flexural strength of seven resins used to fabricate interim fixed prostheses. Materials and Methods: Ten identical 25 x 2 x 2 mm specimens were made from seven interim materials (N = 70) (Trim, Acropars, Protemp 3 Garant, Unifast LC, TempSpan, Tempron, Duralay) according to ADA specification #27. After 14 days' storage in artificial saliva and thermocycling for 2500 cycles (5 degrees C to 55 degrees C), a standard three-point bending test was conducted on the specimens with a universal testing machine at a crosshead speed of 0.75 mm/min. The mean values of flexural strength of each interim material were calculated. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U-test, and the significance level was set at alpha = 0.05. Results: The lowest and highest flexural strengths were found for Trim from ethyl methacrylate resins and TempSpan from bis-acryl resins, respectively. The mean rank of flexural strength of the studied materials was TempSpan = 66.3, Protemp 3 Garant = 53.4, Tempron = 47.5, Duralay = 38.3, Unifast LC = 24.1, Acropars = 17.9, and Trim = 5.9. There was no significant difference between Tempron and Protemp 3 Garant, but the other resins were significantly different. Conclusions: Bis-acryl interim materials exhibited higher flexural strength than the methacrylate resins tested in this study. These higher values should be considered in making interim fixed prostheses, especially when long-term use or long-span FPDs are planned.