Basic Study of Sintered Metal Restoration: Part 2 Metallographic Examination

Though cast restoration is the major skill to make prosthesis today, sintered metal restoration by brush application is being investigated and has wide possibilities. As metallographic examination, sintered specimens (S) and conventional cast specimens (C) were compared by SEM observation, X-ray mappings and volume of surface roughness. The results were as follows: 1. In comparison of surface roughness of polished cutting surfaces after casting, surface roughness C was smaller than S. SEM observation showed few micro pits on the S surface, and there were some spaces which were supposed to be gas holes. While the cutting surface of C was generally rough, the S surface showed brush streaks and indentations which averaged 3μm in depth, in the intergranular area. 2. After the corrosion test in aqua regia, both C and S showed corrosion on the polished surface. The intergranular area was corroded on the C surface and showed tortoise-shell pattern, and selective corrosion was observed inside the crystal grain. There were fusions and spaces between alloy grains of S, and the width of the space was smaller than that of C. No element was found in this space by elementary analysis, hence these spaces were empty. As for the results of surface roughness, S was smaller than C. Based on these results, it is suggested that the corrosion resistance of S is superior to that of C from the metallographical point of view.