title: The effect of osteoprotegerin on implant osseointegration in ovariectomized rats.
abstract: BACKGROUND
  Osteoprotegerin (OPG), the endogenous inhibitor of RANKL, prevents or reverses bone loss in a variety of preclinical models of bone disease. Preclinical studies indicate that osteoporosis significantly impairs implant fixation. This study aims to investigate the role of OPG in implant osseointegration in ovariectomized rats.
  
  
  METHODS
  Twelve weeks after bilateral ovariectomy, each rat accepted two titanium screws in the proximal tibiae. All animals were then randomly divided into two groups: the control (10 rats) and OPG group (10 rats). Subcutaneous injection of OPG (10 mg/kg) or vehicle was performed three times a week. Eight weeks later, tibiae with screws were harvested for micro-computed tomography (μCT), histological and biomechanical analysis.
  
  
  RESULTS
  Compared to control, OPG increased the percent bone volume by 124%, the percent osseointegration by 167%, the mean trabecular number by 111%, the mean trabecular thickness by 92% (p< 0.01), the mean connective density by 95% (p< 0.05); and decreased the mean trabecular separation by 64% in μCT analysis (p< 0.05). Osteoprotegerin also increased bone area density by 160% and bone-to-implant contact by 234% in histomorphometric evaluation (p< 0.01), and increased the maximal push-out force by 228% in biomechanical test (p< 0.01).
  
  
  CONCLUSIONS
  Systemic administration of OPG improved implant osseointegration and fixation in ovariectomized rats, resulting from the increased peri-implant bone mass and improved trabecular microarchitecture.
authors.affiliation: State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Biao
authors.initials: B
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Xiliang
authors.initials: X
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Li
keywords: implant; osseointegration; osteoporosis; osteoprotegerin; rat