Flexural Strength of Resins Used to Fabricate Provisional Restorations

Introduction: There are essentially two classes of materials that can be used to fabricate provisional restorations. Conventional acrylic resins are known for their ease of use and low cost, whereas bis-acrylic resins are known for their higher strength and better polishing properties. Objectives: The objective of this study was to compare the flexural strength of five bis-acrylic and three acrylic resins. Methods: Six bars measuring 25mm x 6mm x 4mm were made of (1) Structur 2, Voco; (2) Protemp 4, 3MESPE; (3) Luxatemp fluorescence, Dmg; (4) Systemp c&b, Ivoclar; (5) Telio cs c&b, Ivoclar; (6) Dencor, Clássico; (7) Dencrilay, Dencril and (8) Duralay, Reliance. Bars were fabricated in a bronze split mould placed between two glass slabs covered with acetate foil. After manipulation according to manufacturer's instructions, materials were injected into the moulds and placed in a press at room temperature for 1h. After 1h moulds were opened and bars were placed in a water bath at 37˚C for 23h. All bars were tested in a universal testing machine with a 1 kN cell with a 2mm/min crosshead speed in a 3-point bend test with a 20mm span. Results were analyzed with ANOVA followed by Tukey post-hoc test at p=0.05. Results: Protemp 4 had a significantly higher flexural strength compared to all other bis-acrylic resins. There was no significant difference between Protemp 4 and two acrylic resins (6, 7). There was one bar of Dencor that warped and did not fracture. Conclusions: Within the limitations of this study it can be concluded that one bis-acrylic resin demonstrated the highest values for flexural strength. Some specimens of acrylic resins deformed and did not break which may explain some of the high flexural strength values. (This study was partially supported by 3M ESPE, Seefeld, Germany)