title: Diagnostic accuracy of impression-free digital models.
abstract: BACKGROUND
  Impression-free techniques might eliminate the potential shortcomings of digital dental models. Chairside scanners offer the advantage of obtaining digital dental models directly from the patient without the need for dental impressions. The aim of this study was to evaluate the accuracy of 3-dimensional digital models acquired from a chairside intraoral scanner compared with both manual and cone-beam computed tomography measurements of the same dental anatomy.
  
  
  METHODS
  The study sample comprised 60 dry skulls. Each skull had the maxillary and mandibular arches scanned with a Cadent iTero scanner (Align Technology, San Jose, Calif) and had a cone-beam computed tomography scan taken with a CS 9300 unit (Carestream Health, Atlanta, Ga). Linear measurements in all 3 dimensions of the space in each dental arch together with tooth-size arch-length analysis for both the maxillary and mandibular arches were carried out manually on the dry skulls with calipers and digitally on the scanned 3-dimensional models and cone-beam computed tomography images. Intraclass correlation (ICC) analysis was performed for all variables tested in the study groups, with the manual measurements on the dry skulls as the gold standard. The Bland-Altman analysis was also applied to the data to graphically display the agreement of the diagnostic measurements obtained from these methods.
  
  
  RESULTS
  Measurements from the iTero models demonstrated near-perfect agreement (ICC, 0.91-0.99) with the caliper measurements. Cone-beam computed tomography measurements had moderate to high levels of agreement (ICC, 0.65-0.99) compared with the caliper measurements.
  
  
  CONCLUSIONS
  Direct digital acquisition of the dental arches with a chairside scanner provided almost 1-to-1 diagnostic information of the investigated anatomy and was superior to the cone-beam computed tomography measurements.
authors.affiliation: Assistant professor, Department of Orthodontics, School of Dentistry, University of Texas Health Science Center at Houston, Tex. Electronic address: Sercan.Akyalcin@uth.tmc.edu.
authors.forename: Sercan
authors.initials: S
authors.lastname: Akyalcin
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Cozad
authors.forename: Jeryl D
authors.initials: JD
authors.lastname: English
authors.forename: Clark D
authors.initials: CD
authors.lastname: Colville
authors.forename: Stephen
authors.initials: S
authors.lastname: Laman
mesh_terms: D002508:Cephalometry / Q000295:instrumentation*; D054893:Cone-Beam Computed Tomography; D003724:Dental Arch / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D007834:Lasers; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008437:Maxilla / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D003765:Models, Dental; D009970:Orthodontics / Q000295:instrumentation; D015203:Reproducibility of Results; D012886:Skull / Q000033:anatomy & histology