title: Incisor disocclusion in rats affects mandibular condylar cartilage at the cellular level.
abstract: The effect of altered occlusion on the mandibular condylar cartilage remains unclear.
  
  
  OBJECTIVE
  This study investigated the effect of unilateral incisor disocclusion on cartilage thickness, on mitotic activity and on chondrocytes maturation and differentiation in the mandibular condylar cartilage of rats.
  
  
  METHODS
  The upper and lower left incisors were trimmed 2mm every second day in five rats. In other five rats, the incisor occlusion was not altered. Condylar tissues from both sides of each mandible were processed and stained for Herovici's stain and immunohistochemistry for bromodeoxyuridine (BrdU), transforming growth factor-beta1 (TGF-beta1), alkaline phosphatase (ALP) and osteocalcin (OCN). Measurements of cartilage thickness and the numbers of immunopositive cells for each antibody were analysed by one-way analysis of variance (ANOVA).
  
  
  RESULTS
  No significant differences were observed in cartilage thickness after 7 days of unilateral incisor disocclusion. However, the numbers of immunopositive cells for BrdU as a marker of DNA synthesising cells, TGF-beta1 as a marker of chondrocytes differentiation, and ALP and OCN as markers of chondrocytes maturation, were significant higher in the cartilage cells on both sides when incisor occlusion was unilaterally altered. Interestingly, alkaline phosphatase was highly expressed on the condylar side of incisor disocclusion, whereas osteocalcin was highly expressed on the side opposite to the incisor disocclusion.
  
  
  CONCLUSIONS
  It is demonstrated that after 7 days, unilateral incisor disocclusion affects the mandibular condylar cartilage at the cellular level by increasing the mitotic activity and by accelerating chondrocytes maturation. Chondrocytes maturation appears more accelerated on the side opposite to incisor disocclusion.
authors.affiliation: Department of Oral Biology and Pathology, School of Dentistry, The University of Queensland, QLD, Australia. g.ramirez@uq.edu.au
authors.forename: G O
authors.initials: GO
authors.lastname: Ramirez-Yañez
authors.forename: T J
authors.initials: TJ
authors.lastname: Daley
authors.forename: A L
authors.initials: AL
authors.lastname: Symons
authors.forename: W G
authors.initials: WG
authors.lastname: Young
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis; D000818:Animals; D001973:Bromodeoxyuridine / Q000032:analysis; D002358:Cartilage, Articular / Q000737:chemistry / Q000473:pathology*; D002454:Cell Differentiation / Q000502:physiology; D019902:Chondrocytes / Q000473:pathology; D007180:Incisor / Q000473:pathology / Q000503:physiopathology*; D008310:Malocclusion / Q000473:pathology / Q000503:physiopathology*; D008335:Mandibular Condyle / Q000737:chemistry / Q000473:pathology / Q000503:physiopathology*; D008938:Mitosis / Q000502:physiology; D015675:Osteocalcin / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D016212:Transforming Growth Factor beta / Q000032:analysis; D053773:Transforming Growth Factor beta1
chemical_list: C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D015675:Osteocalcin; D000469:Alkaline Phosphatase; D001973:Bromodeoxyuridine