Fracture toughness of provisional resins for fixed prosthodontics.

Six resins for treatment restorations were tested to determine fracture resistance. The resins were broadly categorized chemically as: one epimine, two poly(methyl methacrylate)s, one composite, and two poly (R' methacrylate)s. Miniature compact tension specimens were molded and then cured for 5 minutes at atmospheric pressure or at an additional pressure of approximately 0.14 MPa. A commercially available pressure vessel was used for curing. The epimine and two poly(methyl methacrylate) resins demonstrated the greatest fracture toughness whereas poly (R' methacrylate) had the lowest. The composite, representing a new class of provisional material, recorded an intermediate fracture toughness. The use of a pressure vessel during polymerization did not significantly increase the fracture toughness of the six resins. There was minimal effect of pressure on the surface of the specimens but it reduced the internal porosity evident in the atmospheric pressure-cured specimens.