|dc.identifier.citation||Chen, X. 2015. Novel Halide Containing Bioactive Glasses. Queen Mary University of London||en_US
|dc.description.abstract||Bioactive glasses (BG) are widely used in dentistry and medicine due to the ability to
form a hydroxyapatite layer to bond to bone. Fluoride has been introduced into BG to
provide additional effects, such as inhibition at enamel and dentine demineralisation,
reduction of glass melting temperature and facilitating an acid durable fluorapatite
formation etc.. Therefore, fluoride containing BG are attractive for remineralising
toothpaste application. However, excessive fluoride is problematic.
Chlorine is thought to behave like fluorine in terms of glass structure and properties.
As the chloride ion is larger than fluoride ion, the incorporation of chloride could
expand the glass volume that might result in a more open structure and a more
degradable glass. These glasses are of interest for resorbable bone grafts and
remineralising toothpastes. In this thesis, the investigation of chloride as an alternative
to fluoride in the silicate BG was carried out for the first time.
Sodium free BG based on SiO2-P2O5-CaO-CaF2/CaCl2 or SiO2-CaO-CaF2/CaCl2 with
varying calcium halide content were synthesised via a melt-derived route and
characterised by various advanced techniques. The glass bioactivity was estimated in
Tris and SBF. Ion release measurements were carried out by using ICP-OES and ion
selective electrodes. The apatite formation was characterised by FTIR, XRD and MASNMR.
The crystallisation events of the glasses were explored by heat treatment.
This study reveals that the majority of chloride is successfully retained in the Q2 type
silicate BG. Glass transition temperature and density decrease with increasing halide
content. The studied high phosphate containing BG are highly dissolvable and formed
apatite-like phases within 3h in Tris. The glass dissolution rate was found to increase
with CaCl2 content but not with CaF2. On heat treatment, fluorapatite or chlorapatite is
the main crystalline phase in phosphate containing glasses, while CaF2/CaCl2 is likely
the one for the glasses without phosphate. This is the first time to our knowledge that
chlorapatite has been shown to crystallise from a glass.||
|dc.description.sponsorship||DAAD - German Academic Exchange Service||en_US
|dc.publisher||Queen Mary University of London||en_US
|dc.title||Novel Halide Containing Bioactive Glasses||en_US
|dc.rights.holder||The copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the author||