title: Influence of impression material and time on the 3-dimensional accuracy of implant impressions.
abstract: OBJECTIVE
  To investigate, in vitro, the effect of time on the 3-dimensional accuracy of open-tray implant impression copings made of polyvinyl siloxane and polyether impression materials.
  
  
  METHODS
  Reference models with 4 internal connection implants were fabricated. Four sets of 71 direct impressions were made with square impression copings using an open-tray technique. One set of impressions was made with polyether material (material A) and each of 3 polyvinyl siloxane materials (materials B, C, and D). Three-dimensional changes in spatial orientation of the implant analogs were measured over 48 hours using an optical measurement device. Deviation values were summed over 4 points and averaged per impression. Global differences were tested with a nonparametric Kruskal-Wallis test followed by pairwise comparisons using the Mann-Whitney U test.
  
  
  RESULTS
  The mean dimensional accuracy of implant impressions significantly differed over time (P < .001). Materials A and B were found to produce comparable results, For materials C and D there was a significant increase in deviations, with a maximum increase at 2 hours. Deviations for material C were comparable to materials A and B at 48 hours. Baseline values were not maintained by any material.
  
  
  CONCLUSIONS
  Within the limits of this in vitro study, it can be concluded that time cannot be neglected as a factor affecting the accuracy of implant master casts.
authors.affiliation: Department of Prosthodontics, Friedrich Alexander University Erlangen-Nuremberg, Erlangen, Germany. sholst@prothetik-erlangen.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Holst
authors.forename: Markus B
authors.initials: MB
authors.lastname: Blatz
authors.forename: Michael
authors.initials: M
authors.lastname: Bergler
authors.forename: Matthias
authors.initials: M
authors.lastname: Goellner
authors.forename: Manfred
authors.initials: M
authors.lastname: Wichmann
mesh_terms: D015921:Dental Implants; D003760:Dental Impression Materials; D003761:Dental Impression Technique; D017267:Dental Prosthesis Design; D004987:Ethers; D003765:Models, Dental; D011145:Polyvinyls; D012833:Siloxanes; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D015921:Dental Implants; D003760:Dental Impression Materials; D004987:Ethers; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane