title: Effect of tissue conditioners on the dynamic viscoelastic properties of a heat-polymerized denture base.
abstract: BACKGROUND
  Little is known about the influence of tissue conditioners on physical property alteration of denture base resins.
  
  
  OBJECTIVE
  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.
  
  
  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 degrees C with an automatic viscoelastometer. Tensile storage modulus (E'), tensile loss modulus (E"), and loss tangent (tan delta) 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 delta 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 delta than the control. However, only Hydro-Cast and SR-Ivoseal significantly decreased E', and only Hydro-Cast raised tan delta 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 delta of acrylic resin specimens 1.0-mm thick.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan. hmurata@hiroshima-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Murata
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Toki
authors.forename: Guang
authors.initials: G
authors.lastname: Hong
authors.forename: Taizo
authors.initials: T
authors.lastname: Hamada
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000704:Analysis of Variance; D003799:Dental Stress Analysis; D003819:Denture Bases; D003779:Denture Design; D003822:Denture Liners; D004548:Elasticity; D006358:Hot Temperature; D007101:Immersion; D008422:Materials Testing; D008768:Methylmethacrylates / Q000737:chemistry; D010795:Phthalic Acids / Q000737:chemistry; D010968:Plasticizers / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D013718:Tensile Strength; D014016:Tissue Conditioning, Dental; D014783:Viscosity
chemical_list: D000180:Acrylic Resins; D008768:Methylmethacrylates; D010795:Phthalic Acids; D010968:Plasticizers; D011108:Polymers; C069456:Hydro-Cast dental tissue conditioner; C043685:Coe Comfort; C009931:poly(ethylmethacrylate)