title: The influence of altered occlusion on pro-inflammatory cytokine levels in the TMJ synovial tissues of rats.
abstract: OBJECTIVE
  The aim of this study was to evaluate whether altered occlusion affects both the condylar cartilage thickness and the cytokine levels of the TMJs of rats.
  
  
  METHODS
  Thirty adult-male rats (n=30) were randomly assigned to three experimental conditions: a control group that underwent sham operations with unaltered occlusion; an FPDM group that underwent functional posterior displacement of the mandible that was induced by an incisor guiding appliance; and an iOVD group in which the increased occlusal vertical dimension was induced in the molars. The rats were subjected to the FPDM or iOVD model for 14 days and then killed. Both the right and left TMJs were removed and randomly assigned to examination with staining or immunoassay techniques. Toluidine blue staining was used to measure the thicknesses of the four layers of the articular cartilage (i.e., the fibrous, proliferating, mature, and hypertrophic layers). ELISA assays were used to assess the concentrations of the pro-inflammatory cytokines IL-1α, IL-1β, IL-6, and tumour necrosis factor (TNF-α). The measurements of the articular cartilage layers and cytokine concentrations were analyzed with ANOVA and Tukey's tests and Kruskal-Wallis and Dunn tests, respectively (α=5%).
  
  
  RESULTS
  The thickness of articular cartilage in the FPDM group (0.3±0.03mm) was significantly greater than those of the control (0.2±0.01mm) and iOVD (0.25±0.03mm) groups. No significant difference was observed between the control and iOVD groups. The four articular cartilage layers were thicker in the FPDM group than in the control and iOVD groups, and the latter two groups did not differ one from each other. Both the FPDM and iOVD groups exhibited higher cytokine levels than did the control (p<0.05) group. Compared to the FPDM group, the iOVD group exhibited significantly higher levels of IL-1β and TNF-α.
  
  
  CONCLUSIONS
  Both models induced inflammation in the TMJ and caused significant structural changes in the TMJ and surrounding tissues.
authors.affiliation: Department of Physiological Sciences, Piracicaba Dental School, UNICAMP, Av. Limeira, 901, CEP 13414-903 Piracicaba, São Paulo, Brazil.
authors.forename: Sidney R
authors.initials: SR
authors.lastname: Figueroba
authors.affiliation: Department of Physiological Sciences, Piracicaba Dental School, UNICAMP, Av. Limeira, 901, CEP 13414-903 Piracicaba, São Paulo, Brazil.
authors.forename: Marina Passarela
authors.initials: MP
authors.lastname: Desjardins
authors.affiliation: Department of Physiological Sciences, Piracicaba Dental School, UNICAMP, Av. Limeira, 901, CEP 13414-903 Piracicaba, São Paulo, Brazil.
authors.forename: Luiz E N
authors.initials: LE
authors.lastname: Ferreira
authors.affiliation: Department of Physiological Sciences, Piracicaba Dental School, UNICAMP, Av. Limeira, 901, CEP 13414-903 Piracicaba, São Paulo, Brazil.
authors.forename: Luciana A
authors.initials: LA
authors.lastname: Berto
authors.affiliation: Department of Orthodontics, Araras Dental School, FHO/UNIARARAS, Av. Maximiliano Baruto, 500, Jd Universitário, São Paulo, Brazil.
authors.forename: Heloisa Cristina
authors.initials: HC
authors.lastname: Valdrighi
authors.affiliation: Department of Physiological Sciences, Piracicaba Dental School, UNICAMP, Av. Limeira, 901, CEP 13414-903 Piracicaba, São Paulo, Brazil. Electronic address: fcgroppo1@yahoo.com.br.
authors.forename: Francisco C
authors.initials: FC
authors.lastname: Groppo
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism* / Q000503:physiopathology*; D016207:Cytokines / Q000378:metabolism*; D003766:Dental Occlusion; D004797:Enzyme-Linked Immunosorbent Assay; D008297:Male; D008335:Mandibular Condyle / Q000378:metabolism / Q000503:physiopathology; D011897:Random Allocation; D051381:Rats; D013704:Temporomandibular Joint / Q000378:metabolism* / Q000503:physiopathology*
chemical_list: D016207:Cytokines
keywords: Animal model; Cartilage; Cytokines; Dental occlusion; Endochondral ossification; Temporomandibular joint