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The aim of this project was to develop three-dimensional (3-D) constructs of phosphate-based glass fibres (PGF) incorporated dense collagen matrices for biomedical and tissue engineering applications. For this, a novel method of "plastic compression" (PC) was used which rapidly removes fluid from hyper-hydrated collagen gels through the application of unconfined compressive load. The project objectives were: the understanding of structure-property relationship of PGF the understanding of the mechanisms of PC to produce dense collagenous matrices, and the application of PC to produce cellular 3-D constructs of PGF reinforced collagen matrices. PGF are unique glasses as they are degradable and biocompatible, and their degradation can be controlled through their chemistry. Two different quaternary glass systems incorporating CuO and Fe2O3 into the ternary glass system (in molar percentage) 50 P2O5- 30 CaO-20 Na2O were developed for either antibacterial or tissue engineering applications. These additional oxides were incorporated into the glass structure by partially substituting Na20. The rate of degradation was significantly decreased by the incorporation of both oxides possibly due to increased cross-link density, which correlated with an increase in the density and glass transition temperature. There was a further decrease in degradation with increasing fibre diameter. The amount of Cu2+ release increased with increasing CuO content, and 10 mol % was the most effective in killing Staphylococcus epidermidis. YqjOt, had a much more significant effect on rate of degradation, and the rate of Fe3+ release decreased with increasing Fe203 content. From the compositions and fibre diameters investigated, fibres containing 3-5 mol % Fe203 with a diameter of 30 urn were more durable, and therefore suitable for use as scaffolds. Furthermore, upon long term degradation, the iron containing glass systems showed the potential for tube formation. PC depends mainly on the ability of collagen to undergo creep deformation and no recovery upon load removal. Using this principle, a dense collagen matrix with improved mechanical properties was produced. PC was also successful in producing PGF-PC collagen constructs with different compositions. It was anticipated that PGF would initially further enhance the mechanical properties of the constructs. Moreover, PGF also provided the intriguing possibility of capillary-like channels within the collagen for cell and nutrient transportations. The effect of PGF incorporation was assessed morphologically, mechanically, and biologically using live/dead staining. Increasing the proportion of PGF yielded significantly stiffer, stronger constructs while compromising their compliance. At greatest, only 20 % cell death due to either PC or PGF incorporation occurred, however, a significant increase in cell viability after 24 hours was observed. The findings suggested that PC is effective for engineering composite, biomimetic collagen matrices with controllable properties.

This thesis studies in depth the various processes, materials and advances in dental and cranial facial techniques and methods. Two main important areas in the field of cranial facial engineering have been addressed. The first of it being techniques and methods for better dental restoration and the second being evaluation of wear and tear on dental tools and materials for enhanced life and performance. The work in all the chapters focuses on methods and materials that are being used at the present time. These techniques are being used in the prostheses on a day to day basis to fabricate custom titanium bone replacement prostheses. Due to the growing need and importance of biomaterials in the dental and medical fields this research in this work has been directed primarily at solving practical clinical problems associated with new techniques and materials. I confirm that the thesis is my own work; and that all published or other sources of material consulted have been acknowledged in notes to the text or the bibliography.

This thesis presents a new 6 DOF in vitro dental chewing simulator based on a 6-6 spatial parallel kinematics and a parallel robotic implicit position/force hybrid controller to replicate chewing movements and wear formations on dental components, such as crowns, bridges or a full set of teeth. The human mandible, guided by passive structures such as posterior teeth and the two temporomandibular joints moves with up to 6 DOF in Cartesian space. Currently available biaxial operated wear simulators lack the ability to perform these chewing movements. Their lack of sufficient DOF enables them only to replicate the sliding motion of a single occlusal contact point by neglecting rotational movements and the motion along one Cartesian axis. The motion and forces of more than one occlusal contact point cannot accurately be replicated by these instruments. Furthermore, the majority of wear simulators are not suitable to simultaneously control the main wear affecting parameters such as sliding motion and bite forces in the constraint contact phase of the human chewing cycle. It has been shown that such discrepancies between true in vivo and simulated in vitro situation influences the outcome and the quality of wear studies using such approaches. The new developed dental wear simulator can be used for single and multi-occlusal contact testing due to its ability to move with up to 6 DOF. Recorded human mandibular motion and occlusal force data correspond well to previous research. These force and motion data are the reference input of the simulator. Three experimental studies outlined the importance of simultaneous force and position control for in vitro wear studies. These studies show that combined force/position control improves the quality of wear studies and that 6 DOF in vitro simulators are necessary to compare in vitro research to clinical in vivo wear studies. In addition, the experiments demonstrated that the simulator can reliabily perform long-term, realistic material science studies to a high standard of accuracy in motion and force.

This study measured the distribution of the interval between placement and next intervention on the same tooth for direct restorations of teeth in the General Dental Services of the NHS in England and Wales between January 1991 and December 2002. Three different sets of treatment data covering the period were used, involving over 1.3 million restorations. Standard and modified Kaplan-Meier, and three different cross-sectional techniques were used to estimate empirical survival curves, and Cox-regression was used to model the relationship with risk factors associated with the dentist, the patient, geographical location, time, tooth position and type of restoration and cavity. Overall, median survival was slightly more than eight years from placement to re-intervention. The rates of survival without intervention after one year, five years and ten years were, respectively, 89%, 62% and 46%. Key risk factors associated with survival were type of cavity, tooth position, patient age, patient treatment history and patient attendance history. The underlying baseline function of the Cox-regression analysis was closely modelled by both a Weibull and a cubic function. The robustness of the findings was demonstrated by a full replication of the eleven-year analysis using a completely separate fourth sample from the DPB’s data archive.