title: Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: bonding to titanium and scanning electron microscopy.
abstract: OBJECTIVE
  Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) production has been characterised and optimised by the sol-gel method and the dissolution and biological properties of these materials were investigated. It was the objective of this study to investigate the potential bond strength and interaction of these materials with titanium.
  
  
  METHODS
  HA, FHA and FA were synthesised by a sol-gel method. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the FHA and FA sol-gels. Using a spin coating technique the sol-gels were coated onto commercially pure titanium disks and crystallised at various temperatures. Using scanning electron microscopy (SEM) and elemental analysis, the surface characteristics, coating thickness and interaction of the Ti substrate and coating were investigated. The bond strengths of the coating to the Ti were investigated using an Instron Universal Load Testing Machine. Statistical analysis was performed with a two-way analysis of variance and post hoc testing with a Bonferroni correction.
  
  
  RESULTS
  (1) Coating speed inversely influenced the coating thickness. (2) Increasing fluoride ion substitution and heating temperature significantly increased bond strength and (3) increasing fluoride ion substitution increased the coating thickness.
  
  
  CONCLUSIONS
  FHA and FA synthesised using the sol-gel technique may offer a superior alternative to coating titanium implants with HA and plasma spraying. HA, FHA and FA materials synthesised by the sol-gel method may also have a use as bone grafting materials.
authors.affiliation: Peninsula Dental School, Plymouth University Peninsula Schools of Medicine and Dentistry, The John Bull Building, Tamar Science Park, Research Way, Plymouth, PL6 8BU, United Kingdom.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Tredwin
authors.forename: George
authors.initials: G
authors.lastname: Georgiou
authors.forename: Hae-Won
authors.initials: HW
authors.lastname: Kim
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Knowles
mesh_terms: D000704:Analysis of Variance; D001031:Apatites / Q000138:chemical synthesis*; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis*; D001840:Dental Bonding / Q000379:methods*; D005782:Gels / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D033081:Shear Strength; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D001031:Apatites; D020099:Coated Materials, Biocompatible; D005782:Gels; D014025:Titanium