title: A cone-beam computed tomography study of the root canal morphology of mandibular first premolars and the location of root canal orifices and apical foramina in a Chinese subpopulation.
abstract: BACKGROUND
  Successful root canal treatment is dependent on detailed knowledge of the morphology of the root canal system. The aim of this study was to investigate the morphology of the root canal systems of mandibular first premolars and the location of root canal orifices and apical foramina in a Chinese subpopulation using cone-beam computed tomography scanning.
  
  
  METHODS
  A total of 440 cone-beam computed tomographic images of mandibular first premolars were obtained from 238 patients. Tooth position, root canal morphology, the distance between the apical foramen and the anatomic apex, and the distance between the 2 root canal orifices of mandibular first premolars with 2 root canals were investigated. The Fisher exact test was used to analyze the correlation between the number of root canals and tooth position.
  
  
  RESULTS
  Overall, 1.14% (n = 5) of the teeth had a C-shaped root canal system, 77.14% (n = 335) had 1 root canal, and 22.05% (n = 97) had 2 root canals from type II to type V. The remaining 0.68% (n = 3) were classified as type VIII, which had 3 root canals. The most frequent distribution of the distance between the apical foramen and the anatomic apex in 335 mandibular first premolars with 1 root canal was 1-2 mm (n = 192). The distance between the apical foramen and the anatomic apex of mandibular first premolars with 2 root canals was in accord with that of mandibular first premolars with 1 root canal. The distance between the 2 root canal orifices of mandibular first premolars with 2 root canals was approximately 13 mm.
  
  
  CONCLUSIONS
  Most mandibular first premolars had 1 root canal. More than 1 of 5 mandibular first premolars had complex root canal systems (with 2 or more root canals). This study provides supplemental information about the root canals of mandibular first premolars in a Chinese subpopulation.
authors.affiliation: Department of Endodontics, School of Stomatology, Shandong University, Shandong Provincial Key Laboratory of Oral Biomedicine, Jinan, China.
authors.forename: Haibing
authors.initials: H
authors.lastname: Yang
authors.forename: Cheng
authors.initials: C
authors.lastname: Tian
authors.forename: Guoju
authors.initials: G
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Yang
authors.forename: Xuan
authors.initials: X
authors.lastname: Han
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D044466:Asian People; D001641:Bicuspid / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D016009:Chi-Square Distribution; D002681:China; D054893:Cone-Beam Computed Tomography; D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D006801:Humans; D008334:Mandible; D019227:Tooth Apex / Q000033:anatomy & histology / Q000000981:diagnostic imaging*