Layered Double Hydroxide for Long Term Delivery Of Fluoride
Date
2023-10-23
Authors
Journal Title
Journal ISSN
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Publisher
Saudi Digital Library
Abstract
Background
The prevention of early-stage carious lesions requires a continuous and controlled
release of fluoride in the oral environment, which is widely recognised. However,
dental caries continues to be a significant global health problem. Therefore, there
is a requirement for the development of a fluoride delivery system that can
consistently release fluoride at therapeutic levels. Layered double hydroxides
(LDHs) offer a promising solution to this challenge. LDHs have the capability to
absorb and release fluoride repeatedly, thus achieving the sustained therapeutic
release that will potentially enhance remineralisation.
Objective
Therefore, the aim of this study was to investigate the structure and fluoride
absorption and release capabilities of two types of LDH powders, namely 2:1
MgAl and ZnAl, after being charged with two different sodium fluoride
concentrations (1500 ppm and 5000 ppm) over two cycles, as well as to observe
the fluoride release over 7 days without charging.
Materials and Methods
The MgAl and ZnAl LDH powders with a divalent to trivalent ion ratio 2:1 were
successfully synthesised. These pristine LDH powders were characterised using
powder X-ray diffraction (pXRD), Fourier-transform infrared spectroscopy
(FTIR), and particle size analysis. Both LDH samples were charged with fluoride
solutions of different concentrations, 1500 ppm and 5000 ppm for 24 hours. The
fluoride absorption and release in deionised water from the LDHs over two cycles
5
(absorption, release, re-absorption, and re-release) and the 7 days were measured
using fluoride-ion selective electrode (ISE). Furthermore, the 2:1 MgAl and ZnAl
LDH powders after the charging and following the release process over two
cycles and 7 days were characterised using various techniques, including solid state 19F nuclear magnetic resonance NMR, FTIR, and pXRD.
Results
The LDH of both formulations 2:1 MgAl and ZnAl was largely maintain stable
after charging with 1500 and 5000ppm sodium fluoride solution. The 2:1 MgAl
LDH showed overall higher absorption and release of fluoride under all
conditions. The release from all the formulations continued even without
recharging for 7 days of study. The second cycle of fluoride release showed
higher concentration of fluoride concentration than was released in the first cycle
of release. The FTIR spectra of the charged LDH formulations and the samples
following the release showed higher intensity of carbonate in the structure
compared to the as-synthesised LDH. Solid-state 19F NMR showed diversity of
the fluorine environment in all types of LDH formulations, with the spectra of the
5000ppm charged samples exhibiting quite different spectra.
Conclusions
A novel finding emerged from the release results, demonstrating a significant
fluoride release from the LDHs over the 7 days, without any additional re-charge,
particularly with the 5000 ppm fluoride concentration. These findings hold
promise and open avenues for further research in the field of dental materials.
Description
Keywords
Layered double hydroxide Hydrotalcite Fluoride uptake Fluoride release