The effect of fiber reinforcement on the fracture toughness and flexural strength of provisional restorative resins

Statement of problem. Fracture of provisional restorations is of concern, especially with long-span fixed partial dentures or areas of heavy occlusal stress. A number of different techniques for reinforcement of provisional restorations have been suggested; however, the effect of these techniques is largely unclear. Purpose. The aim of this study was to determine the fracture toughness and flexural strength of different types of provisional restoration resins reinforced with different commercially available fibers. Material and methods. A total of 105 specimens were prepared in this study for each test; compact tensile specimens for the fracture toughness test and rectangular specimens for the flexural strength test. The specimens were divided into 3 groups according to the type of resin used, jet, Trim, or Temphase (n=35), and then each group was divided into 7 subgroups (n=5) according to the type of fiber reinforcement, Construct, Fibrestick, Ribbond normal, Ribbond THM, Ribbond triaxial, or Fibrenet. Unreinforced specimens served as the control. Specimens were loaded in a universal testing machine until fracture. The mean fracture toughness (MPa(.)m(1/2)) and mean flexural strength (MPa) were compared by 1-way analysis of variance, followed by the Tukey standardized range test (alpha=.05). Results. Fibrestick and Construct reinforcements showed a significant increase (P < .0001) in mean fracture toughness over Unreinforced controls for all resins tested. Fibrestick increased the polymethyl methacrylate from 1.25 +/- 0.06 MPa(.)m(1/2) to 2.74 +/- 0.12 MPa(.)m(1/2); polyethyl methacrylate from 0.67 +/- 0.07 MPa(.)m(1/2) to 1.64 +/- 0.13 MPa(.)m(1/2); and bis-acryl from 0.87 +/- 0.05 MPa(.)m(1/2) to 1.39 +/- 0.11 MPa-in. Construct increased polymethyl methacrylate to 2.59 +/- 0.28 MPa(.)m(1/2) 1/2. polyethyl methacrylate to 1.53 +/- 0.22 MPa(.)m(1/2); and bis-acryl to 1.30 +/- 0.13 MPa(.)m(1/2); however, there was no significant difference between Fibrestick and Construct reinforcements in the degree of reinforcement. Similarly the mean flexural strength values were significantly increased by different combinations of fiber and resin (P < .0001). Conclusion. The addition of fibers to provisional resin increased both fracture toughness and flexural strength.