The laboratory realization of the removal partial denture casting is often accompanied by casting defects. Among these casting defects, there are defects of structures that cause changes in the initial properties of the Cobalt chromium molybdenum alloy. 15 samples of Cobalt chromium molybdenum alloy metal frame fractured were recovered from dentists and prosthetists (some metal frames were used in the mouth; others not). They have been analyzed in the scanning electron microscope. The results of this study demonstrate the involvement of these defects of structures in the appearance of the fracture of the metal frame. Thus, we can conclude that to avoid this fracture, we need to improve manufacturing techniques of the metal plate in the laboratory.