Comparison of dimensional accuracy of four different die materials before and after disinfection of the impression: an in vitro study

This study was conducted to compare the linear dimensional accuracy of die materials before and after disinfection of the impression. Type IV and V conventional dental stone, type IV-resin impregnated and copper-plated die materials were studied. A stainless-steel master die analogs to a complete veneer crown preparation with three scribed lines (I: vertical, II and III: horizontal) was machined and measurements were made from these scribed reference lines. Impressions were made with monophase addition silicone impression material for each of the specimens. 2% glutaraldehyde was used as a disinfectant. The fabricated dies were measured to the nearest 0.0001 mm. ANOVA and post hoc was carried out using Scheffe multiple comparison test at significance level of 0.05. Type IV resin-impregnated dental stone and copperplated dies approximated the dimensions of the master die. Type IV and V conventional dental stone dies showed greater variation in measurements. Statistically significant differences were observed for type IV resin-impregnated and copper-plated dies in dimension I and III. For dimension II no significant differences were found for dies fabricated from four die materials. A one-way analysis of variance indicated no statistical significant differences among the two groups of dies fabricated from disinfectant treated impressions and those fabricated from nondisinfectant treated impressions. Type IV resin-impregnated dental stone and copper-plated dies are dimensionally more accurate than type IV and V conventional dental stone die materials. No significant linear distortion in the dies fabricated from the disinfected impressions was observed.