title: [Investigation of root and canal morphology of human primary mandibular second molar by cone-beam CT].
abstract: OBJECTIVE
  To investigate the root and canal morphology of primary mandibular second molars in a Chinese population by cone-beam CT(CBCT).
  
  
  METHODS
  A total of 305 CBCT images of 305 children aged 4-8 years were collected, who came to West China Dental Hospital from October, 2011 to March, 2012 due to supernumerary teeth, dental trauma, orthodontic treatment or oral maxillofacial tumor. Primary mandibular second molars which roots were full developed, without periapical infection or apical root resorption were enrolled. All the images were analyzed by two researchers. The data were statistically analyzed by software SPSS 19.0.
  
  
  RESULTS
  Four hundred and thirty-seven primary mandibular second molars(PMSM) showed single mesial root except one which had two. Three hundred and twenty-five (74.4%) teeth had one distal root, 111(25.4%) teeth had two and one had three. There were 424(97.0%) teeth which had two mesial canals and 13(3.0%) had one.One hundred and three(23.6%) teeth had one distal root with one canal, 222(50.8%) had one distal root with two canals, 106(24.3%) had two distal roots with two canals, 5(1.1%) had two roots with three canals and 1(0.2%) had three roots with three canals. The root canal system of PMSM had ten variants in this study. The prevalence of three-rooted PMSM had significant differences from different genders (P = 0.000) and different sides (P = 0.028).
  
  
  CONCLUSIONS
  Majority of primary mandibular second molars had two roots, and the minority had three roots. The prevalence of three-rooted molars in males were higher than that in females. Mesial and distal roots of primary mandibular second molars often had two canals.
authors.affiliation: Department of Pediatric Dentistry, West China School of Stomatology, Sichuan University, Chengdu 610041, China.
authors.forename: Chan
authors.initials: C
authors.lastname: Yang
authors.forename: Ran
authors.initials: R
authors.lastname: Yang
authors.forename: Jing
authors.initials: J
authors.lastname: Zou
mesh_terms: D044466:Asian People; D002648:Child; D002675:Child, Preschool; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008963:Molar / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D014092:Tooth Root / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D014094:Tooth, Deciduous / Q000033:anatomy & histology / Q000000981:diagnostic imaging*