title: Reporting numeric values of complete crowns. Part 1: Clinical preparation parameters.
abstract: BACKGROUND
  An implemented objective measuring system for measuring clinical tooth preparations does not exist.
  
  
  OBJECTIVE
  The purpose of this study was to compare clinically achieved tooth preparations for ceramic crowns by general dentists with the recommended values in the literature with an objective measuring method.
  
  
  METHODS
  Two hundred thirty-six stone dies prepared for anterior and posterior complete ceramic crown restorations (IPS e.max Press; Ivoclar Vivadent) were collected from dental laboratories. The dies were scanned and analyzed using the coordinate geometry method. Cross-sectioned images were captured, and the average total occlusal convergence angle, margin width, and abutment height for each preparation was measured and presented with associated 95% confidence intervals.
  
  
  RESULTS
  The average total occlusal convergence angles for each tooth type was above the recommended values reported in the literature. The average margin widths (0.40 to 0.83 mm) were below the minimum recommended values (1 to 1.5 mm). The tallest preparations were maxillary canines (5.25 mm), while the shortest preparations were mandibular molars (1.87 mm).
  
  
  CONCLUSIONS
  Complete crown preparations produced in general practice do not achieve the recommended values found in the literature. However, these recommended values are not based on clinical trials, and the effects of observed shortfalls on the clinical longevity of these restorations are not predictable.
authors: Doctoral student, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. Electronic address: janine.tiu@gmail.com.
authors: Janine
authors: J
authors: Tiu
authors: Senior lecturer and prosthodontist, Department of Oral Rehabilitation, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors: Basil
authors: B
authors: Al-Amleh
authors: Associate Professor, Department of Oral Rehabilitation, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors: J Neil
authors: JN
authors: Waddell
authors: Professor, Department of Oral Sciences, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors: Warwick J
authors: WJ
authors: Duncan
mesh_terms: D001641:Bicuspid / Q000033:anatomy & histology; D017076:Computer-Aided Design; D003442:Crowns / Q000706:statistics & numerical data*; D003481:Cuspid / Q000033:anatomy & histology; D000044:Dental Abutments; D003776:Dental Porcelain / Q000737:chemistry; D005792:General Practice, Dental; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007180:Incisor / Q000033:anatomy & histology; D007754:Laboratories, Dental; D003765:Models, Dental; D008963:Molar / Q000033:anatomy & histology; D061848:Optical Imaging / Q000379:methods; D012984:Software; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000706:statistics & numerical data*
chemical_list: C508050:IPS e.max Press; D003776:Dental Porcelain