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Title: Introduction and development of aluminium ion free silicate based bioactive glass ionomer cement based on glass flakes and setting modifier (citrate) for direct posterior dental restorations
Author: Uddin, Muhammad Khawaja Hammad
ISNI:       0000 0004 7660 6463
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Enhanced glass ionomer cement (GIC), based on bioactive glasses, are relatively new material used in minimally invasive prevention of dental caries in the field of restorative dentistry over the past few decades. A series of aluminum ion free silicate based bioactive glasses with the substitution of calcium with strontium and barium with the admixture of poly-acrylic acid after the introduction of tartrate and citrate ions in the presence of water were produced to study for dental applications. Aluminum ion free silica based bioactive glass composition substituting 3 mole percent of calcium oxide with strontium and barium 46.14 SiO2.2.60 P2O5.23.95 CaO.24.35 Na2O.1.5X1.1.5X2 (X1= SrO and SrF2) and (X2= BaO and BaF2) were synthesised using melt quenching technique. It was postulated that a change of particle size of filler content and introduction of citrate ions would enhance the mechanical, chemical and biological properties of the resultant set cement. To test this hypothesis, glass flakes of different sizes, ranging from 100 nm to 100 μm were obtained from Leeds Glass Flakes Company Ltd, UK and were characterised physically, mechanically and in vitro biologically. The analysis of prepared glass and cement samples as undertaken using various physical, chemical, thermal, mechanical and in vitro biological characterisation techniques: X-ray diffraction analysis (XRD), particle size analysis, contact angle and density measurements, Brunauer-Emmett-Teller analysis, FTIR and Raman spectroscopy, energy dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), differential thermal analysis, compression strength, Gilmore needle test, in-vitro bioactivity with stimulated body fluid study (SBF) and biocompatibility (MTT assay and confocal microscopy). The produced series of glasses were found to be amorphous in nature after x-ray diffraction analysis. Results of both contact angle and Brunauer-Emmett-Teller analysis revealed that calcium substitution with strontium and barium created positive change in terms of increased hydrophilicity and surface area. FTIR and Raman spectra of all glass samples (BG 1-7) revealed silicate and phosphate related peaks and thus, the presence of phospho-silicate structure. Characterisation of all ionomer cement samples with FTIR and Raman spectroscopy after the introduction of both tartaric and citric acid showed organic and inorganic peaks, endorsing the formation of resultant glass ionomer cement. Scanning electron micrographs indicated the layer formation over the surface of all prepared cement samples after 7th and 14th days in simulated body fluid solution. Similarly, the elemental analysis by energy dispersive x-ray spectroscopy revealed the presence of hydroxyl-carbonate apatite along with calcium phosphate ratio close to 1.67. The in vitro cell viability analysis for both glass and ionomer cement samples based on MTT assay and confocal study established the connection between improved biocompatibility after the substitution of strontium, barium and fluoride ions in glass and citrate ions in ionomer cement samples. Enhanced mechanical properties were also observed with further analysis of the resultant cement by compressive strength and Gilmore needle tests for the evaluation of working and setting time of all tartrate and citrate-based ionomer cements. On the basis of obtained results, it was concluded that calcium ions can be substituted with strontium and barium ions effectively due to their similarity in ionic radius and charge. These ions allow the creation of an extended and more freely cross-linked glass network without altering the fundamental glass structure. Moreover, substitution significantly increases the desired properties in terms of bioactivity, biocompatibility and mechanical characteristics of the developed glass series and resultant ionomer cements. Thus, the produced series of aluminium ions free silicate based bioactive glass series can be incorporated into existing glass ionomer cement systems for both medical and dental applications with beneficial results.
Supervisor: Rehman, Ihtesham Ur ; Hand, Russell J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available