WEIBULL MODELS OF FRACTURE STRENGTHS AND FATIGUE BEHAVIOR OF DENTAL RESINS IN FLEXURE AND SHEAR

In estimating lifetimes of dental restorative materials, it is useful to have available data on the fatigue behavior of these materials, Cur rent efforts at estimation include several untested assumptions relate d to the equivalence of Raw distributions sampled by shear, tensile, a nd compressive stresses, Environmental influences on material properti es are not accounted for, and it is unclear if fatigue limits exist. I n this study, the shear and flexural strengths of three resins used as matrices in dental restorative composite materials were characterized by Weibull parameters. It was found that shear strengths were lower t han flexural strengths, liquid sorption had a profound effect on chara cteristic strengths, and the Weibull shape parameter obtained from she er data differed for some materials from that obtained in flexure, In shear and flexural fatigue, a power law relationship applied for up to 250000 cycles; no fatigue limits were found, and the data thus imply only one Raw population is responsible for failure, Again, liquid sorp tion adversely affected strength levels in most materials (decreasing sheer strengths anal flexural strengths by factors of 2-3) and to a gr eater extent than did the degree of cure or material chemistry. (C) 19 98 John Wiley Sr Sons, Inc.