title: Prevalence of 3-rooted primary mandibular second molars among chinese patients.
abstract: OBJECTIVE
  The purpose of this study was to determine the prevalence of 3-rooted primary mandibular second molar teeth in Chinese patients via vertical bitewing radiography.
  
  
  METHODS
  Vertical bitewing radiographs of 227 patients previously obtained from the Department of Pediatric Dentistry, Taichung Veterans General Hospital, Taichung City, Taiwan, from June 2004 to July 2007 were retrospectively screened and examined. Images of 185 patients (92 boys and 93 girls; mean age=5.6 [range=2.5-11.9] years old) with bilateral primary mandibular second molars were studied. The gender, symmetry, and frequencies of occurrence of 3-rooted primary mandibular second molars were compared.
  
  
  RESULTS
  Eighteen (9%) 3-rooted primary mandibular second molars were found in the 185 patients, with a bilateral incidence of a symmetrical distribution of 28% (5/18). The prevalence of 3-rooted primary second molars did not differ significantly between the mandible's right and left sides (P<.41), or with gender (P<.31).
  
  
  CONCLUSIONS
  The data presented here indicate that approximately one tenth of Chinese individuals have a 3-rooted primary mandibular second molar and that this condition is bilaterally symmetric in approximately one third of such individuals in a Taiwan hospital.
authors.affiliation: Section of Pediatric Dentistry, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Jeng-Fen
authors.initials: JF
authors.lastname: Liu
authors.forename: Pei-Wei
authors.initials: PW
authors.lastname: Dai
authors.forename: San-Yue
authors.initials: SY
authors.lastname: Chen
authors.forename: Heng-Li
authors.initials: HL
authors.lastname: Huang
authors.forename: Jui-Ting
authors.initials: JT
authors.lastname: Hsu
authors.forename: Wil-Lie
authors.initials: WL
authors.lastname: Chen
authors.forename: Ming-Gene
authors.initials: MG
authors.lastname: Tu
mesh_terms: D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008963:Molar / Q000002:abnormalities*; D015995:Prevalence; D016300:Radiography, Bitewing / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012737:Sex Factors; D014092:Tooth Root / Q000002:abnormalities*; D014094:Tooth, Deciduous / Q000002:abnormalities*