title: Age-related and surgically induced estrogen deficiencies may differently affect bone around titanium implants in rats.
abstract: BACKGROUND
  Valuable information has been obtained using the ovariectomy model; however, clinical studies have indicated that such a model may not be appropriate to parallel with the postmenopausal condition and titanium implants. Thus, this study aimed to comparatively evaluate, by histometric analysis, the influence of age-related (ARED) and surgically induced (OVX) estrogen deficiencies on bone around titanium implants inserted in rats.
  
  
  METHODS
  Single screw-shaped titanium implants were placed in rat tibiae and animals were then assigned to one of the following groups: SHAM (N = 15): bilateral sham ovariectomies in 90-day-old rats, 21 days before implant placement; OVX (N = 15): bilateral ovariectomies in 90-day-old rats, 21 days before implant placement; and ARED (N = 15): implant placement in reproductive aged rats (22 months old). After 60 days, the animals were sacrificed and undecalcified sections obtained. Bone-to-implant contact (BIC) and bone area (BA) within the limits of implant threads and bone density (BD) in a 500 microm-wide zone lateral to the implant were obtained and arranged for cortical (zone A) and cancellous (zone B) bone regions.
  
  
  RESULTS
  For zone A, intergroup analysis showed no significant differences regarding BIC and BA (P >0.05). In contrast, ARED negatively influenced BD around the implants (P <0.05). In zone B, OVX negatively affected BIC and BA (P <0.05), and both ARED and OVX groups demonstrated lower BD than the SHAM group (P <0.05).
  
  
  CONCLUSIONS
  Within the limits of this study, it can be concluded that ARED mainly affects preexisting bone while OVX more significantly affects both newly formed and preexisting bone.
authors.affiliation: Department of Prosthodontics and Periodontics, Division of Periodontics, School of Dentistry at Piracicaba, University of Campinas, Piracicaba, São Paulo, Brazil.
authors.forename: Poliana Mendes
authors.initials: PM
authors.lastname: Duarte
authors.forename: Patrícia Furtado
authors.initials: PF
authors.lastname: Gonçalves
authors.forename: Márcio Zaffalon
authors.initials: MZ
authors.lastname: Casati
authors.forename: Enilson Antonio
authors.initials: EA
authors.lastname: Sallum
authors.forename: Francisco H
authors.initials: FH
authors.lastname: Nociti
mesh_terms: D000367:Age Factors; D000469:Alkaline Phosphatase / Q000097:blood; D000818:Animals; D015519:Bone Density; D001842:Bone and Bones / Q000503:physiopathology*; D015921:Dental Implants; D004967:Estrogens / Q000172:deficiency*; D005260:Female; D016348:Osseointegration; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar; D014025:Titanium
chemical_list: D015921:Dental Implants; D004967:Estrogens; D014025:Titanium; D000469:Alkaline Phosphatase