Compressive Creep of Dental Composites

¹ Department of Prosthodontics, College of Dentistry, University of Illinois at Chicago, Chicago, Illinois 60612
² Council on Dental Materials, Instruments, and Equipment, American Dental Association, and American Dental Association Health Foundation, Chicago, Illinois 60611

The creep compliance curves for P-10, Adaptic, and Silar composite materials were obtained at 23°C, 37°C and 50°C and at a number of initial stress levels ranging from 5 to 75% of their compressive strengths. The creep compliance curves were characterized by large instantaneous compliances, followed by retarded strain compliances with very minimal viscous flow. Rupturing occurred only at the higher stresses and temperatures, and was characterized by a sharp upsurge in the compliance just before failure. Empirical curve-fitting of the data indicated that the creep compliances exhibited a very good representation when plotted against log t.

Both isochronous stress-strain and isochronous compliance-stress diagrams indicated that linear visco-elasticity was followed below the stress of about 70-100, 50-70, and 120-<240 MPa for Silar, Adaptic, and P-10, respectively. The combined Voight-Maxwell linear visco-elastic model was used to describe the compliance curves. At higher stresses, where compliance was dependent upon stress, a nonlinear visco-elastic model based upon Eyring's thermally activated process was considered.