Reliability of multiple pour between two classes of polyvinyl siloxane impression materials: A preliminary stereomicroscopic study

Objective: To evaluate the accuracy and dimensional stability of casts made from regular set alginate alternative (AA) and monophase additional silicone (MAS) impression materials following multiple pours. Materials and Methods: A hard typodont master cast with index holes was used. A total of 20 impressions were made using a modified perforated metal tray with 10 impressions of each material. Each impression was poured four times with type IV die stone with a total of 80 stone casts (40 for each material). The horizontal anterior–posterior (HAP), horizontal cross-arch (HCA), and vertical distances were measured in the recovered stone casts using a stereomicroscope with an accuracy of 0.001 mm. The obtained data were statistically analyzed using two-way analysis of variance and Tukey's HSD post hoc test (P < 0.05). Results: The dimensions on the typodont master cast and stone casts were significantly different (P < 0.001), except for the first pour from MAS (P > 0.05). There was a statistically significant difference in the dimensions of the stone casts made from the AA and MAS impression materials among the four pour groups (P < 0.001), with exception of MAS-based casts between first pour and second pour groups at HAP and HCA dimensions. Pairwise comparisons showed statistically significant difference between the two impression materials at all measurement locations, with only one exception of HAP measurements for second-poured casts. Conclusion: A clinically acceptable casts can be made by pouring AA and MAS impressions twice. In addition, the third and fourth pours were accurate in the AA group when compared to MAS group. Clinical Significance: According the knowledge of the authors, this study is the first to evaluate the predictability of re-pouring alginate alternative impression material and compare to a standard polyvinyl siloxane impression material such as monophase. Therefore, the statement of clinical significance in the abstract will help the dentists to realize the potential uses for alginate alternative impression material and recommendations of this study.