Marginal fit and surface roughness of crowns made with an accelerated casting technique

Abstract

Statement of problem. Conventional investing and casting techniques following the manufacturers’ recommendations are time-consuming. Accelerated casting techniques have been reported, but their accuracy has not been adequately studied for complete crown castings. Purpose. This study evaluated the marginal fit and surface roughness of complete crowns made with a conventional and an accelerated casting technique. Materials and methods. Part I of the study determined the mean time interval required for each investment to reach its maximum exothermic setting reaction temperature. Part II determined the marginal discrepancy of standardized complete crowns cast in a high noble metal ceramic alloy, with the use of four phosphate-bonded investments. A conventional technique (as recommended by the manufacturer) was compared with an accelerated technique that used 13- to 17-minute bench set time (as determined in part I for each investment) and 15-minute wax elimination cycle in a 815°C (1500°F) preheated furnace. Part III evaluated the surface roughness of castings made with the same techniques as in part II. Results. For the marginal discrepancy and surface roughness, crowns fabricated with the accelerated casting technique were not significantly ( P>0.05) different from those fabricated with the conventional technique. Conclusion. The accelerated casting technique described in this study could be a vital alternative to the time-consuming conventional techniques. (J Prosthet Dent 1998;80:337-45.)