title: Digital versus conventional implant impressions for edentulous patients: accuracy outcomes.
abstract: OBJECTIVE
  To compare the accuracy of digital and conventional impression techniques for completely edentulous patients and to determine the effect of different variables on the accuracy outcomes.
  
  
  METHODS
  A stone cast of an edentulous mandible with five implants was fabricated to serve as master cast (control) for both implant- and abutment-level impressions. Digital impressions (n = 10) were taken with an intraoral optical scanner (TRIOS, 3shape, Denmark) after connecting polymer scan bodies. For the conventional polyether impressions of the master cast, a splinted and a non-splinted technique were used for implant-level and abutment-level impressions (4 cast groups, n = 10 each). Master casts and conventional impression casts were digitized with an extraoral high-resolution scanner (IScan D103i, Imetric, Courgenay, Switzerland) to obtain digital volumes. Standard tessellation language (STL) datasets from the five groups of digital and conventional impressions were superimposed with the STL dataset from the master cast to assess the 3D (global) deviations. To compare the master cast with digital and conventional impressions at the implant level, analysis of variance (ANOVA) and Scheffe's post hoc test was used, while Wilcoxon's rank-sum test was used for testing the difference between abutment-level conventional impressions.
  
  
  RESULTS
  Significant 3D deviations (P < 0.001) were found between Group II (non-splinted, implant level) and control. No significant differences were found between Groups I (splinted, implant level), III (digital, implant level), IV (splinted, abutment level), and V (non-splinted, abutment level) compared with the control. Implant angulation up to 15° did not affect the 3D accuracy of implant impressions (P > 0.001).
  
  
  CONCLUSIONS
  Digital implant impressions are as accurate as conventional implant impressions. The splinted, implant-level impression technique is more accurate than the non-splinted one for completely edentulous patients, whereas there was no difference in the accuracy at the abutment level. The implant angulation up to 15° did not affect the accuracy of implant impressions.
authors: Division of Postgraduate Prosthodontics, Tufts University School of Dental Medicine, Boston, MA, USA.|Department of Prosthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
authors: Panos
authors: P
authors: Papaspyridakos
authors: Division of Regenerative and Implant Sciences, Harvard School of Dental Medicine, Boston, MA, USA.
authors: German O
authors: GO
authors: Gallucci
authors: Department of Dentistry, Chi Mei Medical Center, Tainan, Taiwan.
authors: Chun-Jung
authors: CJ
authors: Chen
authors: Layerwise, Leuven, Belgium.
authors: Stijn
authors: S
authors: Hanssen
authors: Prosthetics Section, Department of Oral health Sciences, Catholic University of Leuven, Leuven, Belgium.
authors: Ignace
authors: I
authors: Naert
authors: Prosthetics Section, Department of Oral health Sciences, Catholic University of Leuven, Leuven, Belgium.
authors: Bart
authors: B
authors: Vandenberghe
mesh_terms: D017076:Computer-Aided Design; D015921:Dental Implants; D003760:Dental Impression Materials; D003761:Dental Impression Technique; D006801:Humans; D003765:Models, Dental; D009066:Mouth, Edentulous
chemical_list: D015921:Dental Implants; D003760:Dental Impression Materials
keywords: accuracy; dental implants; digital impressions; edentulous; implant impressions; impression techniques