Casting of dental alloys: mold and alloy temperature effects

A casting monitor consisting of a square polyester grid pattern was used to evaluate the casting behavior of 6 non-precious dental casting alloys. A castability value, C v, was determined and is defined as the fraction or percentage of cast grid segments. The dependence of C v on the alloy superheat casting temperature, T a, and mold temperature, T m, was evaluated. It was found that the standard deviation (SD) of C v was dependent on C v. For curve fitting, a transformation, C v,t, of C v was used such that the SD(C v,t)≠f (C v,t). The transformed castability value is given by C v , t = ln ⁡ 2 / 3 + C v 2 / 3 + 1 / C v It was found that a single equation was capable of representing C v,t for all 6 dental alloys at the 95% confidence level: C v,t=a+bT a 1/2T m 2. This expression has many potential uses for alloy design, product quality assurance and dental laboratory casting control.