Influence of fluorine in the synthesis of apatites. Synthesis of solid solutions of hydroxy-fluorapatite

• Published in: Biomaterials Vol. 24; no. 21; pp. 3777 - 3785
• Main Authors: Rodrı́guez-Lorenzo, L.M, Hart, J.N, Gross, K.A
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.09.2003
• Subjects: Apatites - chemistry; Bioceramics; Biocompatible Materials; Ceramics - chemistry; Fluorapatite; Fluorine - pharmacology; Hydroxy-fluorapatite; Hydroxyapatites - chemistry; Kinetics; Microscopy, Electron; Powders - chemistry; Solid solutions; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared; Synthesis; Temperature; X-Ray Diffraction; X-Rays; Bioceramics; Hydroxy-fluorapatite; Synthesis; Solid solutions; Fluorapatite
• ISSN: 0142-9612; 1878-5905
• DOI: 10.1016/S0142-9612(03)00259-X

Hydroxy-fluorapatites (OH-FAps) occur biologically in teeth and form the basis for application as biomaterials. This work aims to synthesize a series of fluoride substituted calcium hydroxyapatites (OHAps) to determine how fluoride influences the synthesis and the resulting characteristics of solid solutions. OH-FAPs powders were synthesized with a chemical composition of Ca 10(PO 4) 6(OH) 2− x F x , with x=0.0, 0.4, 0.8, 1.2, 1.6 and 2.0. The synthesis of partially substituted OHAp yields materials with lower crystallinity and higher specific surface area than OHAp or fluorapatite (FAp). The smallest crystal size of 263 Å, occurs at less than 50% hydroxyl substitution with fluoride at x=0.4, and the highest surface area of 132 m 2/g occurs at x=0.8. Reaction kinetics occur faster at higher fluoride content, producing the expected Ca/P ratio of 1.67 only for x=2.0. X-ray and IR studies show that OH-FAPs are homogeneous solid solutions instead of mixtures of OHAp and FAp. The presence of a high fluoride concentration increases the driving force for crystal growth during the calcination process.