title: Three-dimensional computer-assisted study model analysis of long-term oral-appliance wear. Part 1: Methodology.
abstract: BACKGROUND
  The aim of this study was to test a 3-dimensional (3D) computer-assisted dental model analysis system that uses selected landmarks to describe tooth movement during treatment with an oral appliance.
  
  
  METHODS
  Dental casts of 70 patients diagnosed with obstructive sleep apnea and treated with oral appliances for a mean time of 7 years 4 months were evaluated with a 3D digitizer (MicroScribe-3DX, Immersion, San Jose, Calif) compatible with the Rhinoceros modeling program (version 3.0 SR3c, Robert McNeel & Associates, Seattle, Wash). A total of 86 landmarks on each model were digitized, and 156 variables were calculated as either the linear distance between points or the distance from points to reference planes. Four study models for each patient (maxillary baseline, mandibular baseline, maxillary follow-up, and mandibular follow-up) were superimposed on 2 sets of reference points: 3 points on the palatal rugae for maxillary model superimposition, and 3 occlusal contact points for the same set of maxillary and mandibular model superimpositions. The patients were divided into 3 evaluation groups by 5 orthodontists based on the changes between baseline and follow-up study models.
  
  
  RESULTS
  Digital dental measurements could be analyzed, including arch width, arch length, curve of Spee, overbite, overjet, and the anteroposterior relationship between the maxillary and mandibular arches. A method error within 0.23 mm in 14 selected variables was found for the 3D system. The statistical differences in the 3 evaluation groups verified the division criteria determined by the orthodontists.
  
  
  CONCLUSIONS
  The system provides a method to record 3D measurements of study models that permits computer visualization of tooth position and movement from various perspectives.
authors.affiliation: Department of Orthodontics, Faculty of Stomatology, Capital University of Medical Sciences, Beijing, China. huichen@interchange.ubc.ca
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Alan A
authors.initials: AA
authors.lastname: Lowe
authors.forename: Fernanda Riberiro
authors.initials: FR
authors.lastname: de Almeida
authors.forename: Mary
authors.initials: M
authors.lastname: Wong
authors.forename: John A
authors.initials: JA
authors.lastname: Fleetham
authors.forename: Bangkang
authors.initials: B
authors.lastname: Wang
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D002508:Cephalometry; D003198:Computer Simulation; D003724:Dental Arch / Q000033:anatomy & histology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008137:Longitudinal Studies; D008954:Models, Biological; D003765:Models, Dental; D009967:Orthodontic Appliances; D010363:Pattern Recognition, Automated; D020181:Sleep Apnea, Obstructive / Q000628:therapy; D013382:Subtraction Technique; D014087:Tooth Movement Techniques / Q000295:instrumentation*