Effect of the second wash in one- and two-step impression technique on marginal adaptation

AbstractIntroduction: The success of fixed prosthodontics requires a precise registration of the prepared teeth and finishing line, which necessitates finding to simple technique of impression taking so that an acceptable impression with record of details can be achieved. This research was performed to evaluate the effect of the second wash of Speedex impression material in one- and two-step impression technique on marginal adaptation of the crown. Materials and methods: In this in vitro study a laboratory model with two metal dies (similar to the 2nd premolar the 2nd molar) and condensation silicone impression material (Speedex) were used. Impressions were made in four techniques (one-step, one-step with second wash, two-step with 2 mm of space, two-step with a second wash). Each technique was repeated 15 times and 60 impressions were obtained, which were poured with Type IV dental stone. On each die a wax pattern of a three-component bridge was framed and casting was carried out with a metal alloy. The marginal fitness of the frames was viewed and measured under a stereomicroscope at ×100 magnification with a digital micrometer in four areas. The results were analyzed by Tukey test and ANOVA. Results: The least and greatest marginal gaps were observed in the anterior abutment with the two-step technique and the posterior abutment with one-step technique with a second wash (69.56 and 85.59 microns, respectively). The amounts of marginal gaps were clinically acceptable in all the four methods. There were no significant differences between the one-step and two-step techniques (p value = 1) and between one-step technique and two-step technique with a second wash (p value = 0.6). Conclusion: For each four technique the amount of marginal gap was acceptable; therefore, a second wash can be added to the primary wash to achieve more precise impressions with registration of details and finishing line. However, further evaluations are necessary. Key words: Impression material, Impression technique, Marginal adaptation, Tooth