Diffusion of water in composite filling materials.

The uptake of water by composite filling materials seems to be a diffusion-controlled process; the magnitudes of the diffusion coefficients obtained are consistent with the uptake base through the resin matrix. The diffusion coefficients measured show the diffusion coefficient to decrease with increasing water concentration, which accounts for the protracted nature of the attainment of equilibrium uptake. Diffusion coefficients are generally lower in these composites based on difunctional methacrylates, compared with methyl methacrylate, presumably because of the highly cross-linked nature of the former.