title: Selected characteristics of a new polyvinyl siloxane impression material--a randomized clinical trial.
abstract: OBJECTIVE
  This study evaluated the ability of a new polyvinyl siloxane impression material (Affinis, Coltène/Whaledent, material A) to obtain final impressions free of bubbles and voids for indirect fixed cuspal-coverage restorations. The results were compared to a control polyvinyl siloxane impression material (material B). Both materials were handled by inexperienced clinicians (undergraduate dental students) in student clinics.
  
  
  METHODS
  One-hundred and thirty patients who were treated in the Louisiana State University School of Dentistry Junior Student Clinic for indirect fixed cuspal-coverage restorations and who met the inclusion criteria were randomly assigned to either one of two treatment groups, group A (n = 65) or group B (n = 65). Two calibrated examiners evaluated the first impression of prepared posterior teeth at a magnification of 10x for acceptability (no voids or bubbles). Position of tooth, type of preparation, preparation finish line (Class I-V), and gingival bleeding scores were recorded. All statistical tests were performed with the level of significance set at .05.
  
  
  RESULTS
  The Fisher-Freeman-Halton test did not reveal significant associations between material and gingival bleeding score (P = .492). Significant differences in the location of the preparation finish line between materials were observed (P = .0096); material A was more frequently used in cases where the preparation finish line was located at least 2 mm subgingivally. Logistic regression was used to assess the effect of the material on the success of the impression (acceptable/ unacceptable). Material was highly significant in the logistic model (P < .001) with an odds in favor of an acceptable impression being eight times higher with material A than with material B (odds ratio = 8.00; 95% confidence index for odds ratio: 2.832, 22.601). The 60/65 (92.3%) impressions made with material A and 39/65 (60%) impressions made with material B were rated "acceptable."
  
  
  CONCLUSIONS
  The new polyvinyl siloxane impression material provided a significantly higher proportion of impressions free of bubbles and voids than the control polyvinyl siloxane material.
authors.affiliation: Department of Prosthodontics, Louisiana State University Health Sciences Center School of Dentistry, New Orleans, USA. MBlatz@lsuhsc.edu
authors.forename: Markus B
authors.initials: MB
authors.lastname: Blatz
authors.forename: Avishai
authors.initials: A
authors.lastname: Sadan
authors.forename: John O
authors.initials: JO
authors.lastname: Burgess
authors.forename: Donald
authors.initials: D
authors.lastname: Mercante
authors.forename: Stefan
authors.initials: S
authors.lastname: Hoist
mesh_terms: D016009:Chi-Square Distribution; D003442:Crowns; D003760:Dental Impression Materials; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D011145:Polyvinyls; D016062:Porosity; D011336:Probability; D018401:Sample Size; D012833:Siloxanes
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane