Effect of metallic flask closure and investment materials on the stability of the denture base resin

Abstract

AbstractThis study evaluated the dimensional stability of the poly‐methylmethacrylate (PMMA) denture bases under the effect of different metallic flask closure techniques (FCT) and investment materials (IM). Sixty stone cast maxillary‐wax base plate sets were randomly assigned to six groups (n = 10) for the following treatments: 1 and 4—stone or silicone investments and flask closure with clamp; 2 and 5—stone or silicone investments and flask closure with RS system; 3 and 6—stone or silicone investments and flask closure with screws. PMMA denture bases were polymerized in a water bath at 74°C for 9 h. PMMA base‐stone cast sets were sectioned at regions (R) of the canines, first molars, and posterior palatal zone. Gap discrepancies were measured at five points: right and left ridge crests, palatal midline, and right and left marginal limits of the flanges. An optical micrometer with accuracy of 0.0005 mm was used for measurement purposes. Data were submitted to ANOVA and Tukey's test (α = 0.05). Silicone showed an adaptation mean (0.177 mm) significantly different when compared with stone (0.207 mm). The RS system presented a statistically different adaptation mean (0.166 mm) in relation to the traditional clamp (0.200 mm) and flask with screws (0.211 mm). Adaptation values for the regions of the canines (0.141 mm), first molars (0.185 mm), and posterior palatal (0.250 mm) were statistically different. For all flask closure techniques, better adaptation was shown with the RS system and silicone investment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010