Compressive creep of denture base polymers

The creep characteristics of heat-polymerized and auto-polymerized dough and pour type denture base materials were measured at 23,37, and 50 degrees C with emphasis on secondary steady state creep rates. The creep rates were correlated to the processing conditions and material composition. Two different creep mechanisms were evident, depending on the stress levels. Below 20-40 M Nm-2 at 37 degrees C, the creep was due to a homogeneous deformation. At higher stress levels the creep was ascribed to an inhomogeneous deformation mechanism. The lowest creep rates were found for the heat-polymerized materials. Variations in the creep rates for the other materials could generally be related to composition differences.