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Title: Calcium phosphate nanoparticles for potential application as dental remineralising agent
Author: Mok, Zi
ISNI:       0000 0004 9357 6825
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2020
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The excellent biocompatibility of calcium phosphate has allowed multiple applications within the human body. One of them is to replace the hydroxyapatite lost in the enamel due to dental decay or erosion. Nanosized calcium phosphate particles could potentially fill the nanoporous surface of a carious or cavitated tooth and be useful as a remineralising treatment. Here the aims were to synthesise and characterise calcium phosphate nanoparticles (CPNPs), to prepare and optimise hydroxyapatite (HA) disc as a suitable alternative substrate model to the enamel, and to investigate the remineralisation properties of CPNPs on the HA disc. A preparation of CPNPs made via co-precipitation of calcium chloride and sodium phosphate with magnetic stirring was described, and sodium citrate used as the capping agent. The effects of the concentration of the capping agent, pH and temperature on the particle size were examined with dynamic light scattering. The particle size was also confirmed with nanoparticle tracking analysis, scanning electron microscopy (SEM), transmission electron microscopy and atomic force microscopy. The crystallinity of CPNPs was assessed with Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction, whilst the calcium to phosphorus ratio was investigated with inductively coupled plasma mass spectroscopy and optical emission spectroscopy, and total reflection X-ray fluorescence spectroscopy. It was demonstrated that colloidally stable CPNPs of different nanoparticle size range as small as 30 nm, with high HA crystallinity and a small degree of amorphousness had been produced. Next, HA disc was etched in an unstirred 0.5 M acetate buffer (pH 4.0) at room temperature at various timepoints, to produce a suitably eroded substrate for remineralisation by comparing it with the enamel. An etching duration of 2 h on the HA disc, assessed by SEM, Knoop microhardness, and surface roughness and step height measured by a 3profilometer was deemed suitable to be used as the first demineralised artificial substrate model for remineralisation. Then, the remineralisation approaches and factors affecting remineralisation were identified, which involve the duration of exposure to CPNPs, agitated or stagnant exposure to CPNPs, with or without artificial saliva, time gap in between etching and exposure to CPNPs, and citrate concentration and pH of the formulation of CPNPs. It was established that CPNPs were heterogeneously deposited on the HA disc. The next phase of work will be to improve the adherence and penetration of CPNPs into the core of HA disc.
Supervisor: Thanou, Maria ; Proctor, Gordon Burgess ; Thompson, Van Purdy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available