introduction: discoloration of dental composite resins is one of the most common reasons for replacement of these restorations. this in vitro study was carried out to evaluate the effect of aging on discoloration of silorane-based filtek p90 and micro-hybrid z250 composite resins. materials and methods:   this experimental study was carried out on 10 disk-shaped filtek p90 and z250 samples, mea...

The aging-time dependence of the segmental relaxation time of poly(vinyl acetate) (PVAc) in the glassy state is investigated in the bulk polymer and its nanocomposites with silica (SiO(2)). These systems present identical segmental dynamics, when this is probed in the equilibrium supercooled liquid by broadband dielectric spectroscopy. An acceleration of the physical aging process of PVAc with ...