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Title: New reparative material for repairing failed tooth-restoration complex
Author: Al-Taee, Lamis Abdul Hameed
ISNI:       0000 0004 7963 9383
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2019
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Objectives: This research aimed to develop a novel reparative material based on resin-modified glass-ionomer cement (RMGIC) chemistry. Two objectives were pursued. Firstly, a systematic study evaluated the ISO properties of 8 commercially available GICs/RMGICs comparing the effect of auto and manual mixing. Secondly, combining the properties of ethylene glycol methacrylate phosphate (EGMP) monomer, a proton-conducting electrolyte with functional groups as an adhesion promoter in RMGICs was explored for its potential application as a reparative material for failed tooth-restoration complexes (TRCs). The reactive polar groups were expected to interact with the metallic cations during setting reactions of the cement and form complexes that might alter its physical properties. Based on this hypothesis a novel class of material with a dynamic interaction with the tooth tissue and restorative material via the inclusion of EGMP as a monomer in commercial RMGIC's were formulated and characterised. Materials and methods: In the first experiment, the physical properties of eight commercial restorative materials (Fuji IX GP Extra (C&H), KetacTM Fill Plus Applicap (C&H), Fuji II LC (C&H), Glass Carbomer Cement and Equia® Forte Fil), capsulated versus hand-mixed, were assessed and compared up to four weeks storage in artificial saliva at 37°C. The properties include the compressive strength (CS) and compressive modulus (CM), microhardness (MH), biaxial flexural strength (BFS), fluid uptake and fluoride ion release. In the second experiment, EGMP was incorporated at different proportions (10-40% by weight) to the liquid phase of the commercial RMGIC (Fuji II LC). Optimisation and chemical characterisation of the modified formulations were done to justify the best formulation with optimised physical and adhesion abilities to proceed with, as a step forward developing the new reparative material. The physical properties include working and setting time, CS and CM, MH, BFS, water uptake behaviour, fluoride ion release after different time intervals. Furthermore, the structural and chemical characterisations of the modified formulations were accomplished using FTIR and SEM-EDX analysis. The 30% by weight EGMP-RMGIC (pRMGIC) was selected for in vitro testing to evaluate the shear bond strength (SBS) after 24 h and 3 months' storage to different tooth surfaces (sound enamel, demineralised enamel, sound dentine and carious affected dentine (CAD)) and restorative interfaces (amalgam, composite, RMGIC and GIC). The results were compared to three different commercial restorative materials RMGIC (Fuji II LC), GIC (Fuji XI GP), and universal composite resin (Filtek™ Supreme). All comparisons were considered statistically significant if p < 0.05. Failure modes and SEM images were analysed. Results: The encapsulated systems showed superior performance than their equivalent manually-mixed cements due to no variation in powder/liquid ratio, the reduced porosity, uniform wetting of the powder particles during mixing and reduced operator-induced variability. The experimental EGMP-contained cements exhibited higher CS and CM, MH and a two-fold increase in the BFS compared to the control cement post-ageing. The microstructure exhibited an integrated structure that accounted for the increased stiffness and BFS with increasing the content of EGMP. The phosphate groups accounted for the hydrophilicity that it is beneficial in term of adhesion with tooth structure whilst the interaction with the matrix decreased the solubility and fluoride release. pRMGIC showed a robust and durable bond strength to different dental substrates (healthy and diseased). Ageing has no significant effect on further enhancement of the bond strength, except to sound dentine, however, there was a shift from adhesive to mixed/cohesive modes in most groups after three months' storage. This may indicate the potential of augmented chemical integrations of pRMGIC via the phosphate groups with the remaining tooth structure. pRMGIC can effectively repair the conditioned amalgam surfaces when used with adhesive. It demonstrated an effective repair strength to RMGIC and resin composite substrates after three months' storage whether applied with or without an adhesive. In GIC repair, the repair strength of pRMGIC was comparable to the control, however, the adhesion strength was higher than the cohesive strength of the substrate. Conclusion: This thesis demonstrates the successful inclusion of EGMP monomer into the RMGICs as an effective and innovative material, specifically as a reparative material for failing TRCs and also as a restorative-grade GIC. Results lay the foundation to develop further encapsulated system with the scope of incorporation of remineralising bioactive glasses.
Supervisor: Banerjee, Avijit ; Deb, Sanjukta ; Foxton, Richard Mark Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available