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Hybridisation of dental hard tissues with modified adhesive systems : therapeutic impact of bioactive silicate compounds on bonding to dentine

The first section of this work is a review of the literature necessary to understand the objectives of the project; it includes general information about dental adhesive technology as well as adhesion testing, about dentine hybridisation and about the drawbacks of contemporary bonding systems. Several studies revealed excellent immediate and short-term bonding effectiveness of etch-and-rinse adhesives, yet substantial reductions in resin- dentine bond strength occur after ageing. Degenerative phenomena involve hydrolysis of suboptimally polymerised hydrophilic resin components and degradation of mineral-deprived water-rich resin-sparse collagen matrices by matrix metalloproteinases and cysteine cathepsins. Silicate compounds, including calcium/sodium phosphosilicates, such as commercially available bioactive glass, and calcium-silicate Portland-derived cements are known to promote the formation of apatite in aqueous environments that contain calcium and phosphate (e.g. saliva); thus, we have raised questions about whether their presence at the bonded interface could increase the in vitro durability of resin-dentine bonds through crystal formation and self-sealing, in the presence of phosphate buffered saline or simulated body fluid solutions. In answering these questions, the objectives were accomplished by employing Bioglass® 45S5 in etch-and-rinse bonding procedures either (i) included within the composition of a resin adhesive as a tailored micro-filler, or (ii) applied directly onto acid-etched wetted dentine. Alternative light-curable methacrylate-based agents containing (iii) three modified calcium-silicates derived from ordinary Portland cement were also tested. Confirming the relative success of bioactive materials incorporated in the dentine bonding procedures required assessment of the potential to reduce nano-leakage, as well as their effect upon the strength of the bond over time. In order to explore these possibilities, which have not been previously investigated, a combination of methods were applied in the second experimental section. Bond strength variations were quantified using the microtensile test while scanning electron microscopy, confocal laser scanning microscopy and Knoop micro-indentation analysis were used to evaluate optically and mechanically adjustments to mineral and water content within the resin bonded-dentine interface. Initially, high microtensile values were achieved in each tested group. All the resin-dentine interfaces created with bonding agents containing micro-fillers showed an evident reduction of nano-leakage and mineral deposition after the ageing period. However, only adhesive systems containing Bioglass and two modified Portland cement-based micro- fillers were found to reduce nano-leakage with no negative effects on bond strength. Furthermore, specimens created with the same experimental adhesives did not restore micro-hardness to the level of sound dentine but were able to maintain statistically unaltered Knoop values. The second section is also composed of a set of preliminary studies that involved the use of up-to-date spectroscopic (attenuated total reflection Fourier transform infrared spectroscopy) and thermoanalytical (differential scanning calorimetry) techniques to predict the chemical-physical properties and apatite- forming ability of the novel ion-leachable hybrid materials. Lastly, the overall conclusions of the present work and directions for future research are discussed.
Date January 2013
CreatorsCorrado Profeta, Andrea
PublisherKing's College London (University of London)
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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