title: Effect of multiple use of impression copings on the accuracy of implant transfer.
abstract: OBJECTIVE
  Reuse of metal impression copings may be desirable for both economic and environmental reasons. When impression copings are reused, it is important to be assured that they are as accurate as new ones. The purpose of the present in vitro study was to assess the effect of multiple use of impression copings on the accuracy of direct and indirect implant transfer techniques.
  
  
  METHODS
  An acrylic resin cast with five internal connection implants was fabricated. Forty medium-consistency polyether impressions of the cast with direct and indirect techniques were made using four sets (five each) of impression copings (square or conical). Impressions were poured with type IV dental stone. Then, the copings were subjected to a cleaning and sterilization process. The process was repeated 10 times with the same copings. Positional accuracy of the implant replica heads in x-, y-, and z-axes and also angular displacement (Δθ) were assessed using a coordinate measuring machine. These measurements were compared with the measurements made on the resin cast (control). Analysis of covariance for repeated measurements was used for the statistical analysis (α =.05).
  
  
  RESULTS
  There were no significant differences among the following measurements: θx, θz, ;Δθ, and θr (P > .05) in both techniques. Only θy for the open tray impression technique was influenced during repeated use of impression copings (P = .02).
  
  
  CONCLUSIONS
  Within the limitations of this study, it could be concluded that impression copings can be successfully used, cleaned and sterilized up to 10 times without compromising the impression accuracy.
authors.affiliation: Dental Research Center, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Marzieh
authors.initials: M
authors.lastname: Alikhasi
authors.forename: Seyed Hossein
authors.initials: SH
authors.lastname: Bassir
authors.forename: Roshanak Baghai
authors.initials: RB
authors.lastname: Naini
mesh_terms: D000180:Acrylic Resins; D000704:Analysis of Variance; D000044:Dental Abutments; D003735:Dental Casting Technique / Q000592:standards*; D015921:Dental Implants; D003760:Dental Impression Materials / Q000592:standards*; D003761:Dental Impression Technique / Q000592:standards*; D003764:Dental Materials; D003772:Dental Pins; D017743:Equipment Reuse / Q000592:standards*; D003765:Models, Dental; D013242:Sterilization / Q000379:methods
chemical_list: D000180:Acrylic Resins; D015921:Dental Implants; D003760:Dental Impression Materials; D003764:Dental Materials