title: Expression of osteoprotegerin and receptor activator of nuclear factor κB ligand in root resorption induced by heavy force in rats.
abstract: OBJECTIVE
  The aim of this study was to investigate the expression patterns of osteoprotegerin (OPG) and the receptor activator of nuclear factor κB ligand (RANKL) in root resorption during orthodontic tooth movement.
  
  
  METHODS
  Forty 12-week-old male SD rats were used with the right maxillary side as the experimental group and the left maxillary side as the control group. After 1 N (100g) force was loaded on the right maxillary first molar, the rats were sacrificed on days 0, 1, 4, 8, and 12. Mesial root resorption of the first molar, the number of odontoclasts and osteoclasts, and OPG and RANKL mRNA expression were determined by hematoxylin-eosin and scanning electron microscopy, tartrate-resistant acid phosphate staining, and in situ hybridization, respectively.
  
  
  RESULTS
  Serious root resorption was apparent on the pressure side of the mesial root of the right maxillary first molar on days 8 and 12. The number of odontoclasts in the cementum lacuna was elevated on days 8 and 12. OPG expression rose significantly on the tensile side, while RANKL expression increased on the pressure side. The mRNA level of RANKL was significantly elevated on days 4, 8, and 12. Moreover, the RANKL/OPG mRNA ratio was increased on the pressure side, but decreased on the tensile side.
  
  
  CONCLUSIONS
  Changes in the expression of RANKL mRNA and the RANKL/OPG mRNA ratio are accompanied by a parallel alteration in the number of odontoclasts and tooth resorption, suggesting crucial involvement of RANKL and OPG in tooth resorption.
authors.affiliation: Department of Orthodontics, The Affiliated Hospital of Stomatology, Chongqing Medical University, NO.7 Shangqingsi Road, Yuzhong District, 400015, Chongqing, China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Zhou
authors.forename: Gang
authors.initials: G
authors.lastname: Feng
authors.forename: Wenwen
authors.initials: W
authors.lastname: Zhou
authors.forename: Aishu
authors.initials: A
authors.lastname: Ren
authors.forename: Yang
authors.initials: Y
authors.lastname: Wu
authors.forename: Dingming
authors.initials: D
authors.lastname: Zhang
authors.forename: Hongwei
authors.initials: H
authors.lastname: Dai
mesh_terms: D000818:Animals; D001732:Bite Force; D001862:Bone Resorption / Q000209:etiology* / Q000503:physiopathology*; D008297:Male; D053244:Osteoprotegerin / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism*; D051381:Rats; D014087:Tooth Movement Techniques / Q000009:adverse effects*; D014092:Tooth Root / Q000473:pathology / Q000503:physiopathology*; D016896:Treatment Outcome
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand