Dimensional Accuracy of Stone Casts Obtained with Multiple Pours into the Same Mold

Aim. The aim of the present study was to compare the dimensional accuracy of stone casts obtained with vinyl polysiloxane molds through the double-impression technique with three pours into the same mold. Methods. A stainless steel master model was constructed simulating a three-unit fixed prosthesis. Twelve impressions were taken of this master model with addition silicone, using the double-impression technique. Three pours of type IV gypsum were then made into each mold, thus producing 36 casts. The pours were made 1 hour, 6 hours and 24 hours after the impression procedure. Next, intra- and interabutment measurements were made in a coordinate measuring machine. Results. Comparative analysis of the dimensional accuracy of stone casts resulting from multiple pours was not statistically significant in pours first and second ( ). These values, however, were statistically significant at third pour in the height in abutment 1 and upper distance interabutment. Conclusion. The wait time (1 hour, and 6 hours) observed before pouring the stone into the same molds did not cause significant dimensional accuracy of the casts. 1. Introduction In order to construct a fixed prosthesis, a stone die must be made by cutting the stone cast that was obtained through an impression technique. Separated from the cast, this die enables improved marginal adaptation of the prosthetic crown that will be constructed on it. Although current techniques for making removable stone dies have developed and become increasingly more accurate, the cutting out of a stone die results in significant dimensional change in the distances between abutments [1]. In this scenario, producing more than one cast from the same mold may be an option for preserving the marginal adaptation of prostheses—a result for which obtaining stone dies is required—while at the same time, preserving the dimensional accuracy of the distances between the prosthetic abutments [2]. A deficiency to making impressions in fixed prosthodontics is failure to follow basic principles inherent to the manipulation of impression materials. Stock trays are used extensively, and the importance of control of bulk is ignored. Putty/wash materials also are used extensively, usually in an inappropriate manner, resulting in impressions with less than optimal accuracy [3]. Since the most costly item of any oral rehabilitation treatment is the clinical time of the dental professional, the possibility of obtaining several casts from the same mold without changing their characteristics and dimensions could contribute to reducing the