title: Substituted hydroxyapatites for bone regeneration: A review of current trends.
abstract: At present hydroxyapatite (HA) is been extensively investigated for biomedical applications, largely as a result of its similarity in composition to the mineral portion of bone. Although HA undergoes osseointegration and is bioactive and osteoconductive, the inherent brittleness and low fracture toughness limits its use under load bearing conditions, also once implanted in the body, HA takes a long time to resorb. The crystal structure of HA is conducive to a variety of ionic substitutions. To accurately mimic the calcium deficient and carbonate-containing nature of HA in bone, both cationic and anionic substituents have been incorporated to synthetic HA. This article focuses on the incorporation of both the well established (Zn, Si, Sr, F, and carbonate) and latest ions (Ag, citrate, iron, niobate, and tantalates) into the HA structure and aims to highlight the key effects of these substitutions in terms of their chemical, physical, and biological properties. It can be shown that a minor substituent cannot only alter the microstructure, stability and crystallinity of the HA structure in an implant, but also have a significant effect on bone cells colonizing the implant, which in turn can influence the new bone formation and bone remodeling processes. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1285-1299, 2017.
authors.affiliation: Department of Anatomy, School of Medical Sciences, University of Otago, Dunedin, 9054, New Zealand.
authors.forename: Jithendra T B
authors.initials: JTB
authors.lastname: Ratnayake
authors.affiliation: Chemistry Department, School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand.
authors.forename: Michael
authors.initials: M
authors.lastname: Mucalo
authors.affiliation: Department of Anatomy, School of Medical Sciences, University of Otago, Dunedin, 9054, New Zealand.
authors.forename: George J
authors.initials: GJ
authors.lastname: Dias
mesh_terms: D000818:Animals; D001861:Bone Regeneration / Q000187:drug effects*; D018786:Bone Substitutes / Q000737:chemistry / Q000627:therapeutic use; D017886:Durapatite / Q000737:chemistry / Q000627:therapeutic use; D006801:Humans; D016348:Osseointegration / Q000187:drug effects*
chemical_list: D018786:Bone Substitutes; D017886:Durapatite
keywords: bone and bone grafts; calcium phosphates; hydroxyapatite; ionic substitutions