title: Cone-beam computed tomography for the assessment of root-crown ratios of the maxillary and mandibular incisors in a Korean population.
abstract: OBJECTIVE
  This retrospective, cross-sectional study aimed to establish reference data for normal crown and root lengths and the root-crown ratios (R/C ratios) for the mature maxillary and mandibular incisors in a Korean population by using cone-beam computed tomography (CBCT).
  
  
  METHODS
  We included 672 Korean patients (141 men and 531 women; mean age, 27.2 ± 7.7 years) who underwent CBCT examinations during various dental treatments. Crown and root lengths and the R/C ratios of the maxillary and mandibular incisors were measured using CBCT data, which were analyzed to detect significant differences between demographic factors as well as sagittal and vertical skeletal or occlusal relationships.
  
  
  RESULTS
  Teeth of the same type in each half-arch were symmetrical. The mean R/C ratios varied from 1.1 to 1.2 for the maxillary incisors and from 1.3 to 1.4 for the mandibular incisors. Crown and root lengths were greater in men than in women, regardless of tooth type. Root lengths and R/C ratios for the mandibular incisors were significantly greater in patients with skeletal Class II malocclusion or an excessive overjet than in the other patients. The R/C ratios for the mandibular incisors were lower in patients with an open bite than in those with a normal or deep bite. Moreover, the R/C ratios for the mandibular incisors increased with age.
  
  
  CONCLUSIONS
  The data obtained in our study can serve as reference values for crown and root lengths and the R/C ratios for the maxillary and mandibular incisors in the Korean population.
authors.affiliation: Department of Orthodontics, The Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Sung-Hwan
authors.initials: SH
authors.lastname: Choi
authors.affiliation: Private Practice, Seongnam, Korea.
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Private Practice, Seongnam, Korea.
authors.forename: Cheol-Soon
authors.initials: CS
authors.lastname: Kim
authors.affiliation: Department of Orthodontics, The Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Hyung-Seog
authors.initials: HS
authors.lastname: Yu
authors.affiliation: Department of Orthodontics, The Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Chung-Ju
authors.initials: CJ
authors.lastname: Hwang
keywords: Cone-beam computed tomography; Incisor; Population; Tooth crown; Tooth root