Background: Casting is one of the most popular processes for preparation of dental appliances and structures. The effect of melting and casting process on the corrosion behavior of dental appliances and prosthetics is important since the corrosion behavior of the dental metallic alloy is an indication of their biocompatibility in the mouth. The aim of this investigation was to evaluate the effect of laboratory casting and the recasting and use of return materials on the corrosion resistance of dental casting alloys.Materials and Methods: The ingot of two types of dental alloys (Co-Cr-Mo and Ni-Cr- Mo alloys) were used and enough coupons were prepared using the lost wax molding technique and centrifugal casting process. The same process, using remelting and recasting of the alloys, was performed to prepare the other samples for evaluating the effect of the recasting and use of casting returns and scrape materials on the corrosion resistance of the casting alloys. Electrochemical potentiodynamic tests were performed in physiological solution in order to determine and compare the corrosion behavior of dental casting alloy samples as an indication of biocompatibility.Results: The results showed no statistically significant difference between the mean corrosion current density values of two groups of the Cr-Co-Mo alloy (melted once and melted four times). There were statistically significant differences between the mean corrosion current density values of three groups (melted once, melted four times, and melted five times) of the Ni-Cr-Mo alloy (p<0.05). The five times melted dental casting alloy possessed the lowest corrosion resistance. This was due to the undesired effect of recasting process on the corrosion characteristics of dental casting alloys and it seems that the condition and parameters of the casting process is not stable every time.Key words: Biocompatibility, Corrosion resistance, Dental alloy, Laboratory casting