title: The effect of one-step vs. two-step impression techniques on long-term accuracy and dimensional stability when the finish line is within the gingival sulcular area.
abstract: OBJECTIVE
  To evaluate the effect of two putty-wash impression techniques on the long-term accuracy and dimensional stability of poly(vinyl siloxane) (PVS) in the gingival sulcus area.
  
  
  METHODS
  Impressions were taken from a master cast to simulate molar crown preparation. A space around the abutment served as the gingival sulcus. Fifteen impressions using the one- and two-step impression techniques were taken using Express Regular, Express Fast, and President impression materials with custom trays. Using a Toolmaker's microscope, the long (LD) and short distances (SD) of the abutment and the planar distance between two parallel lines (PL) at the circumference of the cast were taken at 0.5, 2, 24, 48, 72, 96, 120, and 144 hours after mixing. ANOVA was performed, with the discrepancy between the distances of the impressions and the master cast as the dependent variable.
  
  
  RESULTS
  The differences when different materials and impression techniques were used were significant (p < 0.001) for LD, SD, and PL, as was the interaction between the material, time, and technique (p < 0.001). SD discrepancies were higher than those of LD for all materials and times. The two-step impression technique was more accurate, with smaller discrepancies than the one-step impression technique. For all materials, the PL discrepancy was deemed acceptable (less than 0.5%) for all tested times. President had higher discrepancies than the other materials.
  
  
  CONCLUSIONS
  When using the two-step putty-wash impression technique, pouring of the impressions may be postponed up to 30 hours; however, when using the one-step impression technique, pouring should be performed within 2 hours.
authors.affiliation: Department of Oral Rehabilitation, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Shifra
authors.initials: S
authors.lastname: Levartovsky
authors.forename: Maayan
authors.initials: M
authors.lastname: Zalis
authors.forename: Raphael
authors.initials: R
authors.lastname: Pilo
authors.forename: Noga
authors.initials: N
authors.lastname: Harel
authors.forename: Yehuda
authors.initials: Y
authors.lastname: Ganor
authors.forename: Tamar
authors.initials: T
authors.lastname: Brosh
mesh_terms: D000044:Dental Abutments / Q000592:standards; D003760:Dental Impression Materials / Q000737:chemistry / Q000592:standards*; D003761:Dental Impression Technique / Q000295:instrumentation / Q000592:standards*; D005881:Gingiva / Q000033:anatomy & histology*; D006801:Humans; D008422:Materials Testing; D008963:Molar / Q000033:anatomy & histology; D011145:Polyvinyls / Q000737:chemistry / Q000592:standards*; D012828:Silicones / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry / Q000592:standards*; D013499:Surface Properties; D013997:Time Factors; D019231:Tooth Preparation, Prosthodontic / Q000592:standards
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012828:Silicones; D012833:Siloxanes; C118335:president, silicone impression material; C034183:vinyl polysiloxane
keywords: Impression technique; accuracy; dimensional stability; gingival sulcular area; poly(vinyl siloxane)