title: Time-dependent changes in fresh-frozen bone block grafts: tomographic, histologic, and histomorphometric findings.
abstract: BACKGROUND
  Bone allografts have shown satisfactory clinical results in alveolar ridge reconstructions. However, the process of incorporation and the resorption rates of these grafts are not yet fully understood.
  
  
  OBJECTIVE
  The aim of this study was to use computed tomography (CT), histology, and histomorphometry to assess the time-dependent rates of resorption and incorporation of fresh-frozen bone allografts.
  
  
  METHODS
  Twenty-four patients underwent alveolar ridge reconstruction with bone block allografts and were randomly allocated to three groups with different graft healing periods (4, 6, or 8 months) before implant placement. To assess the resorption rates, CT scans were acquired within 7 days after bone graft surgery and at the end of the period. Graft samples were collected and sent for histological and histomorphometric analyses.
  
  
  RESULTS
  The graft resorption mean rates were 50.78% ± 10.43, 32.77% ± 7.84, and 13.02% ± 3.86 for the 4-, 6-, and 8-month groups, respectively, and were significantly different among the three groups. Newly formed bone with osteocytes near the grafted bone was observed in all three groups. The number of osteocytes was significantly lower at 4 months. Grafted bone remains were significantly higher in the shortest period of time. All of the grafts showed large amounts of calcified tissue.
  
  
  CONCLUSIONS
  All three groups showed new bone formation and different bone resorption rates. Graft healing periods of 4 months showed less graft resorption and seemed to be the most favorable for implant placement. Healing periods of 8 months showed the largest rate of graft resorption, which could render the grafts unfavorable for implant placement.
authors.affiliation: Department of Periodontology, UERJ - Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Daniel
authors.initials: D
authors.lastname: Deluiz
authors.forename: Luciano Santos
authors.initials: LS
authors.lastname: Oliveira
authors.forename: Fábio Ramôa
authors.initials: FR
authors.lastname: Pires
authors.forename: Eduardo Muniz Barretto
authors.initials: EM
authors.lastname: Tinoco
mesh_terms: D000368:Aged; D064591:Allografts; D000540:Alveolar Ridge Augmentation / Q000379:methods*; D001706:Biopsy; D001862:Bone Resorption / Q000000981:diagnostic imaging*; D016025:Bone Transplantation / Q000379:methods*; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D016896:Treatment Outcome
keywords: allograft; alveolar ridge reconstruction; atrophic maxilla; bone grafting