The mechanical reliability and aesthetic appearance of ceramic dental prostheses are strongly influenced by the presence of defects. When several processes are used during fabrication of ceramic dental prostheses, additional defects are unavoidably introduced in each process step; these are in addition to the ones that already exist in raw materials. To avoid the degeneration of material performance by the accumulated defect population, process optimization is needed to minimize the defects introduced. Standardized mechanical evaluations are usually performed on samples with carefully prepared surfaces in order to minimize the influence from the defects usually induced by fabrication processes. The results from such mechanical evaluation indicate the strength level that is achievable by the material with the given population of bulk defects. In order to avoid a reduction in the performance of the ceramic material by the additional defects normally induced by the fabrication process, it must be understood how these defects are introduced, and solutions must be found to reduce their size and frequency through modifications of the material and processes. The aim of this chapter is to elucidate the sources of defects that are common for ceramic dental prostheses and to determine how to minimize them.