The profile of surface roughness of zirconia ceramics polished with a pad (polisher) of acetate fiber is shown in Figure 6.16. Diamond and Cr2O3 abrasive powders of similar dimension were used, and a mirror-like surface was obtained in both cases. However a big difference was observed on the profiles of surface roughness. Sintered ceramics are heterogeneous in structure and are made up of fine crystals, boundaries, and pores. Smooth surfaces are obtained with diamond powders that function superiorly on stock removal and uniform removal of irregularities across a work surface. Cr2O3 powders, which are inferior to the diamond in stock removal, only attack weak parts of the work surface and make emphatic pits or dents in the profile of the surface roughness [22]. Some improvements can be expected by changing polishing materials to relatively hard metals such as tin and copper.