title: Molar root-incisor malformation: considerations of diverse developmental and etiologic factors.
abstract: OBJECTIVE
  The objective of this study was to evaluate the variation in the condition referred to as molar root-incisor malformation (MRIM) and elucidate the distribution of affected teeth. This study further aimed to identify associated environmental stressors.
  
  
  METHODS
  Individuals were identified through retrospective review of dental radiographs and through referral to the investigators. Histologic evaluation included examination of mineralized and decalcified sections of affected first permanent molar teeth.
  
  
  RESULTS
  Thirty cases of MRIM were identified, with all having affected first permanent molars with dysplastic root formation. The primary second molars were affected in 57% of the cases, with permanent anterior teeth being involved in 40% of the cases. A variety of medical conditions were associated with MRIM, the most common being neurologic. Several affected individuals reported no significant past medical history or environmental stressors.
  
  
  CONCLUSIONS
  The etiology of MRIM remains unclear, and this unique developmental defect of the first permanent molar roots appears to occur in populations throughout the world. Clinicians identifying the MRIM phenotype should carefully evaluate the permanent incisors for associated developmental defects that could result in pulpal necrosis.
authors.affiliation: Department of Pediatric Dentistry School of Dentistry, University of North Carolina, NC, USA.
authors.forename: John Timothy
authors.initials: JT
authors.lastname: Wright
authors.affiliation: Department of Diagnostic Sciences, School of Dentistry, University of North Carolina, NC, USA.
authors.forename: Alice
authors.initials: A
authors.lastname: Curran
authors.affiliation: Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Kyoung-Jin
authors.initials: KJ
authors.lastname: Kim
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry, Chonbuk National University, Jeonju-si, Jeollabuk-do, Korea.
authors.forename: Yeon-Mi
authors.initials: YM
authors.lastname: Yang
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry, Kyungpook National University, Daegu, Korea.
authors.forename: Soon-Hyeun
authors.initials: SH
authors.lastname: Nam
authors.affiliation: Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Teo Jeon
authors.initials: TJ
authors.lastname: Shin
authors.affiliation: Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Hong-Keun
authors.initials: HK
authors.lastname: Hyun
authors.affiliation: Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Young-Jae
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea; Department of Molecular Genetics & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea. Electronic address: pedoman@snu.ac.kr.
authors.forename: Jung-Wook
authors.initials: JW
authors.lastname: Kim
mesh_terms: D005260:Female; D006801:Humans; D007180:Incisor / Q000002:abnormalities* / Q000000981:diagnostic imaging; D008297:Male; D008963:Molar / Q000002:abnormalities* / Q000000981:diagnostic imaging; D009657:North Carolina; D010641:Phenotype; D011862:Radiography, Panoramic; D056910:Republic of Korea; D012189:Retrospective Studies; D012307:Risk Factors; D014071:Tooth Abnormalities / Q000209:etiology*; D014092:Tooth Root / Q000002:abnormalities* / Q000000981:diagnostic imaging