title: Coordinate geometry method for capturing and evaluating crown preparation geometry.
abstract: BACKGROUND
  A validated universal method requiring no human input is needed to capture and evaluate preparation geometries in a manner that can be used to see the correlation of different parameters.
  
  
  OBJECTIVE
  The purpose of this study was to present a method of capturing and evaluating crown preparation geometry.
  
  
  METHODS
  One manually machined acrylic resin block and 9 randomly selected preparations for ceramic complete crowns prepared by general dentists were selected and prepared. The specimens were scanned (3D scanner; Nobel Biocare), and buccolingual and mesiodistal cross section images were collected. The images were imported into digitizing software (Engauge Digitizer 4.1) to convert the outlines into x and y coordinates. Six points were chosen by using a set of algorithms, and the resulting parameters were calculated.
  
  
  RESULTS
  The acrylic resin block was milled with a 12 degree total occlusal convergence (TOC) instrument producing a 12.83 degree TOC. For the other specimens, average TOC values ranged from 18 degrees to 52 degrees. The mean average margin width was 0.70 mm, and the mean average base dimension was 6.23 mm. The surface area/volume ratio, resistance length, and limiting taper were also calculated.
  
  
  CONCLUSIONS
  The method described provides a basis for accurately evaluating preparation geometry without human input.
authors.affiliation: Postgraduate student, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. Electronic address: janine.tiu@gmail.com.
authors.forename: Janine
authors.initials: J
authors.lastname: Tiu
authors.affiliation: Senior Lecturer, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: J Neil
authors.initials: JN
authors.lastname: Waddell
authors.affiliation: Senior Lecturer, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: Basil
authors.initials: B
authors.lastname: Al-Amleh
authors.affiliation: Lecturer, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: Wendy-Ann
authors.initials: WA
authors.lastname: Jansen van Vuuren
authors.affiliation: Professor, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Swain
mesh_terms: D000465:Algorithms; D001641:Bicuspid / Q000033:anatomy & histology; D017076:Computer-Aided Design; D003442:Crowns; D003481:Cuspid / Q000033:anatomy & histology; D017268:Dental Prosthesis Retention; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D008963:Molar / Q000033:anatomy & histology; D009811:Odontometry / Q000706:statistics & numerical data; D012984:Software; D019237:Tooth Cervix / Q000033:anatomy & histology; D019228:Tooth Crown / Q000033:anatomy & histology; D019231:Tooth Preparation, Prosthodontic / Q000706:statistics & numerical data*