Quantitative Determination of Lattice Fluoride Effects on the Solubility and Crystallinity of Carbonated Apatites with Incorporated Fluoride

Abstract

The purpose of this study was to evaluate quantitatively the effects of fluoride on the solubility and crystallinity of carbonated apatites (CAPs) after its incorporation into the crystal lattice using the metastable equilibrium solubility (MES) distribution method. Fluoride-incorporated CAPs (F-CAPs) of two different carbonate levels (3 and 5%) and fluoride contents from 0 to 20,000 µg/g were synthesized. X-ray diffraction experiments and Rietveld analysis were conducted to obtain crystallite microstrain and unit cell parameters. Acetate buffer MES solution media were prepared at two solution fluoride concentrations (0.2 and 2.0 mg/l) and at two pHs (5.0 and 5.7). The unit cell a-axis values of the F-CAPs were found to decrease as the fluoride content increased, consistent with the fluoride being incorporated into the crystal lattice. The fluoride concentrations in the MES solution media were high enough to provide a ‘swamping’ effect such that the fluoride released from the F-CAPs during dissolution was minimal in changing the solution fluoride concentration. Employing the MES distribution superposition method, it was shown that the surface complex possessing the fluorapatite (FAP) stoichiometry [Ca₁₀(PO₄)₆F₂] accounted for the MES distribution behavior of all experiments. In addition, the mean pI_FAP [the value of –log(a_Ca¹⁰a_PO_₄⁶a_F²) calculated from the ionic activity product based on FAP stoichiometry of the MES dissolution media in which 50% of the F-CAPs had dissolved] correlated well with the crystallite microstrain parameters of the F-CAPs. The incorporated fluoride in the F-CAPs showed only modest effects on F-CAP crystallinity and solubility.

Internalization of Fluoride in Hydroxyapatite Nanoparticles

“…IAP FAP in all fluoridated tests also stabilizes by 144 h. IAP FAP for the 30 mg-F/L tests plateaus more quickly after 10 h and drops slightly after 144 h, consistent with exhibiting FHAP solubility that decreases with increased F – as a fraction of X sites (or F – fraction). − Compared to a similarly high-solubility FAP, the solutions are slightly supersaturated and appear to be slowly converging toward that solubility. Therefore, the K s0 ’s of HAP and FAP from Zhu et al are appropriate reference points for the HAP in this study.…”

“…XRD of postfluoridated HAP did not indicate the presence of any phase other than apatite (Figure S4a). HAP and FAP share the same diffraction patterns except for peak shifts largely indicative of a change in unit cell size (Δ V / V = 1.3%) due to differences in the size and lattice position of F – and OH – ions. ,, This feature has been used to quantify F – incorporation in FHAP solid solutions where the a unit cell dimension decreases linearly with increased F – fraction while the c dimension remains relatively constant. ,, Using the Rietveld method, refined a and c parameters of fluoridated samples were plotted against F – fraction in Figure S4b. The a dimension decreased with increased F – fraction, while c did not change.…”

“…33,66,67 This feature has been used to quantify F − incorporation in FHAP solid solutions where the a unit cell dimension decreases linearly with increased F − fraction while the c dimension remains relatively constant. 65,68,69 Using the Rietveld method, refined a and c parameters of fluoridated samples were plotted against F − fraction in Figure S4b. The a dimension decreased with increased F − fraction, while c did not change.…”

Fluorapatite-Coated Percutaneous Devices Promote Wound Healing and Limit Epithelial Downgrowth at the Skin-Device Interface

“…Te apatite (HA, FHA, and FA) powders were manufactured in-house, in accordance with the methods previously described [18,19]. After synthesis, the powders were characterized using x-ray difraction (XRD), inductively coupled plasma-mass spectroscopy (ICP-MS), and Fourier-transform infrared spectroscopy (FTIR) to confrm the apatite structure [14].…”

Bone histology reveals the first record of titanosaur (Dinosauria: Sauropoda) from the Late Cretaceous of Bulgaria

“…The process of fluoridisation imposes changes in the apatite structure, expressed by decreasing apatite unit cell a-axis value with the increase of fluoride content. Apart from the shortening along a-axis, it was reported that fluoride incorporation into the carbonate-and xydroxylapatite mineral lattice increases the mineral crystallinity in the direction of the longest caxis of the crystallite, the amount of crystallographic microstrain, the solubility and the optical birefringence (Qiao et al, 2017;Wopenka and Pasteris, 2005;Yan et al, 2013).…”