title: Dimensional accuracy of resultant casts made by a monophase, one-step and two-step, and a novel two-step putty/light-body impression technique: an in vitro study.
abstract: BACKGROUND
  Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to compare the dimensional accuracy of a monophase, 1- and 2-step putty/light-body, and a novel 2-step injection impression technique.
  
  
  METHODS
  A stainless steel model with 2 abutment preparations was fabricated, and impressions were made 15 times with each technique. All impressions were made with an addition-reaction silicone impression material (Aquasil) and a stock perforated metal tray. The monophase impressions were made with regular body material. The 1-step putty/light-body impressions were made with simultaneous use of putty and light-body materials. The 2-step putty/light-body impressions were made with 2-mm-thick resin-prefabricated copings. The 2-step injection impressions were made with simultaneous use of putty and light-body materials. In this injection technique, after removing the preliminary impression, a hole was made through the polymerized material at each abutment edge, to coincide with holes present in the stock trays. Extra-light-body material was then added to the preliminary impression and further injected through the hole after reinsertion of the preliminary impression on the stainless steel model. The accuracy of the 4 different impression techniques was assessed by measuring 3 dimensions (intra- and interabutment) (5-mum accuracy) on stone casts poured from the impressions of the stainless steel model. The data were analyzed by 1-way ANOVA and Student-Newman-Keuls test (alpha=.05).
  
  
  RESULTS
  The stone dies obtained with all the techniques had significantly larger dimensions as compared to those of the stainless steel model (P<.01). The order for highest to lowest deviation from the stainless steel model was: monophase, 1-step putty/light body, 2-step putty/light body, and 2-step injection. Significant differences among all of the groups for both absolute dimensions of the stone dies, and their percent deviations from the stainless steel model (P<.01), were noted.
  
  
  CONCLUSIONS
  The 2-step putty/light-body and 2-step injection techniques were the most dimensionally accurate impression methods in terms of resultant casts.
authors.affiliation: Prosthetic Dentistry, Department of Oral Sciences, University G. D'Annunzio, Chieti, Italy. s.caputi@unich.it
authors.forename: Sergio
authors.initials: S
authors.lastname: Caputi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Varvara
mesh_terms: D002133:Calcium Sulfate / Q000737:chemistry; D000044:Dental Abutments; D003760:Dental Impression Materials / Q000737:chemistry* / Q000145:classification; D003761:Dental Impression Technique / Q000295:instrumentation; D003764:Dental Materials / Q000737:chemistry; D020724:Elastomers / Q000737:chemistry; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D008768:Methylmethacrylates / Q000737:chemistry; D003765:Models, Dental; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013193:Stainless Steel; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003760:Dental Impression Materials; D003764:Dental Materials; D020724:Elastomers; D008768:Methylmethacrylates; D011145:Polyvinyls; D012833:Siloxanes; C480691:aquasil; D013193:Stainless Steel; C034578:Duralay; D002133:Calcium Sulfate