title: Effects of long-term occlusal hypofunction and its recovery on the morphogenesis of molar roots and the periodontium in rats.
abstract: OBJECTIVE
  To investigate the effects of long-term, artificially created, hypofunctional occlusion and its recovery on the morphology of rat molar roots.
  
  
  METHODS
  Eighteen 5-week-old Wistar-strain male rats were randomly divided according to their periodontal conditions into normal, hypofunctional, and recovery groups (n = 6 in each). In the experimental hypofunctional and recovery groups, a bite-raising appliance was set to produce hypofunction at the molar region. All groups were analyzed at 16 weeks of age using three-dimensional micro-computed tomography. Root length, width, and area as well as the thickness and the area of the periodontal ligament (PDL) space of the maxillary first molar were calculated.
  
  
  RESULTS
  Roots were longer and narrower in the hypofunctional group than in the control group. The mesial root in particular showed a dramatic change. Root area also decreased significantly in the hypofunctional group compared to the other groups. Moreover, the PDL thickness and area decreased significantly in the hypofunctional group compared to the control group, but increased in the recovery group compared to the hypofunctional group.
  
  
  CONCLUSIONS
  These findings suggest that root size and PDL structure may be reduced due to disuse atrophy resulting from a defect in occlusal function, but may be recovered following a gain of occlusal stimuli.
authors.affiliation: Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan. motumo@hiroshima-u.ac.jp
authors.forename: Masahide
authors.initials: M
authors.lastname: Motokawa
authors.forename: Akiko
authors.initials: A
authors.lastname: Terao
authors.forename: Ersan I
authors.initials: EI
authors.lastname: Karadeniz
authors.forename: Masato
authors.initials: M
authors.lastname: Kaku
authors.forename: Toshitsugu
authors.initials: T
authors.lastname: Kawata
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Carmen
authors.initials: C
authors.lastname: Gonzales
authors.forename: M Ali
authors.initials: MA
authors.lastname: Darendeliler
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tanne
mesh_terms: D019412:Anatomy, Cross-Sectional; D000818:Animals; D002508:Cephalometry / Q000379:methods; D003766:Dental Occlusion; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008310:Malocclusion / Q000503:physiopathology* / Q000628:therapy; D008963:Molar / Q000000981:diagnostic imaging / Q000254:growth & development*; D009024:Morphogenesis / Q000502:physiology*; D009811:Odontometry / Q000379:methods; D009967:Orthodontic Appliances; D010513:Periodontal Ligament / Q000000981:diagnostic imaging / Q000254:growth & development*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function / Q000502:physiology; D013997:Time Factors; D014092:Tooth Root / Q000000981:diagnostic imaging / Q000254:growth & development*; D055114:X-Ray Microtomography / Q000379:methods