title: Hyperocclusion stimulates the expression of collagen type XII in periodontal ligament.
abstract: OBJECTIVE
  It is known that excessive mechanical force exerted by hyperocclusion induces occlusal trauma. However, the mechanism of the process remains unclear. In the present study, we employed an in vivo hyperocclusion rodent model to examine morphological and biological mechanisms of occlusal trauma in periodontal ligament tissue.
  
  
  METHODS
  To investigate alveolar bone resorption, tooth sections were stained to detect osteoclasts. To investigate the relationship between hyperocclusion and the regeneration of the cell matrix, we examined the effect of hyperocclusal force on the expression of collagens using immunohistochemistry and quantitative PCR methods.
  
  
  RESULTS
  The arrangement of collagen fibers in the furcation area of the teeth was undisturbed before hyperocclusion (control). Type I collagen was localized in the extracellular area at the furcation and there was faint expression and localization of type XII collagen in the periodontal ligament. The number of osteoclasts significantly increased in the furcation and lingual cervical regions on day 4 after hyperocclusion was induced. Type XII collagens were gradually up-regulated following the induction of hyperocclusion, in a time-dependent manner. Although type I collagen mRNA expression was stable before and after hyperocclusion, type XII collagen mRNA was significantly up-regulated on day 2 and day 4 after hyperocclusion treatment.
  
  
  CONCLUSIONS
  Our findings indicate that hyperocclusal force predominantly up-regulates the expression of type XII collagen in periodontal tissue, but not type I collagen, suggesting that there is a mechanism for regeneration of periodontal tissues as a response to occlusal trauma.
authors.affiliation: Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka 8140193, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuzuki
authors.affiliation: Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka 8140193, Japan. Electronic address: kajiya@college.fdcnet.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kajiya
authors.affiliation: Department of Dental Hygiene, Fukuoka College of Health Sciences, Fukuoka 8140193, Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: T-Goto
authors.affiliation: Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka 8140193, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsutsumi
authors.affiliation: Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka 8140193, Japan.
authors.forename: Tetsuomi
authors.initials: T
authors.lastname: Nemoto
authors.affiliation: Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka 8140193, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Okabe
authors.affiliation: Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka 8140193, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
mesh_terms: D016301:Alveolar Bone Loss / Q000473:pathology; D000818:Animals; D001696:Biomechanical Phenomena; D001732:Bite Force; D003094:Collagen / Q000096:biosynthesis; D024042:Collagen Type I / Q000378:metabolism; D024082:Collagen Type XII / Q000096:biosynthesis*; D003766:Dental Occlusion; D024021:Fibril-Associated Collagens / Q000096:biosynthesis; D024022:Fibrillar Collagens / Q000096:biosynthesis; D051379:Mice; D010010:Osteoclasts / Q000378:metabolism; D010513:Periodontal Ligament / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015854:Up-Regulation
chemical_list: D024042:Collagen Type I; D024082:Collagen Type XII; D024021:Fibril-Associated Collagens; D024022:Fibrillar Collagens; D003094:Collagen
keywords: Furcation; Hyperocclusion; Mechanical stress; Occlusal trauma; Periodontal ligament cells; Type XII collagen