title: A new method for the evaluation of the accuracy of full-arch digital impressions in vitro.
abstract: OBJECTIVE
  Introducing a new approach to evaluate the accuracy of digital impression methods for full-arch scans, avoiding "best-fit alignment."
  
  
  METHODS
  A lower jaw model with a straight metal bar between the second molars of both quadrants was directly digitized using an intraoral scanner (True Definition, TRD, n = 12) and indirectly digitized (D810, CON, n = 12) after impression and plaster cast. A dataset of the bar from a coordinate measuring machine served as reference (REF). Datasets obtained from test groups were analyzed using inspection software to determine the aberration of the bar length, the linear shift (in X-, Y-, Z-axis) and the angle deviation (α overall, α coronal, α horizontal) caused by the digitalization method. Mann-Whitney U and unpaired two-sample Student's t test were implemented to detect differences. The level of significance was set at 5 %.
  
  
  RESULTS
  Concerning the bar length, no significant differences were found between groups. In view of the linear shift, CON showed significantly higher values than TRD in Y-axis (p = 0.003) and in Z-axis (p = 0.040). Regarding the angle measurement, TRD showed significant smaller values than CON for α overall (p = 0.006) and for α coronal (p = 0.005).
  
  
  CONCLUSIONS
  This in vitro study shows that intraoral scanning systems seem to show the same or even higher accuracy than the conventional impression with subsequent indirect digitalization.
  
  
  CONCLUSIONS
  Intraoral scanners have proven excellent accuracy for single teeth or small spans. However, insufficient data is available about their accuracy for full-arch scans. The presented new approach seems to be suitable to precisely analyze differences in the accuracy of different digitalization methods without using best-fit alignment.
authors.affiliation: Department of Prosthodontics, Dental School of the Ludwig-Maximilians University Munich, Goethestraße 70, 80336, Munich, Germany. jan_frederik.gueth@med.uni-muenchen.de.
authors.forename: Jan-Frederik
authors.initials: JF
authors.lastname: Güth
authors.affiliation: Department of Prosthodontics, Dental School of the Ludwig-Maximilians University Munich, Goethestraße 70, 80336, Munich, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Edelhoff
authors.affiliation: Department of Prosthodontics, Dental School of the Ludwig-Maximilians University Munich, Goethestraße 70, 80336, Munich, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Schweiger
authors.affiliation: Department of Prosthodontics, Dental School of the Ludwig-Maximilians University Munich, Goethestraße 70, 80336, Munich, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Keul
mesh_terms: D017076:Computer-Aided Design; D003724:Dental Arch; D003760:Dental Impression Materials; D003761:Dental Impression Technique; D006801:Humans; D021621:Imaging, Three-Dimensional; D066298:In Vitro Techniques; D003765:Models, Dental; D015203:Reproducibility of Results
chemical_list: D003760:Dental Impression Materials
keywords: Accuracy; CAD/CAM; Digital impression; Digital workflow; Full-arch scan; Intraoral scanner