Fracture toughness of packable and conventional composite materials

Statement of problem. The introduction of packable composite has expanded the choices of materials for the restoration of posterior teeth. Few independent studies are available on the fracture toughness (K-IC) of the presently available packable composites compared with more conventional composite alternatives. Purpose. This investigation evaluated the relative fracture toughness of 3 packable composites, 2 conventional composites, and 1 laboratory-processed composite. Material and methods. Six composite materials were tested in this study. These included: 3 packable composites (Alert, SureFil and Solitaire), 2 conventional composites (Herculite and Heliomolar), and 1 laboratory-processed composite (Belleglass). K-IC was determined by preparing 8 mini-compact test specimens (8.2 mm diameter x 2 mm thickness) for each composite in a polytetrafluoroethylene split-mold with introduced precracks created with a razor blade. Specimens were stored in distilled water at 37degrees +/- 2degreesC for 7 days. Testing was performed on a universal testing machine at a displacement rate of 0.5 mm/min until fracture. Analysis of variance (P<.0001) and Ryan-Einot-Gabriel-Welsch multiple range tests (P<.05) were performed on all data Results. The mean fracture toughness of Alert (1.57 Mpa(.)m(1/2)) was significantly greater than any of the other composites tested. Solitaire, a packable composite, exhibited a mean fracture toughness (0.67 MPa(.)m(1/2)) that was significantly lower than any of the other materials tested. No significant difference was noted between Belleglass (1.27 MPa(.)m(1/2)), SureFil (1.25 MPa(.)m(1/2)) and Herculite (1.16 MPa(.)m(1/2)). Conclusion. Within the limitations of this study, the glass fiber-reinforced packable composite exhibited improved fracture toughness when compared with the other composite materials tested.