title: Comparison of space analysis performed on plaster vs. digital dental casts applying Tanaka and Johnston's equation.
abstract: OBJECTIVE
  The purpose of this study was to compare dental size measurements, their reproducibility and the application of Tanaka and Johnston regression equation in predicting the size of canines and premolars on plaster and digital dental casts.
  
  
  METHODS
  Thirty plaster casts were scanned and digitized. Mesiodistal measurements of the teeth were then performed with a digital caliper on the plaster and digital casts using O3d software system (Widialabs©).The sum of the sizes of the lower incisors was used to obtain predictive values of the sizes of the premolars and canines using the regression equation, and these values were compared with the actual sizes of the teeth. The data were statistically analyzed by applying to the results Pearson's correlation test, Dahlberg's formula, paired t-test and analysis of variance (p < 0.05).
  
  
  RESULTS
  Excellent intraexaminer agreement was observed in the measurements performed on both dental casts. No random error was present in the measurements obtained with the caliper and systematic error (bias) was more frequent in the digital casts. Space prediction obtained by applying the regression equation was greater than the sum of the canines and premolars on the plaster and digital casts.
  
  
  CONCLUSIONS
  Despite an adequate reproducibility of the measurements performed on both casts, most measurements on the digital casts were higher than those on the plaster casts. The predicted space was overestimated in both models and significantly higher in the digital casts.
authors.affiliation: Araraquara Dental School, São Paulo State University.
authors.forename: Júlia Olien
authors.initials: JO
authors.lastname: Sanches
authors.forename: Lourdes Aparecida Martins
authors.initials: LA
authors.lastname: dos Santos-Pinto
authors.forename: Ary
authors.initials: A
authors.lastname: dos Santos-Pinto
authors.forename: Betina
authors.initials: B
authors.lastname: Grehs
authors.forename: Fabiano
authors.initials: F
authors.lastname: Jeremias
mesh_terms: D001641:Bicuspid / Q000033:anatomy & histology*; D003481:Cuspid / Q000033:anatomy & histology*; D003735:Dental Casting Technique; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D015588:Observer Variation; D012044:Regression Analysis; D015203:Reproducibility of Results; D012984:Software
keywords: Dental casts; Test reproducibility; Three-dimensional image