title: Accuracy of the newly formulated vinyl siloxanether elastomeric impression material.
abstract: BACKGROUND
  A newly formulated vinyl siloxanether elastomeric impression material is available, but there is little knowledge of its accuracy in relation to existing materials.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to assess the accuracy of disinfected vinyl siloxanether impressions and compare the accuracy to a common vinyl polysiloxane and a polyether impression system.
  
  
  METHODS
  Impressions were made from a modified dentoform master model containing a simulated crown preparation. Dimensional changes (mm) between the master model and working casts (type IV gypsum) were assessed. The following were evaluated: vinyl polysiloxane in a 1-step, dual-viscosity technique (VPS Dual), polyether as monophase material (PE Mono), and vinyl siloxanether in a 1-step, dual-viscosity (VSE Dual), and monophase technique (VSE Mono). Measurements of the master model and working casts, including anteroposterior (AP) and cross-arch (XA) dimensions, were made with a measuring microscope. The simulated crown preparation was measured in mesiodistal (MDG, MDO), buccolingual (BLG, BLO), and occlusogingival dimensions (OGL, OGB). Disinfection involved immersion for 10 minutes in potassium peroxomonosulfate, sodium benzoate, tartaric acid solution, or no disinfection (control) (n=8). A multivariate GLM statistical approach (MANOVA) was used to analyze the data (alpha=.05). Pearson's correlation test was used for related dimensions.
  
  
  RESULTS
  The AP and XA dimensions of working casts were larger than the master for the disinfected condition and control. Whether disinfected or not, the working dies were shorter in height (OGB, OGL), larger in the buccolingual dimension (BLO, BLG), somewhat larger in the MDO dimension, and somewhat smaller in the MDG dimension compared to the prepared tooth of the master model, resulting in an irregular or oval profile. There were significant differences among the impression systems for each dimension except AP. Differences between the disinfected and nondisinfected conditions were significant (P=.03) with respect to dimensions of the gypsum working cast, but not for dimensions of the working die (P=.97). In general, differences relative to the master were small and of minor clinical significance considering marginal gaps of crowns smaller than 150-100 mum are considered clinically acceptable.
  
  
  CONCLUSIONS
  VSE monophase impressions and VSE dual-viscosity impressions demonstrated acceptable accuracy for clinical use with immersion disinfection, since the results for VSE were comparable to the results for PE and VPS materials, and the differences as compared to the master model were small.
authors.affiliation: University Hospital Heidelberg, 69120 Heidelberg, Germany. thomas.stober@med.uni-heidelberg.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Stober
authors.forename: Glen H
authors.initials: GH
authors.lastname: Johnson
authors.forename: Marc
authors.initials: M
authors.lastname: Schmitter
mesh_terms: D003442:Crowns; D003760:Dental Impression Materials; D004203:Disinfection; D006801:Humans; D016014:Linear Models; D008422:Materials Testing; D003765:Models, Dental; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D014783:Viscosity
chemical_list: D003760:Dental Impression Materials