title: Incidence and relationship of an additional root in the mandibular first permanent molar and primary molars.
abstract: OBJECTIVE
  The mandibular first permanent and primary molars occasionally have an additional root located distolingually. This study aimed to determine the incidences of an additional root in these molars and their relationship.
  
  
  METHODS
  This study involved 4050 children for whom periapical radiographs of the mandibular molar area were available. The incidence of an additional root for each molar was calculated and the pattern of concurrent additional roots in different molars was also investigated.
  
  
  RESULTS
  Additional roots were present in 33.1%, 27.8%, and 9.7% of the first permanent, second primary, and first primary molars, respectively. When an additional root was present in a primary molar, the probability of the posterior adjacent molar also having an additional root was greater than 94.3%.
  
  
  CONCLUSIONS
  The presence of an additional root in a primary molar can be used to predict the presence of an additional root in molars posterior to it.
authors.affiliation: Department of Pediatric Dentistry, Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Je Seon
authors.initials: JS
authors.lastname: Song
authors.forename: Seong-Oh
authors.initials: SO
authors.lastname: Kim
authors.forename: Byung-Jai
authors.initials: BJ
authors.lastname: Choi
authors.forename: Hyung-Jun
authors.initials: HJ
authors.lastname: Choi
authors.forename: Heung-Kyu
authors.initials: HK
authors.lastname: Son
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Lee
mesh_terms: D002648:Child; D002675:Child, Preschool; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008963:Molar / Q000033:anatomy & histology*; D014092:Tooth Root / Q000033:anatomy & histology*; D014094:Tooth, Deciduous / Q000033:anatomy & histology