Determination of the accuracy of three die systems

This article reports the findings of two interrelated projects that measured the accuracy of electroplated, epoxy resin, and polyurethane die materials against a master tooth, using the Michigan Computer Graphics Coordinate Measuring System (MCGCMS). In the first phase, on occlusal die morphology, replications of a master tooth were used to validate the MCGCMS reliability. Eighteen total data sets derived from three silver-plated dies and three epoxy resin dies were then compared with a representative data set of the master tooth. The mean differences for all silver-plated die and epoxy die measurements against the master ranged from -42 to -49 and -46 to -230 microns/mm2, respectively. In the second phase, two epoxy die materials and a polyurethane system were compared with a master tooth in an identical manner. In paired comparisons to the master tooth, mean differences for Epoxydent material, epoxy resin, and polyurethane dies ranged from -147 to -153, -149 to -230, and -56 to -168 microns/mm2, respectively. A Student t test using a CLR ANOVA was performed between the master tooth and the five die systems. A significant difference was revealed between the enamel-silver difference and the enamel-Epoxydent difference data at the 95% confidence level. A significant difference also occurred between enamel-silver and enamel-epoxy resin. It was concluded that silver-plated dies are acceptable replicas of a master tooth. Epoxydent and epoxy resin dies did not provide reliable replications when compared with the silver-plated dies. Epoxy and polyurethane replications, although reported as accurate, were inconclusive.