Effect of tissue conditioners on the dynamic viscoelastic properties of a heat-polymerized denture base☆☆☆★★★♢

Abstract 

Statement of Problem. Little is known about the influence of tissue conditioners on physical property alteration of denture base resins. Purpose. This study evaluated the influence of a variety of commercial tissue conditioners on alteration of viscoelastic properties of a heat-polymerized denture base acrylic resin. Material and Methods. Four tissue conditioners and 1 heat-polymerized denture base acrylic resin were used. In one experiment, acrylic resin specimens (1.0-mm thick) were immersed in the liquid component of tissue conditioners for 36 hours. In another experiment, tissue conditioners were applied to acrylic resin specimens (0.5-mm and 1.0-mm thick) in a 2-mm layer; the specimens then were immersed in distilled water for 1 week. Control specimens for both groups had no lining and were immersed in distilled water for 36 hours and 1 week, respectively. Dynamic viscoelastic properties of the acrylic resin specimens were measured at 37°C with an automatic viscoelastometer. Tensile storage modulus (E′), tensile loss modulus (E″), and loss tangent (tan δ) were determined at 1 Hz. These parameters were compared with analysis of variance and the Dunnett test at a predetermined significance level of .05. All statistical comparisons were made with reference to the control group and not to each other. Results. Only the liquid of Hydro-Cast significantly reduced E′ and increased tan δ of the acrylic resin (P<.05). Acrylic resin specimens 0.5-mm thick and lined with tissue conditioners tended to have lower E′ and higher tan δ than the control. However, only Hydro-Cast and SR-Ivoseal significantly decreased E′, and only Hydro-Cast raised tan δ of the acrylic resin (P<.05). No significant difference was found among the E″ values. The tissue conditioners did not affect E′, E″, or tan δ of acrylic resin specimens 1.0-mm thick. Conclusion. Within the limitations of this study, some tissue conditioners significantly plasticized the denture base acrylic resin 0.5-mm thick. However, when the acrylic resin was 1.0-mm thick, no plasticization by the tissue conditioners was noted. (J Prosthet Dent 2002;88:409-14.)