MARGINAL FIT AND SURFACE-ROUGHNESS OF CROWNS MADE WITH AN ACCELERATEDCASTING TECHNIQUE

Statement of problem. Conventional investing and casting techniques fo llowing the manufacturers' recommendations are time-consuming. Acceler ated casting techniques have been reported, but their accuracy has not been adequately studied for complete crown castings. Purpose. This st udy evaluated the marginal fit and surface roughness of complete crown s made with a conventional and an accelerated casting technique. Mater ials and methods. Part I of the study determined the mean time interva l 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 tec hnique las recommended by the manufacturer) was compared with an accel erated technique that used 13- to 17-minute bench set time las determi ned in part I for each investment) and 15-minute wax elimination cycle in a 815 degrees C (1500 degrees F) preheated furnace. Part III evalu ated the surface roughness of castings made with the same techniques a s in part II. Results. For the marginal discrepancy and surface roughn ess, crowns fabricated with the accelerated casting technique were not significantly (P>0.05) different from those fabricated with the conve ntional technique. Conclusion. The accelerated casting technique descr ibed in this study could be a vital alternative to the time-consuming conventional techniques.