title: An in vitro comparison of 5 techniques for impressing dowel space preparations.
abstract: OBJECTIVE
  This in vitro study compared 5 different dowel space impression techniques using polyvinyl siloxane impression material to determine which method produced fewer voids in the dowel space impression.
  
  
  METHODS
  Five techniques were used to make impressions of a prepared dowel space in a simulated endodontically treated tooth. Technique I used a 25-gauge anesthetic needle to act as a vent at the apex of the preparation to reduce voids produced during the expression of light body impression material. The anesthetic needle was removed after the impression material was injected, and an impression post was then inserted to the depth of the preparation. Twenty impressions made using this technique were compared with other techniques that used the vent without a post, no vent with a post, no vent without a post, and a lentulo spiral with a post (Techniques II through V, respectively). The percentage of impressions with voids from each group was compared to determine which technique consistently produced a void-free impression of the complete preparation length. If voids were observed in the impression, the specimen was considered inadequate.
  
  
  RESULTS
  The percents of void-free impressions using Techniques I through V were 100%, 70%, 40%, 60%, and 20%, respectively.
  
  
  CONCLUSIONS
  Using a 25-gauge needle as a vent while expressing impression material into the dowel space followed by placing the impression post consistently produced void-free dowel space impressions.
authors.affiliation: School of Dentistry, Room 4374, University Park, University of Southern California, Los Angeles, CA 90089-0641, USA. wchee@hsc.usc.edu
authors.forename: W W
authors.initials: WW
authors.lastname: Chee
authors.forename: G C
authors.initials: GC
authors.lastname: Cho
authors.forename: R
authors.initials: R
authors.lastname: Marzola
mesh_terms: D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique / Q000295:instrumentation; D003786:Dental Pulp Cavity; D006801:Humans; D008422:Materials Testing; D008953:Models, Anatomic; D009339:Needles; D011145:Polyvinyls / Q000737:chemistry; D011176:Post and Core Technique; D012390:Root Canal Therapy; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane