Avaliação da alteração dimensional de siliconas de reação por condensação e adição, em função dos modelos de gesso obtidos em diferentes tempos de armazenagem dos seus moldes

Abstract

Two condensation-type silicones (Speedex and Optosil Comfort/ Xantopren VL Plus) are available commercially as high dimensional stability impression materials that could be kept stable for 7 days, without lost the precision of molds, according to their manufacturers. The purpose of this study was to evaluate the dimensional change of three commercial condensation-type silicone (Speedex-Coltène, Optosil Comfort/Xantopren VL Plus -Kulzer and Coltoflax/Coltex-Coltène) and one addition-type silicone (President-Coltène), as a function of the stone cast made at different storage time of their molds. Metallic replicas CeraOne WP DCA 686-0 WP, Nobel Biocare (batch 23218), were used as master die unitary and parcel and were impressed by putty/wash technique using individual perforated tray. The impressions were stored at room temperature (25 2°C) and 50% relative humidity, and poured with type IV stone Velmix at different times: immediate, 1 hour, 2 hours, 1, 3 and 7 days. Each stone cast were measured in standard position by three examinations using a Digital Micrometer Mitutoyo. Data were subjected to statistical analysis (Kruskal Wallis Test, =0,05, n=5). The average percentage values of the size difference between the metallic replica and the stone casts indicated that all impression materials showed a contraction in direction to the center of the mold, since a reduction was detected in the cast's size with the increase in storage time. It can be concluded that molds of Speedex, Optosil Comfort/Xantopren VL Plus and President could be storage for 7 days, while the casts of Coltoflax/Coltex molds should be poured as soon as possible, within a period of 2 hours, to guarantee their precision.