The wear of enamel when opposed by different ceramic systems was investigated by use of an artificial oral environment. Cerestore, Dicor, and Ceramco discs were opposed by recently extracted natural teeth. The samples were exposed to 300,000 defined mastifactory cycles under physiologic conditions. It was found that the wear mechanisms for Cerestore and Ceramco porcelains were similar, but were distinctly different from that of Dicor. The total volume loss of enamel was 50% less when opposed by Dicor, than when opposed by either the Cerestore or Ceramco porcelains. None of the samples had any external shade applied to their surfaces.