title: Clinical tooth preparations and associated measuring methods: a systematic review.
abstract: BACKGROUND
  The geometries of tooth preparations are important features that aid in the retention and resistance of cemented complete crowns. The clinically relevant values and the methods used to measure these are not clear.
  
  
  OBJECTIVE
  The purpose of this systematic review was to retrieve, organize, and critically appraise studies measuring clinical tooth preparation parameters, specifically the methodology used to measure the preparation geometry.
  
  
  METHODS
  A database search was performed in Scopus, PubMed, and ScienceDirect with an additional hand search on December 5, 2013. The articles were screened for inclusion and exclusion criteria and information regarding the total occlusal convergence (TOC) angle, margin design, and associated measuring methods were extracted. The values and associated measuring methods were tabulated.
  
  
  RESULTS
  A total of 1006 publications were initially retrieved. After removing duplicates and filtering by using exclusion and inclusion criteria, 983 articles were excluded. Twenty-three articles reported clinical tooth preparation values. Twenty articles reported the TOC, 4 articles reported margin designs, 4 articles reported margin angles, and 3 articles reported the abutment height of preparations. A variety of methods were used to measure these parameters.
  
  
  CONCLUSIONS
  TOC values seem to be the most important preparation parameter. Recommended TOC values have increased over the past 4 decades from an unachievable 2- to 5-degree taper to a more realistic 10 to 22 degrees. Recommended values are more likely to be achieved under experimental conditions if crown preparations are performed outside of the mouth. We recommend that a standardized measurement method based on the cross sections of crown preparations and standardized reporting be developed for future studies analyzing preparation geometry.
authors.affiliation: Doctoral student, Sir John Walsh Research Institute, 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, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: Basil
authors.initials: B
authors.lastname: Al-Amleh
authors.affiliation: Senior Lecturer, Department of Oral Rehabilitation, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: J Neil
authors.initials: JN
authors.lastname: Waddell
authors.affiliation: Associate Professor, Department of Oral Sciences, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: Warwick J
authors.initials: WJ
authors.lastname: Duncan
mesh_terms: D000044:Dental Abutments; D017268:Dental Prosthesis Retention; D006801:Humans; D009811:Odontometry / Q000379:methods*; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*