title: Comparison of in vivo dissolution processes in hydroxyapatite and silicon-substituted hydroxyapatite bioceramics.
abstract: The incorporation of silicate into hydroxyapatite (HA) has been shown to significantly increase the rate of bone apposition to HA bioceramic implants. However, uncertainty remains about the mechanism by which silicate increases the in vivo bioactivity of HA. In this study, high-resolution transmission electron microscopy was used to observe dissolution from HA, 0.8 wt% Si-HA and 1.5 wt% Si-HA implants after 6 and 12 weeks in vivo. Our observations confirmed that defects, in particular those involving grain boundaries, were the starting point of dissolution in vivo. Dissolution was observed to follow the order 1.5 wt% Si-HA>0.8 wt% Si-HA>pure HA and it was found to be particularly prevalent at grain boundaries and triple-junctions. These observations may help to explain the mechanism by which silicate ions increase the in vivo bioactivity of pure HA, and highlight the enhanced potential of these ceramics for biomedical applications.
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK. aep30@cam.ac.uk
authors.forename: A E
authors.initials: AE
authors.lastname: Porter
authors.forename: N
authors.initials: N
authors.lastname: Patel
authors.forename: J N
authors.initials: JN
authors.lastname: Skepper
authors.forename: S M
authors.initials: SM
authors.lastname: Best
authors.forename: W
authors.initials: W
authors.lastname: Bonfield
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism*; D018786:Bone Substitutes; D002516:Ceramics / Q000737:chemistry / Q000378:metabolism*; D005269:Femur / Q000378:metabolism / Q000473:pathology; D006882:Hydroxyapatites / Q000737:chemistry / Q000378:metabolism*; D020007:Implants, Experimental; D008422:Materials Testing; D008854:Microscopy, Electron; D011208:Powders / Q000737:chemistry; D012756:Sheep; D012825:Silicon / Q000737:chemistry / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D006882:Hydroxyapatites; D011208:Powders; D012825:Silicon