A comparison of drying techniques on accuracy of dental stone

Objective: The study compared the accuracy of the drying techniques of working casts in recording the vertical and horizontal dimensional relationship. The working casts are allowed to obtain an adequate hardness for 24 to 48 hours before manipulation, because they are not strong enough after separating them from impression. It is known that conventional and microwave oven drying techniques can save time, but the dimensional accuracy of the material may be affected. Methods: Fortytwo impressions were made of a metal master model with polyvinyl siloxane impression material and poured in Type V dental stone. Specimens were divided into six groups of 7 identical specimens for each. Then, the specimens were dried in a microwave oven for 40 second at 900 W and for 1 minutes at 440 W, in a conventional oven for 30 minutes at 180 °C and for 1 hours at 90 °C, and in air for 12 and 24 hours. Measurements of the stone casts were made in vertical (z axis) and horizontal directions (x and y axes) with 3D measuring device and compared with the master model. Data were analyzed with Mann-Whitney U Test (p<.05). Results: The results revealed that there were no significant differences in the dimensional accuracy in the vertical and horizontal directions of any stone cast after different drying techniques (P>.05). Conclusion: Within the limitations of this study, use of drying techniques not affected the dimensional accuracy of dental stones.