title: Effect of aging on the rat condylar fracture model evaluated by bromodeoxyuridine immunohistochemistry.
abstract: OBJECTIVE
  The effect of aging on the recovery of cellular proliferative ability in the experimentally fractured rat condyle was studied by bromodeoxyuridine (BrdU) immunohistochemistry.
  
  
  METHODS
  The experimental animals (male Sprague-Dawley rats; n = 33, unilateral condylar fracture and sham operation) were divided into three age groups: 3, 6, and 36-weeks old. The cell proliferation was evaluated by the BrdU labeling index (LI) in the intermediate cell layer of the condyle at 1, 2, 4, 6, and 8 weeks after the fracture.
  
  
  RESULTS
  The cell kinetics of both condyles was affected by the temporomandibular joint dysfunction due to the unilateral condylar fracture. In all age groups, the fracture healed within 4 weeks. The LI of the nonfractured as well as fractured condyles decreased strikingly up to 2 weeks, and then only slightly increased at 4 weeks after the fracture. The LIs of the fractured condyles were lower than those of the control throughout the experiment regardless of age. Eight weeks after the fracture the percentage of recovery of the LI in the fractured condyle (LIs of fractured condyle in the fracture group/LIs of right condyle in the sham group) was 45.1% in 3-week-old-animals, 21.2% in 6-week-old-animals, and 16.1% in 36-week-old-animals.
  
  
  CONCLUSIONS
  This study shows that the recovery of cell proliferation in the fractured condyle depends on age.
authors.affiliation: Second Department of Oral and Maxillofacial Surgery, Nagasaki University, School of Dentistry, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Sekine
authors.forename: K
authors.initials: K
authors.lastname: Sano
authors.forename: T
authors.initials: T
authors.lastname: Inokuchi
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001861:Bone Regeneration / Q000502:physiology; D001973:Bromodeoxyuridine; D002455:Cell Division; D017102:Fracture Healing / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008335:Mandibular Condyle / Q000293:injuries* / Q000502:physiology; D008337:Mandibular Fractures / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001973:Bromodeoxyuridine