title: Accuracy of three polyvinyl siloxane putty-wash impression techniques.
abstract: BACKGROUND
  There is much discussion in the dental literature concerning the effect of the impression technique on the accuracy of cast restorations.
  
  
  OBJECTIVE
  This study assessed the accuracy of 3 putty-wash impression techniques using the same impression material (polyvinyl siloxane) in a laboratory model.
  
  
  METHODS
  The 3 putty-wash impression techniques used were (1) 1-step (putty and wash impression materials used simultaneously); (2) 2-step with 2-mm relief (putty first as a preliminary impression to create 2-mm wash space with prefabricated copings. In the second step, the wash stage was carried out); and (3) 2-step technique with a polyethylene spacer (plastic spacer used with the putty impression first and then the wash stage). For each technique, 15 impressions were made of a stainless steel master model that contained 3 complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring 6 dimensions (intraabutment and interabutment) on stone dies poured from impressions of the master model.
  
  
  RESULTS
  One-way analysis of variance showed statistically significant differences among the 3 putty-wash impression techniques, for all intraabutment and interabutment measurements (P <.001). Overall discrepancies of the 2-step technique with 2-mm relief putty-wash impression technique were significantly smaller than that in the 1-step and polyethylene putty-wash impression techniques.
  
  
  CONCLUSIONS
  The polyvinyl siloxane 2-step, 2-mm, relief putty-wash impression technique was the most accurate for fabricating stone dies.
authors.affiliation: The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel. nissandr@post.tau.ac.il
authors.forename: J
authors.initials: J
authors.lastname: Nissan
authors.forename: B Z
authors.initials: BZ
authors.lastname: Laufer
authors.forename: T
authors.initials: T
authors.lastname: Brosh
authors.forename: D
authors.initials: D
authors.lastname: Assif
mesh_terms: D000704:Analysis of Variance; D000044:Dental Abutments; D003760:Dental Impression Materials; D003761:Dental Impression Technique; D003830:Denture, Partial, Fixed; D008422:Materials Testing; D003765:Models, Dental; D011145:Polyvinyls; D015203:Reproducibility of Results; D012833:Siloxanes
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane