title: Assessment of the suitability of a new brushite calcium phosphate cement for cranioplasty - an experimental study in sheep.
abstract: BACKGROUND
  Aim of this experimental study was to assess the suitability of a new brushite calcium phosphate cement (chronOS Inject) for cranioplasty and to compare the results with a commercially available apatite calcium phosphate bone cement (Biobon).
  
  
  METHODS
  A bilateral full-size craniotomy defect (23 mm in diameter) was created in the parietal bones of 18 adult Swiss Alpine sheep and filled with either chronOS Inject or Biobon. The observation intervals were 2, 4 and 6 months. Macroscopical, radiological, histological and histomorphometrical evaluations were performed.
  
  
  RESULTS
  New bone formation was moderate and did not differ significantly between the biomaterials. Cement resorption occurred centripetally in the chronOS Inject group and proceeded significantly faster than the degradation process of Biobon. However, implantation of chronOS Inject was associated with a significantly higher rate of fibrous tissue formation. Cement resorption was mediated by macrophages in the chronOS Inject group, while osteoclasts were the predominant cell type involved in degradation of Biobon. Osteoblasts were found adjacent to residual cement in both groups.
  
  
  CONCLUSIONS
  chronOS Inject demonstrated osteoconductive properties, good biocompatibility and superior bioresorbability but none of the cements proved suitable for filling large cranial bony defects due to the high rate of fibrous tissue formation and insufficient bony regeneration.
authors.affiliation: Musculoskeletal Research Unit, Faculty of Veterinary Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Jan Michael
authors.initials: JM
authors.lastname: Kuemmerle
authors.forename: Andrea
authors.initials: A
authors.lastname: Oberle
authors.forename: Christian
authors.initials: C
authors.lastname: Oechslin
authors.forename: Marc
authors.initials: M
authors.lastname: Bohner
authors.forename: Christian
authors.initials: C
authors.lastname: Frei
authors.forename: Ilka
authors.initials: I
authors.lastname: Boecken
authors.forename: Brigitte
authors.initials: B
authors.lastname: von Rechenberg
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001031:Apatites / Q000627:therapeutic use; D001843:Bone Cements / Q000627:therapeutic use*; D001861:Bone Regeneration / Q000187:drug effects; D018786:Bone Substitutes / Q000627:therapeutic use*; D002130:Calcium Phosphates / Q000737:chemistry / Q000627:therapeutic use*; D003399:Craniotomy / Q000379:methods*; D005260:Female; D012756:Sheep; D012886:Skull / Q000601:surgery
chemical_list: D001031:Apatites; D001843:Bone Cements; D018786:Bone Substitutes; D002130:Calcium Phosphates; C020243:calcium phosphate; C494366:calcium phosphate, dibasic, dihydrate