title: Prevention of root resorption in hypofunctional teeth by occlusal function recovery.
abstract: OBJECTIVE
  To clarify whether occlusal hypofunction is one of the key determinants for root resorption during tooth movement and root resorption is prevented by its recovery.
  
  
  METHODS
  The rats were randomly divided into one control and two experimental groups: hypofunctional and recovery groups. In the hypofunctional group, an anterior metal cap and bite plate were attached to the maxillary and mandibular incisors to simulate occlusal hypofunction. In the recovery group, the appliances were removed 7 weeks after their use, and the rats were allowed to bite for 4 weeks after removal. At the age of 16 weeks, the upper first molars were moved and after 0, 7, 14, and 21 days, the maxillae were resected. The resorption area was quantified morphohistologically and tartrate-resistant acid phosphatase (TRAP)-positive cells on the root surface were counted. We also examined the expressions of receptor activator of nuclear factor-κB ligand (RANKL), macrophage-colony stimulating factor (M-CSF), and interleukin (IL)-8 immunohistochemically.
  
  
  RESULTS
  The amount of root resorption and the number of TRAP-positive cells were significantly greater in the hypofunctional group than in the control and recovery groups. Moreover, immunoreactivity for RANKL, M-CSF, and IL-8 was detected in the periodontal ligament and on the root surface in the hypofunctional group.
  
  
  CONCLUSIONS
  Occlusal hypofunction is one of the critical factors for root resorption; however, root resorption may be prevented by recovery of occlusal function.
authors.affiliation: a  Employee practitioner, Hiroshima, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Hayashi
authors.affiliation: b  Private practice, Hiroshima, Japan.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Hayashi
authors.affiliation: c  Professor and Chair, Department of Orthodontics, Kanagawa Dental University, Kanagawa, Japan.
authors.forename: Toshitsugu
authors.initials: T
authors.lastname: Kawata
mesh_terms: D000818:Animals; D003766:Dental Occlusion; D016209:Interleukin-8 / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D009967:Orthodontic Appliances; D010513:Periodontal Ligament / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D020127:Recovery of Function; D012391:Root Resorption / Q000517:prevention & control*; D014092:Tooth Root
chemical_list: D016209:Interleukin-8; D053245:RANK Ligand; D016173:Macrophage Colony-Stimulating Factor
keywords: Occlusal hypofunction; Root resorption