title: Ultrastructural comparison of hydroxyapatite and silicon-substituted hydroxyapatite for biomedical applications.
abstract: Silicon-substituted hydroxyapatite (Si-HA) has been shown to lead to significantly increased rates of bone apposition when compared with phase-pure hydroxyapatite (HA) bioceramic implants (Patel N, et al. J Mater Sci Mater Med 2002;13:1199-1206). However, uncertainty remains about the mechanism by which Si increases the in vivo bioactivity. In this study, defect structures in Si-HA were observed and characterized for the first time using high-resolution transmission electron microscopy. Using tilting experiments and the g. b = 0 criterion for invisibility, the Burgers vectors of dislocations in phase-pure HA and 0.8 wt % Si-HA were characterized to be screw and mixed in character. Dislocations were observed in both pure HA and 0.8 wt % Si-HA with no significant difference in dislocation density between HA and Si-HA. However, our findings suggest that an increased number of triple junctions in Si-HA may have a significant role in increasing the solubility of the material and the subsequent rate at which bone apposes Si-HA ceramics.
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom. aep30@cam.ac.uk
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Porter
authors.forename: Serena M
authors.initials: SM
authors.lastname: Best
authors.forename: William
authors.initials: W
authors.lastname: Bonfield
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D002516:Ceramics; D017886:Durapatite / Q000737:chemistry*; D008854:Microscopy, Electron; D019736:Prostheses and Implants; D012825:Silicon
chemical_list: D001672:Biocompatible Materials; D017886:Durapatite; D012825:Silicon