title: Effect of diet hardness on mandibular condylar cartilage metabolism.
abstract: OBJECTIVE
  To study the effect of diet hardness on condylar cartilage thickness, extracellular matrix composition, and expression of matrix metalloproteinase (MMP) -3, -8 and tissue inhibitor of metalloproteinase-1 (TIMP-1), by using immunohistochemical and morphometric methods.
  
  
  METHODS
  Seventy-two female Sprague Dawley rats were exposed to different dietary hardness, from soft to hard. MMP -3, -8, and TIMP-1 expression, cartilage thickness, cell count, and expression of type II collagen were studied. Analysis of variance among treatments was carried out followed by Bonferroni's comparisons test.
  
  
  RESULTS
  The ratio of MMP-3 and TIMP-1 immunopositive cartilage cells were similar in all age groups, whereas the number of MMP-8 positive cells decreased with age. A change of diet from soft to hard caused a significant decrease in the number of MMP-3 and MMP-8 and an increase in TIMP-1 positive cells. Cartilage thickness and area of type II collagen-positive staining were significantly affected by diet hardness.
  
  
  CONCLUSIONS
  The results show that a soft diet during growth increases collagenolytic activity and may increase the vulnerability of condylar cartilage.
authors.forename: Petri
authors.initials: P
authors.lastname: Tiilikainen
authors.forename: Aune
authors.initials: A
authors.lastname: Raustia
authors.forename: Pertti
authors.initials: P
authors.lastname: Pirttiniemi
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology; D019902:Chondrocytes / Q000378:metabolism; D024043:Collagen Type II / Q000096:biosynthesis; D003799:Dental Stress Analysis; D004032:Diet / Q000009:adverse effects*; D005260:Female; D005502:Food / Q000009:adverse effects; D006244:Hardness; D008335:Mandibular Condyle / Q000378:metabolism*; D008409:Mastication / Q000502:physiology; D019278:Matrix Metalloproteinase 3 / Q000096:biosynthesis; D020784:Matrix Metalloproteinase 8 / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis
chemical_list: D024043:Collagen Type II; D019715:Tissue Inhibitor of Metalloproteinase-1; D019278:Matrix Metalloproteinase 3; D020784:Matrix Metalloproteinase 8