Abstract
In previous studies, the present authors examined the discoloration of esthetic restorative materials, which might be mainly caused by the condition of the elements of the materials and the hydrogen sulfide gas. From the results of those studies, the causes of the discoloration were, supposedly, not only the combination of the elements and the hydrogen sulfide gas but also the physical aspects of the specimens: surface conditions, structures and properties. They measured the surface roughness of the specmiens to estabish the relationship between the color shift and the surface conditions. They further confirmed the existence of sulfur on the surface of the specimens, and examined the relationship among the discoloration, structures and properties of the specimens. The results were as follows: 1. The surface roughness of the specimens exposed to the hydrogen sulfide gas showed larger roughness than that of the specimens exposed to the air. 2. The two-dimensional analysis by an electron microprobe x-ray analyzer detected more sulfur in all of the specimens exposed to the hydrogen sulfide gas. Thus detected sulfur on the specimens exposed to hydrogen sulfide gas showed no significant difference in its concentration and distribution, that might clearly indicate that the hydrogen sulfide gas generated the sulfide on the surface of the specimens which had nothing to do with the color differences.
