title: Age- and sex-related changes of mandibular condylar cartilage and subchondral bone: a histomorphometric and micro-CT study in rats.
abstract: OBJECTIVE
  To quantify the age- and sex-related changes in the rat condylar cartilage and subchondral bone.
  
  
  METHODS
  SD rats were obtained at the ages of 2, 3, 4, 5, 6 and 7 months. For each sex, the temporomandibular joints tissue blocks from four rats were subjected to histological assessment of cartilage thickness and subchondral bone architecture; for the remaining three rats, the mandibular condyles were delivered for gross measurement and evaluation of the mineralization and architecture properties of the subchondral bone by means of micro-CT.
  
  
  RESULTS
  Rapid decrease of cartilage thickness but increase of subchondral bone density occurred respectively from 2 to 3 and 3 to 4 months old in female and 2 to 4 and 3 to 5 months old in male (P<0.05), whereas rapid changes of subchondral bone architecture occurred from 3 to 4 months old in both sexes (P<0.05). The significant enlargement of condyle size occurred at 4 or 5 months old in female but at 5 or 6 months in male (P<0.05).
  
  
  CONCLUSIONS
  This study demonstrated that the rapid developmental changes of rat condylar cartilage and subchondral bone primarily occurred before 4 months of age, resulting in thinner cartilage but larger and thicker subchondral bone, and they were followed by rapid growth in condylar size. Sex differences were identified that the endochondral ossification of fibrocartilage and formation of subchondral bone were faster in female than in male rats, leading to the earlier enlargement of condyle in female than in male.
authors.affiliation: Department of Oral Anatomy and Physiology and TMD, School of Stomatology, Fourth Military Medical University, West Changle Road, No. 145, Xi'an 710032, Shaanxi, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Jiao
authors.forename: Juan
authors.initials: J
authors.lastname: Dai
authors.forename: Mei-Qing
authors.initials: MQ
authors.lastname: Wang
authors.forename: Li-Na
authors.initials: LN
authors.lastname: Niu
authors.forename: Shi-Bin
authors.initials: SB
authors.lastname: Yu
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Liu
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000254:growth & development*; D005260:Female; D008297:Male; D008335:Mandibular Condyle / Q000000981:diagnostic imaging / Q000254:growth & development*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D013194:Staining and Labeling; D055114:X-Ray Microtomography