title: Calcification of degenerating tissues in the periodontal ligament during tooth movement.
abstract: OBJECTIVE
  Calcification of degenerating tissues in the periodontal ligament (PDL) during tooth movement was investigated longitudinally.
  
  
  METHODS
  Upper first molars of male Wistar rats were moved lingually for 1, 7 and 21 d, following which unfixed undecalcified sections of the lingual PDL (in the pressure zone) were examined histologically, histochemically (autoradiography and electron probe microanalysis).
  
  
  RESULTS
  On d 1 of tooth movement, degenerating tissues, together with some calcified particles, were visible in the pressure zone of the lingual PDL. On d 7, substantial calcified aggregations were seen in the degenerating tissues, predominantly situated between the bone and root. This was confirmed by the 45Ca autoradiography. On d 21 of tooth movement, large calcified aggregations were still clearly evident between the bone and root.
  
  
  CONCLUSIONS
  This calcification of the degenerating tissues is a self-defense response of the living body to prevent direct contact between alveolar bone and the tooth root during compression of the PDL, so preventing friction between them and the development of ankylosis.
authors.affiliation: Department of Orthodontics, School of Dental Medicine, Tsurumi University, Yokohama, Japan. nakamura-ys@tsurumi-u.ac.jp
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Tanaka
authors.forename: Koji
authors.initials: K
authors.lastname: Noda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Shimpo
authors.forename: Takashi
authors.initials: T
authors.lastname: Oikawa
authors.forename: Ayao
authors.initials: A
authors.lastname: Hirashita
authors.forename: Tadafumi
authors.initials: T
authors.lastname: Kawamoto
authors.forename: Kenzo
authors.initials: K
authors.lastname: Kawasaki
mesh_terms: D000539:Alveolar Process / Q000473:pathology; D000818:Animals; D001345:Autoradiography; D002114:Calcinosis / Q000209:etiology*; D002118:Calcium / Q000032:analysis; D004577:Electron Probe Microanalysis; D008297:Male; D008855:Microscopy, Electron, Scanning; D009999:Ossification, Heterotopic / Q000209:etiology; D010510:Periodontal Diseases / Q000209:etiology*; D010513:Periodontal Ligament / Q000473:pathology*; D010758:Phosphorus / Q000032:analysis; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014087:Tooth Movement Techniques; D014092:Tooth Root / Q000473:pathology
chemical_list: D010758:Phosphorus; D002118:Calcium