[Quantitative evaluation by measuring affected area for cytotoxicity of dental materials]

The agar overlay method was modified and employed in this study to quantitatively evaluate the cytotoxicity of dental materials. The area of fibroblasts affected by the release of toxic substances from tested materials was determined with an image analysis system in order to compare the relative cytotoxicity of amalgams and composite resins. The cytotoxicity of amalgams decreased by 50% or more with aging time. Zinc appeared to be the major contributor to the cytotoxicity of amalgams. The cytotoxicity of chemically cured composite resins was also reduced with hardening time. However, even after 24 hours, the cytotoxicity of all chemically cured composite resins was still apparent. The cytotoxicity of light cured composite resins was dramatically reduced after illumination with the light source. The cytotoxicity of both amalgams and composite resins was strongly dependent upon their hardening process, since aging and curing produced a more stable material which was less likely to release toxic substances into the culture medium. The technique developed in the present study for measuring the area of affected cells to quantitatively evaluate the cytotoxicity of dental materials is simple and reproducible.