An investigation into the permeability of composite materials using silver nitrate

A new effect of silver-nitrate staining on dental composites and unfilled polymers has been observed which may be useful in the study of polymer permeability. After extended storage in silver nitrate, the materials developed a layer of brown stain in the subsurface. The color was thought to be caused by the presence of finely divided silver precipitated in microcavities within the composite. Energy Dispersive Analysis by x-ray confirmed the presence of silver in the stained zone. The width and shade of staining varied in different materials. After 90 days, layers of different shades could be seen within the stained zone. The exact shade of the stain is thought to depend upon the size of the precipitated silver particles, which is directly related to the sizes of the microcavities.