title: Evaluation of moldable, in situ hardening calcium phosphate bone graft substitutes.
abstract: OBJECTIVE
  Moldable in situ self-stabilizing and hardening bone graft materials facilitate handling and may be suitable for membrane-free bone regeneration methods. This study aimed to compare two moldable synthetic calcium phosphate materials in a rabbit calvarial defect model.
  
  
  METHODS
  In 12 New Zealand white rabbits, four evenly distributed 6 mm diameter defects were drilled in the calvarial bone. Three filler materials were randomly applied to 48 defects: an in situ hardening polylactide-coated ß-tricalcium phosphate (TCP), an in situ hardening polylactide-coated biphasic calcium phosphate (BCP), and a granular deproteinized bovine bone matrix (DBBM, positive control). One defect remained untreated and served as a negative control. Six animals were sacrificed after 4 weeks, and the remaining animals were sacrificed after 16 weeks. Biocompatibility, bone graft substitute integration and resorption, bone formation, defect bridging, and height of reconstructed hard tissue were assessed histologically and histomorphometrically.
  
  
  RESULTS
  All tested materials showed good biocompatibility. Semi-quantitative analysis and pair-wise comparison suggested that BCP was more efficient in centripetal bone formation when compared with TCP. After 4 weeks, significantly more bone had formed in the defects treated with either TCP or BCP materials compared with the untreated sites. BCP and DBBM did not show macroscopic signs of degradation, whereas the TCP material was partially resorbed after 16 weeks. Otherwise, no major differences were detected between the three materials.
  
  
  CONCLUSIONS
  The moldable, synthetic calcium phosphates are safe and suitable bone graft substitutes with outcomes that are comparable to the control material.
authors.affiliation: Clinic of Preventive Dentistry, Periodontology and Cariology, Center of Dental Medicine, University of Zürich, Zürich, Switzerland.
authors.forename: P R
authors.initials: PR
authors.lastname: Schmidlin
authors.forename: F
authors.initials: F
authors.lastname: Nicholls
authors.forename: A
authors.initials: A
authors.lastname: Kruse
authors.forename: R A
authors.initials: RA
authors.lastname: Zwahlen
authors.forename: F E
authors.initials: FE
authors.lastname: Weber
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001861:Bone Regeneration / Q000187:drug effects*; D018786:Bone Substitutes / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry; D005260:Female; D006882:Hydroxyapatites / Q000737:chemistry; D016348:Osseointegration; D011817:Rabbits; D011897:Random Allocation; D012886:Skull / Q000601:surgery
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D002130:Calcium Phosphates; D006882:Hydroxyapatites; C074950:hydroxyapatite-beta tricalcium phosphate; C020243:calcium phosphate