Fracture toughness of acrylic denture base

This paper describes the application of two fracture toughness tests, the compact tension (CT) and the double torsion (DT) to homogenous poly(methyl methacrylate) and two-phase acrylics. Materials were tested in air as processed and after saturation for one month in water. Most materials gave stable crack propagation with these tests, allowing accurate measurement of crack velocity. Modulus and un-notched fracture strength (sigma f) were determined at an identical strain rate in bending to that used in the fracture toughness tests, allowing accurate calculation of the flaw size (a) for a material and an assessment of how applicable Linear Elastic Fracture Mechanics are to these materials.