title: Cementocyte cell death occurs in rat cellular cementum during orthodontic tooth movement.
abstract: OBJECTIVE
  To clarify the mechanism of root resorption during orthodontic treatment, we examined cementocyte cell death and root resorption in the cellular cementum on the pressure side during experimental tooth movement.
  
  
  METHODS
  Using 8-week-old male Wistar rats, the right first molar was pushed mesiobuccally with a force of 40 g by a Ni-Ti alloy wire while the contralateral first molar was used as a control. Localization and number of cleaved caspase-3-positive and single-stranded DNA (ssDNA) - positive cells were evaluated using dual-label immunohistochemistry with anticleaved caspase-3 and anti-ssDNA antibodies. In addition, tartrate-resistant acid phosphatase (TRAP)-positive cells in the cellular cementum were evaluated using TRAP histochemical staining.
  
  
  RESULTS
  Caspase-3- and ssDNA-positive cells appeared at 12 hours, but were restricted to the compressed periodontal ligament (PDL) and not the cellular cementum. Cleaved caspase-3-positive cementocytes were observed in the cellular cementum adjacent to the compressed PDL on day 1. From days 2 to 4, the number of caspase-3- and ssDNA-positive cementocytes increased. TRAP-positive cells appeared on the cellular cementum at the periphery of the hyalinized tissue on day 7, and resorption progressed into the broad surface of the cementum by day 14.
  
  
  CONCLUSIONS
  Cementocytes adjacent to the hyalinized tissue underwent apoptotic cell death during orthodontic tooth movement, which might have been associated with subsequent root resorption.
authors.forename: Humihiro
authors.initials: H
authors.lastname: Matsuzawa
authors.forename: Naoko
authors.initials: N
authors.lastname: Toriya
authors.forename: Yuya
authors.initials: Y
authors.lastname: Nakao
authors.forename: Moe
authors.initials: M
authors.lastname: Konno-Nagasaka
authors.forename: Toshiya
authors.initials: T
authors.lastname: Arakawa
authors.forename: Miki
authors.initials: M
authors.lastname: Okayama
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
mesh_terms: D000818:Animals; D017209:Apoptosis; D003739:Dental Cementum / Q000166:cytology*; D007150:Immunohistochemistry; D008297:Male; D009532:Nickel; D009969:Orthodontic Wires; D010513:Periodontal Ligament / Q000166:cytology; D051381:Rats; D017208:Rats, Wistar; D012391:Root Resorption / Q000473:pathology*; D000071681:Tartrate-Resistant Acid Phosphatase; D014025:Titanium; D014087:Tooth Movement Techniques
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D000071681:Tartrate-Resistant Acid Phosphatase
keywords: Apoptosis; Cell death; Cementocyte; Orthodontic tooth movement; Root resorption