Staining of in vivo subsurface degradation in dental composites with silver nitrate

A previously reported technique for staining areas of degradation in dental composite restorations was evaluated in 51 removed restorations. The staining reagent was silver nitrate, which penetrated the degraded subsurface as ionic silver and was subsequently developed into colored deposits of metallic silver. Several artefacts were recognized that resulted in an apparent image of subsurface stain. Most importantly, the presence of a layer of adsorbed silver on the edge of the specimen exaggerated the extent of staining. In order for the true depth of stain to be determined, thin sections of the materials should first be examined with a stereomicroscope to distinguish any contribution from adsorbed silver on the specimen edge. With this regimen, no stain was present in 41% of the restorations, and in a further 30%, the depth of stain was less than 50 microns. In two composites, the depth of stain was greater than 900 microns, and in a number of specimens, localized stain was found in association with attrition scars. Energy-dispersive x-ray analysis indicated that the amount of silver present in the degraded layers was very small. Overall, the results indicated that the staining technique is useful in the study of composite degradation.