title: Microscopic analysis of molar--incisor malformation.
abstract: OBJECTIVE
  Molar-incisor malformation (MIM) is a newly discovered type of dental anomaly that involves a characteristic root malformation of the permanent first molars. The aim of this study was to reveal the microstructure of MIM teeth in order to determine their origin.
  
  
  METHODS
  Four MIM teeth were extracted from a 9-year-old girl due to severe mobility. The detailed microstructure of the teeth was determined by examinations with micro-computed tomography (micro-CT), hematoxylin and eosin (H&E) staining, immunohistochemical staining, and scanning electron microscopy to reveal the detailed microstructure.
  
  
  RESULTS
  Micro-CT and H&E staining revealed the pulpal floor comprising three layers: upper, middle, and lower. Amorphous hard tissues and hyperactive cells were observed in the middle layer of the pulpal floor, and the cells stained positively for dentin sialoprotein and osteocalcin, but not for collagen XII.
  
  
  CONCLUSIONS
  The results of the present study imply that MIM-affected molars probably result from inappropriate differentiation of the apical pulp and dental follicle.
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Hyo-Seol
authors.initials: HS
authors.lastname: Lee
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Soo-Hyun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea; Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Seong-Oh
authors.initials: SO
authors.lastname: Kim
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea; Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Byung-Jai
authors.initials: BJ
authors.lastname: Choi
authors.affiliation: Division in Anatomy & Developmental Biology, Department of Oral Biology, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Sung-Won
authors.initials: SW
authors.lastname: Cho
authors.affiliation: Department of General Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea.
authors.forename: Wonse
authors.initials: W
authors.lastname: Park
authors.affiliation: Department of Pediatric Dentistry, College of Dentistry, Yonsei University, Seoul, Republic of Korea; Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Republic of Korea. Electronic address: Songjs@yuhs.ac.
authors.forename: Je Seon
authors.initials: JS
authors.lastname: Song
mesh_terms: D002648:Child; D005260:Female; D006801:Humans; D007180:Incisor / Q000002:abnormalities* / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D008963:Molar / Q000002:abnormalities* / Q000601:surgery / Q000648:ultrastructure*; D014081:Tooth Extraction; D055114:X-Ray Microtomography