title: Electron microscopic study on bone formation and bioresorption after implantation of beta-tricalcium phosphate in rabbit models.
abstract: BACKGROUND
  The role of bone formation and bioresorption in an early stage after implantation of beta-tricalcium phosphate (beta-TCP) was investigated using scanning and transmission electron microscopy (SEM, TEM).
  
  
  METHODS
  The ceramic beta-TCP cylinders were implanted into cavities drilled in the femoral condyles of eight NZW rabbits. Four of the rabbits were sacrificed at 2 weeks and four at 4 weeks after implantation, respectively. The femoral condyles were excised to prepare the specimens for SEM and TEM.
  
  
  RESULTS
  SEM showed giant cells of more than 20 mum in diameter were observed on the surface of beta-TCP at 2 weeks after implantation. TEM demonstrated that collagen fibrils secreted from the monocytic cells invaded beta-TCP micropores at 2 weeks. Multinucleated giant cells (MNGCs) were in contact with the surface of beta-TCP at 2 weeks. Some of them had a ruffled border (RB) at the cell-substrate interface, characteristic of osteoclasts.
  
  
  CONCLUSIONS
  These findings suggest that cell-mediated disintegration by osteoclasts played a role in the bioresorption of beta-TCP at an early stage after implantation. In addition, the micropores of beta-TCP ceramic may provide an environment for collagen formation, leading to the deposition of apatite crystals. Therefore, the micropores facilitate bone ingrowth as well as ceramic resorption.
authors.affiliation: Department of Orthopaedic Surgery, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Chazono
authors.forename: Takaaki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Kitasato
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Keishi
authors.initials: K
authors.lastname: Marumo
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D001672:Biocompatible Materials / Q000493:pharmacokinetics*; D001862:Bone Resorption; D002130:Calcium Phosphates / Q000494:pharmacology*; D005269:Femur / Q000648:ultrastructure*; D010012:Osteogenesis; D011817:Rabbits
chemical_list: D001672:Biocompatible Materials; D002130:Calcium Phosphates; C485817:beta-tricalcium phosphate