title: Morphometric evaluation of condylar cartilage of growing rats in response to mandibular retractive forces.
abstract: BACKGROUND
  The mandibular condylar surface is made up of four layers, i.e., an external layer composed of dense connective tissue, followed by a layer of undifferentiated cells, hyaline cartilage and bone. Few studies have demonstrated the behavior of the condylar cartilage when the mandible is positioned posteriorly, as in treatments for correcting functional Class III malocclusion.
  
  
  OBJECTIVE
  The aim of this study was to assess the morphologic and histological aspects of rat condyles in response to posterior positioning of the mandible.
  
  
  METHODS
  Thirty five-week-old male Wistar rats were selected and randomly divided into two groups: A control group (C) and an experimental group (E) which received devices for inducing mandibular retrusion. The animals were euthanized at time intervals of 7, 21 and 30 days after the experiment had began. For histological analysis, total condylar thickness was measured, including the proliferative, hyaline and hypertrophic layers, as well as each layer separately, totaling 30 measurements for each parameter of each animal.
  
  
  RESULTS
  The greatest difference in cartilage thickness was observed in 21 days, although different levels were observed in the other periods. Group E showed an increase of 39.46% in the total layer, reflected by increases in the thickness of the hypertrophic (42.24%), hyaline (46.92%) and proliferative (17.70%) layers.
  
  
  CONCLUSIONS
  Posteriorly repositioning the mandible produced a series of histological and morphological responses in the condyle, suggesting condylar and mandibular adaptation in rats.
authors.forename: Milena Peixoto Nogueira
authors.initials: MP
authors.lastname: de Sá
authors.forename: Jacqueline Nelisis
authors.initials: JN
authors.lastname: Zanoni
authors.forename: Carlos Luiz Fernandes
authors.initials: CL
authors.lastname: de Salles
authors.forename: Fabrício Dias
authors.initials: FD
authors.lastname: de Souza
authors.forename: Uhana Seifert Guimarães
authors.initials: US
authors.lastname: Suga
authors.forename: Raquel Sano Suga
authors.initials: RS
authors.lastname: Terada
mesh_terms: D000818:Animals; D002356:Cartilage / Q000033:anatomy & histology / Q000254:growth & development*; D008297:Male; D008313:Malocclusion, Angle Class III / Q000503:physiopathology*; D008335:Mandibular Condyle / Q000033:anatomy & histology / Q000254:growth & development*; D051381:Rats; D017208:Rats, Wistar; D063173:Retrognathia / Q000503:physiopathology*; D018709:Statistics, Nonparametric
keywords: Angle Class III malocclusion; Articular cartilage; Mandibular condyle