title: The reliability of an easy measuring method for abutment convergence angle with a computer-aided design (CAD) system.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the intra-rater reliability and inter-rater reliability of three different methods using a drawing protractor, a digital protractor after tracing, and a CAD system.
  
  
  METHODS
  Twenty-four artificial abutments that had been prepared by dental students were used in this study. Three dental students measured the convergence angles by each method three times. Bland-Altman plots were applied to examine the overall reliability by comparing the traditional tracing method with a new method using the CAD system. Intraclass Correlation Coefficients (ICC) evaluated intra-rater reliability and inter-rater reliability.
  
  
  RESULTS
  All three methods exhibited high intra-rater and inter-rater reliability (ICC>0.80, P<.05). Measurements with the CAD system showed the highest intra-rater reliability. In addition, it showed improved inter-rater reliability compared with the traditional tracing methods.
  
  
  CONCLUSIONS
  Based on the results of this study, the CAD system may be an easy and reliable tool for measuring the abutment convergence angle.
authors.affiliation: Department of Prosthodontics, Seoul National University School of Dentistry, Seoul, Republic of Korea.
authors.forename: Yong-Joon
authors.initials: YJ
authors.lastname: Seo
authors.affiliation: Department of Dentistry, St. Catholic Hospital, Catholic University of Korea, Suwon, Republic of Korea.
authors.forename: Taek-Ka
authors.initials: TK
authors.lastname: Kwon
authors.affiliation: Department of Prosthodontics, Seoul National University School of Dentistry, Seoul, Republic of Korea.
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Han
authors.affiliation: Department of Prosthodontics, Seoul National University School of Dentistry, Seoul, Republic of Korea.
authors.forename: Jai-Bong
authors.initials: JB
authors.lastname: Lee
authors.affiliation: Department of Prosthodontics, Seoul National University School of Dentistry, Seoul, Republic of Korea.
authors.forename: Sung-Hun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Prosthodontics, Seoul National University School of Dentistry, Seoul, Republic of Korea.
authors.forename: In-Sung
authors.initials: IS
authors.lastname: Yeo
keywords: Computer-aided design; Convergence angle; Dental abutments; Prosthodontic tooth preparation; Validation studies