Effect of filler size and morphology on viscoelastic stability of resin-composites under dynamic loading.

Effect of variation in filler particle size, morphology and wet conditioning on the viscoelastic stability of resin-composites under dynamic loading was investigated. Eight experimental light cured resin-composites were selected. For each of the eight resin-composites, ten cylindrical specimens (4 × 6 mm), divided into two subgroups (n = 5) were prepared. Group 1 and 2 were loaded dynamically after 1 day of dry storage and 1 week of wet storage, respectively. A cyclic load between 1 and 50 MPa was applied for both groups at a frequency of 0.25 Hz for 30 min to obtain the 'dynamic' creep strain (%). Data was analysed by univariate ANOVA. Unimodal spherical and irregular resin-composites showed a significant influence of particle size and shape on dynamic creep under dry condition, but not for wet conditions. Irregular filler particles in both unimodal and multimodal resin-composites were more resistant to dynamic creep under wet conditions and showed higher stiffness.