Effects of glow-discharge and surfactant treatments on the wettability of vinyl polysiloxane impression materials

Statement of problem. Although surfactant-modified vinyl polysiloxane (VPS) is described as hydrophilic by manufacturers, interaction with dental gypsum is relatively poor. Purpose. The purpose of this study was to compare and evaluate the wettability of surfactant-modified VPS after different surface treatments. Material and methods. Eighty-four impression-material specimens (20 x 10 x 1 mm) were prepared from 3 different brands of VPS (Aquasil, Panasil Contact Plus, and Accuflex). Four groups (n = 7) of specimens were established according to the surface treatment method used: no treatment, topical application of 2 different surface wettability agents (Silwet Copolymer L-77 or Delar surfactant), or coating with an acrylic acid plasma in a glow-discharge reactor. Plasma treatment specimens were coated with acrylic acid in a glow-discharge system at a radio frequency of 13.56 MHz with 20-W discharge power and 5 minutes of exposure time. Wettability was measured using the contact-angle method. Values were recorded after the drop contacted the surface at 0.6 second, 30.7 seconds, and 210.8 seconds. Contact-angle mean values were compared using 3-way analysis of variance with repeated measures on 1 factor, followed by a post hoc Duncan test (alpha=.05). Results. As the sphericity assumption was not satisfied, the Greenhouse-Geisscr correction was used for contact-angle values. Glow-discharge treatment proved to be effective for increasing the surface energy of the VPS compared to controls at all time points studied (P <.0001). At 0.6 second, Silwet significantly decreased the contact-angle values for Aquasil and for Panasil Contact Plus (P <.0001). Delar treatment, at this time point, significantly increased the contact-angle values of GC (P <.0001) and decreased the contact-angle values of Aquasil (P <.0001). At 30.7 seconds, Silwet significantly increased the wettability of Aquasil and Panasil Contact Plus (P <.0001) but did not significantly increase the wettability of GC. Delar treatment, at 30.7 seconds, increased the contact-angle values of GC (P <.0001), whereas contact-angle values of Aquasil significantly decreased (P <.0001). At 210.8 seconds, all surface-modification methods used were effective in increasing the wettability of VPS tested over untreated controls (P <.0001). Conclusion. Wettability of VPS-based impression materials can be increased by coating the surface with acrylic acid in a glow-discharge reactor. The change in wettability achieved by the application of topical surfactants resulted in variations among surfactant-VPS combinations.