title: [Expression of receptor activator of nuclear factor kappaB ligand and osteoprotegerin in chronic apical periodontitis].
abstract: OBJECTIVE
  To investigate the expression of key mediators that regulate bone resorption, receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in human periapical granuloma (PG) and radicular cyst (RC) characterized by periapical bone destruction.
  
  
  METHODS
  Immunohistochemical technique was performed using monoclonal antibody to detect RANKL and OPG expression in PG (n= 20 ) and RC (n= 20 ). As control group, healthy periodontal ligament tissues (n = 6 ) were obtained from teeth with orthodontic indication of extraction.
  
  
  RESULTS
  The RANKL protein expression was significantly higher in PG (43.74 +/- 8.40) and RC (40.33 +/- 7.53) than in control group (15.47 +/- 2.59, P=0.000) , but no statistical significance could be found between PG and RC groups(P=0.161) .The expression of OPG in PG (27.81 +/- 5.17), RC (26.35 +/- 3.86) and control group (24.33 +/- 3.50) show no statistical significance (P >0.05). Moreover, RANKL/OPG ratio in PG (1.59 +/- 0.26) and RC (1.54 +/- 0.24) was much higher than that in control group (0.64 +/- 0.10, P=0.000), however the ratio of RANKL/OPG showed no significant difference between PG and RC groups (P= 0.504) .
  
  
  CONCLUSIONS
  RANKL and OPG were observed in the periapical lesions. RANKL may be responsible for bone resorption in periapical lesions. RANKL and OPG may play an important role in the development of periapical lesions.
authors.affiliation: Department of Special Dentistry, Peking Univesity School and Hospital of Stomatology, Beijng 100081, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Fan
authors.forename: Cheng-Fei
authors.initials: CF
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
mesh_terms: D002908:Chronic Disease; D006801:Humans; D053244:Osteoprotegerin / Q000378:metabolism*; D010485:Periapical Periodontitis / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism*
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human