title: Comparison of reconstructed rapid prototyping models produced by 3-dimensional printing and conventional stone models with different degrees of crowding.
abstract: BACKGROUND
  Rapid prototyping models can be reconstructed from stereolithographic digital study model data to produce hard-copy casts. In this study, we aimed to compare agreement and accuracy of measurements made with rapid prototyping and stone models for different degrees of crowding.
  
  
  METHODS
  The Z Printer 450 (3D Systems, Rock Hill, SC) reprinted 10 sets of models for each category of crowding (mild, moderate, and severe) scanned using a structured-light scanner (Maestro 3D, AGE Solutions, Pisa, Italy). Stone and RP models were measured using digital calipers for tooth sizes in the mesiodistal, buccolingual, and crown height planes and for arch dimension measurements. Bland-Altman and paired t test analyses were used to assess agreement and accuracy. Clinical significance was set at ±0.50 mm.
  
  
  RESULTS
  Bland-Altman analysis showed the mean bias of measurements between the models to be within ±0.15 mm (SD, ±0.40 mm), but the 95% limits of agreement exceeded the cutoff point of ±0.50 mm (lower range, -0.81 to -0.41 mm; upper range, 0.34 to 0.76 mm). Paired t tests showed statistically significant differences for all planes in all categories of crowding except for crown height in the moderate crowding group and arch dimensions in the mild and moderate crowding groups.
  
  
  CONCLUSIONS
  The rapid prototyping models were not clinically comparable with conventional stone models regardless of the degree of crowding.
authors.affiliation: Department of Paediatric Dentistry and Orthodontics, and Clinical Craniofacial Dentistry Research Group, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia. Electronic address: wannurazreena@um.edu.my.
authors.forename: Wan Nurazreena
authors.initials: WN
authors.lastname: Wan Hassan
authors.affiliation: Department of Paediatric Dentistry and Orthodontics, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Yusnilawati
authors.initials: Y
authors.lastname: Yusoff
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Noor Azizi
authors.initials: NA
authors.lastname: Mardi
mesh_terms: D006801:Humans; D008310:Malocclusion / Q000473:pathology*; D003765:Models, Dental; D066330:Printing, Three-Dimensional; D012720:Severity of Illness Index