title: Radiographic assessment of clinical root-crown ratios of permanent teeth in a healthy Korean population.
abstract: OBJECTIVE
  The aim of this study was to determine the absolute value of the root/crown ratio (R/C ratio) using panoramic radiographs (PRGs) in a healthy Korean population.
  
  
  METHODS
  In total, 99 patient radiographs (of 50 males and 49 females subjects; aged 16 to 24 years old) were examined, and 2,770 teeth were analyzed. Crown lengths and root lengths were measured with modified Lind's measurements using PACS tools by two examiners in two separate sessions two months apart. All data were analyzed using SPSS. The independent t-test was used to assess for gender differences, and the paired t-test was used to compare both arches with a significance level of P<.05.
  
  
  RESULTS
  The mean R/C ratios varied from 1.29 to 1.89 (male: 1.28-1.84; females: 1.31-1.94). The highest R/C ratios were recorded for the mandibular canines (1.89), followed by the maxillary canines (1.79). The lowest R/C ratios were recorded for the maxillary second molars (1.31). In comparison with the maxillary teeth (1.29-1.78), the mandibular teeth yielded the higher R/C ratio (1.47-1.89), and this difference was significant in the females (P<.05). The difference between the genders was not statistically significant, except for the maxillary central incisors, mandibular canines and mandibular first premolars.
  
  
  CONCLUSIONS
  These data may enhance the understanding of the clinical R/C ratio as a useful guideline for determining the status of teeth and the ethnic difference.
authors.affiliation: Department of Advanced General Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Hee-Jung
authors.initials: HJ
authors.lastname: Yun
authors.affiliation: Department of Advanced General Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Jin-Sun
authors.initials: JS
authors.lastname: Jeong
authors.affiliation: Department of Advanced General Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Nan-Sim
authors.initials: NS
authors.lastname: Pang
authors.affiliation: Department of Maxillofacial Biomedical Engineering and Institute of Oral Biology, School of Dentistry, Kyung Hee University, Seoul, Republic of Korea.
authors.forename: Il-Keun
authors.initials: IK
authors.lastname: Kwon
authors.affiliation: Department of Advanced General Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Bock-Young
authors.initials: BY
authors.lastname: Jung
keywords: Ethnic differences; Panoramic radiograph; Prognosis of teeth; Root/Crown ratio