title: Evaluation of impression accuracy for osseointegrated implant supported superstructures.
abstract: BACKGROUND
  An often-debated issue still exists concerning implant impression techniques, whether to splint impression copings. Different configurations are available for these copings for a variety of manufacturers' implant systems.
  
  
  OBJECTIVE
  This study evaluated and compared 4 impression techniques in terms of their dimensional accuracy to reproduce implant positions on working casts.
  
  
  METHODS
  A master model was designed to simulate a clinical situation. Impressions were made using 4 techniques: (1) tapered impression copings not splinted; (2) squared impression copings not splinted; (3) squared impression copings splinted with autopolymerizing acrylic resin; and (4) squared impression copings with a lateral extension on one side not splinted. Reference points machined onto the master model and onto special healing abutments were compared after abutments were transferred to casts using the 4 techniques. Measurements were made using a Reflex microscope, capable of recording in the x-, y-, and z-dimensions.
  
  
  RESULTS
  The dimensional accuracy was high and, although statistically significant (P =.022; power > 80%), a maximum distortion difference of only 0.31% was registered.
  
  
  CONCLUSIONS
  The dimensional accuracy of all the techniques was exceptional and the observed differences can be regarded as clinically negligible.
authors.affiliation: Faculty of Dentistry, University of Pretoria, Pretoria, South Africa.
authors.forename: D
authors.initials: D
authors.lastname: Herbst
authors.forename: J C
authors.initials: JC
authors.lastname: Nel
authors.forename: C H
authors.initials: CH
authors.lastname: Driessen
authors.forename: P J
authors.initials: PJ
authors.lastname: Becker
mesh_terms: D000704:Analysis of Variance; D003198:Computer Simulation; D000044:Dental Abutments; D003761:Dental Impression Technique; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D006801:Humans; D003765:Models, Dental; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric