title: Digital versus plaster study models: how accurate and reproducible are they?
abstract: OBJECTIVE
  To compare measurements of occlusal relationships and arch dimensions taken from digital study models with those taken from plaster models.
  
  
  METHODS
  Laboratory study
  
  
  METHODS
  The Orthodontic Department, Kettering General Hospital, Kettering, UK Methods and materials: One hundred and twelve sets of study models with a range of malocclusions and various degrees of crowding were selected. Occlusal features were measured manually with digital callipers on the plaster models. The same measurements were performed on digital images of the study models. Each method was carried out twice in order to check for intra-operator variability. The repeatability and reproducibility of the methods was assessed.
  
  
  RESULTS
  Statistically significant differences between the two methods were found. In 8 of the 16 occlusal features measured, the plaster measurements were more repeatable. However, those differences were not of sufficient magnitude to have clinical relevance. In addition there were statistically significant systematic differences for 12 of the 16 occlusal features, with the plaster measurements being greater for 11 of these, indicating the digital model scans were not a true 11 representation of the plaster models.
  
  
  CONCLUSIONS
  The repeatability of digital models compared with plaster models is satisfactory for clinical applications, although this study demonstrated some systematic differences. Digital study models can therefore be considered for use as an adjunct to clinical assessment of the occlusion, but as yet may not supersede current methods for scientific purposes.
authors.affiliation: Eastman Dental Institute and Kettering General Hospital, London, UK. neilufar.abizadeh@gmail.com
authors.forename: Neilufar
authors.initials: N
authors.lastname: Abizadeh
authors.forename: David R
authors.initials: DR
authors.lastname: Moles
authors.forename: Julian
authors.initials: J
authors.lastname: O'Neill
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Noar
mesh_terms: D002133:Calcium Sulfate; D002508:Cephalometry / Q000379:methods*; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D003766:Dental Occlusion; D061827:Dimensional Measurement Accuracy; D049691:History, Medieval; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods; D008310:Malocclusion / Q000175:diagnosis; D003765:Models, Dental; D015588:Observer Variation; D009811:Odontometry / Q000379:methods; D015203:Reproducibility of Results
chemical_list: D002133:Calcium Sulfate