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Mechanical property characterization of resin cement after aqueous aging with and without cyclic loading
Mary P Walker1, Paulette Spencer, J David Eick
1Department of Restorative Dentistry (Prosthodontics and Biomaterials), University of Missouri-Kansas City School of Dentistry, 650 East 25th Street, Kansas City, MO 64108-5419, USA. walkermp@umkc.edu
Objective:
The purpose of this study was to determine changes in flexural properties of resin cement under cyclic loading and aqueous aging.
Methods:
Panavia F flexural modulus and strength were measured by static loading to failure after 48-h, 31-d, and 60-d aqueous aging at 37 degrees C with and without cyclic loading at clinical stress levels. Six specimens were used for each experimental condition. Scanning electron microscopy (SEM) was also used to characterize the morphology of the fractured surfaces to potentially identify resin cement components particularly susceptible to degradation under simulated clinical function.
Results:
A two-factor ANOVA (p< or =0.05) and Least Significant Difference post hoc test indicated that cyclic loading produced a significant increase in the flexural modulus with no significant effect on the flexural strength. In contrast, aqueous aging time produced a significant decrease in flexural strength with no effect on the flexural modulus. The SEM fracture analysis indicated that resin matrix fracture occurred in static-aqueous specimens; while in the aqueous-cycled specimens, resin matrix fracture occurred in addition to an increasing proportion of filler/resin interface fracture as a result of both increased aqueous aging and increased flexural cycles.
Significance:
Evidence suggests that after aqueous aging with cyclic loading to simulate resin cement clinical function, initial degradation may be related to breakdown of the filler/resin interface bond. Such breakdown is potentially reflective of slow crack propagation that may contribute to in vivo resin cement cohesive failure.