Dental alloys, and later zirconia, have been used in dentistry as frameworks for many years in making crowns and bridges veneered with ceramic e.g. feldspathic porcelain. Such methods of restoring teeth have been extensively studied both in the laboratory and clinically. Although such substructures have excellent strength there remains a large properties mismatch between these materials and bone or dentine e.g. elasticity. Furthermore, other drawbacks have been documented such as possible allergies, colouring of alloy margins, veneer chipping and excessive wear to opposing natural dentition. Polyaryletherketone (PAEK) thermoplastic biomaterial polymers such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) have been successfully applied in different medical applications with the latter recently being introduced to dentistry as a restorative material. The material is called Pekkton® ivory (Cendres+Métaux, SA, Switzerland) and is proposed to be used for fabricating both monolithic and bi-layered structures veneered with indirect composite resin. The manufacturer recommends methods similar to well-established restorations such as alloy and ceramic based crowns which makes it a user friendly material for both dental clinics and laboratories. Furthermore, the material’s properties such as high strength, low elastic modulus close to that of dentine, high temperature, chemical, hydrolysis and wear resistance, makes it a promising material for the replacement of tooth material. There is little published data about this material and hence the aim of this research was to evaluate the manufacturing process, aesthetic properties, structural integrity and durability of bi-layered crowns made from PEKK based thermoplastic high performance polymer (Pekkton® ivory, Cendres+Métaux, SA) and veneered with indirect light cured composite (Vita VM LC, VITA Zahnfabrik H. Rauter GmbH & Co.KG, DE). The processing route for Pekkton® ivory is either via milling or hot-pressing and the procedures were compared. The polymer-based restoration was compared to equivalent zirconia and metal based bi-layered restoration systems veneered with either light cured composite resin or feldspathic porcelain. Optical properties of each crown system were compared using a UV and visible light spectrophotometer. Structural integrity was compared for each system by testing the fracture resistance of the crowns using a universal testing machine and durability was evaluated by testing the fatigue limit and fatigue life using a fatigue chewing apparatus. The research hypothesis is that the PEKK polymer as anunderlying substructure material will perform equivalently to metal and zirconia substructures when veneered with light cured composite in the aspects of optical properties, strength and durability. The outcome of the study established a pressing protocol for PEKK using a standard ceramic pressing furnace where the pressed samples showed no significant differences in the CIEL*a*b* colour values, hardness or biaxial flexural strength to those samples produced via milling. There was no significant optical difference between the systems compared, the study found no evidence of difference in the CIEL*a*b* colour value of PEKK, zirconia or metal based samples when veneered with the same composite veneer. However, zirconia based groups displayed greater translucency with the composite veneer and feldspathic porcelain veneer. The fracture resistance of the PEKK and metal composite veneered crowns showed to be comparable, whereas zirconia based crowns demonstrated significantly lower fracture resistance. The durability of the PEKK composite veneered crowns showed the highest fatigue limit in comparison to the zirconia and metal composite veneered crowns. Similarly they showed the highest survival rate in the fatigue life assessment under the same cyclic load. Furthermore, the fracture mode was significantly different than observed with the zirconia and metal based crowns. The conclusion was that this material is promising for use as a restorative material and that clinical evaluation should be undertaken.

Head and neck cancers are a heterogeneous group of cancers with 90% of them originating from the squamous epithelium. Only 50% of patients survive on being diagnosed with this cancer after five years and this statistic has not improved over the last few decades. The main risk factors for head and neck squamous cell carcinoma (HNSCC) are smoking and alcohol consumption. In recent years, there has been more interest in understanding the function of elements involved in gene expression such as transcription factors and non-coding RNA's and their role in oncogenesis. HOX genes are transcription factors involved in oncogenesis and embryogenesis. In total, there are 39 HOX genes distributed in four clusters across the human genome. HOX genes have been observed to be aberrantly expressed in several cancers. MicroRNAs are non-coding short RNA transcripts which are approximately 21 nucleotides in length and lead to down-regulation of their target genes by acting on their 3'UTR. miR-196a is found in HOX gene cluster upstream of HOX9 paralogous group. Even miR-196a has been found to be aberrantly expressed in different cancers. The expression pattern of 39 HOX genes in cancer cell lines showed that HOXB9 was highly over-expressed compared to normal cells, which was further confirmed by qPCR in wider cell panel consisting of four normal, four oral pre-malignant and five HNSCC cell lines (p < 0.05). miR-196a was also found to be over-expressed in cancer cell lines compared to normal cells when similar sets of cell lines were used (p < 0.05). This data was also found to be replicated in tissue samples and it was observed that HOXB9 and miR-196a were significantly over-expressed in cancer tissue samples compared to normal tissue samples (p < 0.05). HOXB9 siRNA transfection into HNSCC cells showed significant decrease in invasion, migration and proliferation, whereas anti-miR-196a transfection in HNSCC cells showed significant decrease in invasion, migration and adhesion compared to negative control transfected HNSCC cells (p < 0.05). HOXB9 and miR-196a-1 are spatially closely related to each other on chromosome 17. To check if these two are co-transcribed on same primary transcript, nested PCR was performed with appropriate controls consisting of RNaseA treated RNA and no reverse transcriptase control, which suggested that novel primary transcript for HOXB9 and miR-196a-1 co-expression might exist in HNSCC cells which was confirmed by DNA sequencing. Expression microarray analysis was performed using anti-miR-196a in oral pre-malignant and HNSCC cells and pre-miR-196a in immortalized normal cells to assess if there were any novel direct targets of miR-196a in HNSCC. Based on qPCR (p < 0.05), dual luciferase reporter assay (p < 0.001) and site-directed mutagenesis, MAMDC2 was found to be a direct target of miR-196a in HNSCC. This is the first study in HNSCC looking at expression patterns of both miR-196a and HOXB9 and needs further work to validate them into biomarkers for early detection of HNSCC. miR-196a and HOXB9 could also be developed into potential therapeutic targets in HNSCC, particularly the novel primary transcript could be a novel therapeutic target. Further characterization of MAMDC2 is required but could turn into exciting therapeutic target as it is expressed as transmembrane receptor.

The Th17/IL-17 pathway is increasingly implicated in the pathogenesis of periodontitis. However the mechanisms that drive this pathway in humans and the relationship of this pathway to disease severity are not fully understood. The first aim of this thesis was to investigate whether the periodontal pathogens Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa) promote a Th17/IL-17 response in vitro, and to investigate the underlying mechanisms. The second aim was to determine the frequencies of IL-17+ CD4+ T cells in gingival tissue and peripheral blood from patients with periodontitis versus periodontally healthy control subjects. My results show that Pg and Aa activate monocytes, which can subsequently induce an IL-17/Th17 response in CD4+ T cells in vitro. The underlying mechanism involves the recognition of Pg by TLR2/4 on monocytes leading to an IL-1β/IL-23 dependent induction of IL-17 production by CD4+ T cells, which is further dependent in part on costimulation. The data also show that gingival tissue from patients with periodontitis contains increased frequencies of IL-17+ cells (predominantly CD4+ T cells) as well as IFNγ+ and TNFα+ cells relative to healthy subjects. IL-17+ CD4+ T cells and IL-17 protein are clearly detectable however in both diseased and healthy gingival tissue and GCF. No differences are observed in IL-17+ CD4+ T cell frequencies in peripheral blood from patients or healthy subjects. However, in vitro, Pg induces significantly higher IL- 17 production in anti-CD3 mAb-stimulated monocyte/CD4+ T cell co-cultures from patients with periodontitis compared to healthy controls.

Dental pulp inflamm'ation has major clinical significance. Recent research has suggested that the fibroblast has a role as driver of the inflammatory response. The term 'neurogenic inflammation' describes the contribution of the nervous system to local inflammatory responses and is thought to play an active and dynamic role in modulating pulpal inflammation. The function of the dental pulp fibroblast in the regulation of the neurogenic response to inflammation is unknown. This thesis presents a series of experimental studies investigating the role of the fibroblast in this aspect of inflammation. Cultured human dental' pulp fibroblasts populations were used in this study using a variety of in vitro techniques. The first part of the thesis involved the detection of substance P (SP) and neuropeptide Y (NPY) receptors, NK-I and NPY-YI respectively. Results demonstrated the expression of these receptors in pulp fibroblasts both at the mRNA and protein levels and their expression levels were regulated by cytokines and neuropeptides. The second part investigated the production of neuropeptides by pulp fibroblasts lnd results showed SP expression both at the mRNA and protein levels. Tissue levels of SP and NPY were quantified and compared in healthy and carious pulps, sho~ing increased expression during dental caries. The final section examined the responsiveness of pulp fibroblasts to SP and NPY. It was shown that pulp fibroblasts increased in proliferation in response to SP and had the ability to differentiate into odontoblasts. Furthermore, pulp fibroblasts expressed osteoprotegerin (OPO) and receptor activator of nuclear factor KB ligand (RANKL) indicating a role in 'clastic' activity. The present work demonstrated a potential role of the dental pulp fibroblast in the neurogenic inflammatory response with respect to SP and NPY, leading to a clearer understanding of their role in inflammation.

A study has been carried out on aspects of monofluorophosphate chemistry, with consideration for its use in toothpaste, A survey of techniques available for the analysis of mono- fluorophosphate was carried out. Conditions were established for the complete separation of monofluorophosphate and its major impurities by ion exchange chromatography. A detector based on heats of sorption and desorption was investigated as a means of automating the monitoring of species eluting from the chromatographic column. Procedures for determining monofluorophosphate and free fluoride ions using the fluoride ion electrode were devised. The methods were based on the determination of fluoride ion present in solution both with and without a preliminary acid hydrolysis step. Methods of preparing pure monofluorophosphate were investigated. Direct synthesis by heterogeneous gas-solid reactions on disodium hydrogen orthophosphate were attempted. Thionyl fluoride, sulphur tetrafluoride and hydrogen fluoride were the gaseous reagents investigated. A pure product vas not obtained in any of these reactions. Various chromatographic techniques, including preparative-layer and column chromatography were used in attempts to purify monofluorophosphate. A successful isolation of the pure ammonium salt was achieved using ion exchange chromatography followed by precipitation with ethanol and prolonged drying under high vacuum. Attempts to convert the pure compound to the sodium salt without decomposition were unsuccessful. The stability of the anion in glycerol-water mixtures was studied by investigating the kinetics of its hydrolysis in these media. The rates were studied at varying hydroxyl ion concentrations. The individual rate constants for the water and the hydroxyl ion reactions were determined for the various solvent compositions. Attempts were made to correlate the rate constants with certain solution parameters.

Oral lichen planus(OLP) is a chronic mucosal condition commonly encountered in Oral Medicine departments. It can cause patients significant discomfort, and only a small percentage, undergo complete remission. Recalcitrant lesions can be treated with various systemic medications including steroids. There is to date only weak evidence to suggest that these treatments are superior to placebo. This study was performed to determine whether homeopathic arsenicum album is useful in the treatment of OLP. A randomised double-blind clinical trial comparing homeopathic arsenicum album with placebo was carried out in the oral medicine department of the Edinburgh Dental Institute. The study covered a six-week period and ninety four patients participated. They were randomly assigned to a 6c homeopathic preparation of arsenicum album or to placebo, with all participants receiving placebo for the first week. After a pre-treatment visit, clinical review took place two and six weeks after commencing therapy. The same clinician scored the extent of the oral condition at all visits, and alleviation of symptoms was evaluated using a visual analogue scale diary and the Glasgow Homeopathic Hospital outcome scale. Ninety-two patients completed the study. No significant difference between the groups was seen on the visual analogue scores and there was no significance difference between the two groups with regard to response to treatment. However patients who were good prescribers for arsenicum album did show a difference between the groups with regard to response to treatment, which although not achieving statistical significance was strongly suggestive of an association. In conclusion homeopathic arsenicum album may be useful in the treatment of OLP, but more extensive studies need to be performed.

The linear distortion of the edentulous human mandible under functional loading was measured utilizing bilateral, anterior, osseointegrated oral implants as stable markers of bone position. These parasymphyseal implants were connected to a custom-made linear variable differential transducer (LVDT) to allow the recording of changes in mandibular arch width. Custom-made maxillary and mandibular prosthetic splints were manufactured to allow for the introduction of bite force transducers positioned bilaterally and posterior to the LVDT. These recorded biting forces in Newtons simultaneously with the LVDT recording in microns. This made possible further analysis of functional force in relation to the distortion of the human mandible. In total 16 human subjects were investigated from which 14 subjects provided useful data. The results were compared with previous studies which examined distortion of the human mandible during parafunctional activity and studies examining bite force levels in dentate as well as edentulous individuals. The results suggested that the level of distortion of the human mandible in function was similar with that seen in parafunctional activity and was at times was greater. The study also suggested that knowledge of the anatomical form of the atrophic lower jaw could be used to estimate the degree of distortion expected in a particular jaw during function. This, in turn, could inform on the optimal positioning of implants in the anterior of the mandible where the reduction of functional induced lateral stresses are considered important.

The aim of this research was to develop a composite dental material that has a higher monomer conversion by replacing the commonly used bulk monomer Bisphenol A-glycidyl methacrylate (BisGMA) with Urethane Dimethacrylate (UDMA) and by replacing Triethylene Glycol Dimethacrylate (TEGDMA) with a more biocompatible and larger diluent monomer Poly-Propylene Glycol Dimethacrylate (PPGDMA). The study assesses the effect of including an adhesion promoting monomer 4- Methacryloyloxyethyl trimellitate anhydride (4META), and different levels of initiator Camphorquinone (CQ) and polymerisable activator2-Dimethyl amino ethyl methacrylate (DMAEMA) on conversion, colour and clarity of composite monomers. The change in mass and volume and the final water sorption were evaluated for active composite materials that contained reminerelising monocalcium phosphate monohydrate (MCPM) and antibacterial, polylysine (PLS) and the colour change effect was assessed following immersion of the active composite discs in different solutions. Methods: Composite monomers were prepared by mixing UDMA and either PPGDMA or TEGDMA at a 3:1 ratio. CQ & DMAEMA were added at 0.5, 0.75 or 1 wt%. All monomers contained the adhesion promoting monomer 4META at 5 wt% intially). A standard 7-μm glass was used at powder/liquid ratio (PLR) of 4. UV-spectrometry was used to assess the colour and clarity of the monomers. FTIR (infrared) was employed to determine monomer conversion (MC) with 40s light exposure at 1 mm depth. With the elimination of the activator DMAEMA, clear UDMA/PPGDMA monomers that also contained 3 wt% 4META were used with hybrid glass, MCPM and PLS to contract composite discs that were used to check mass and volume changes at 37 Co. The effect of extrinsic discolouration of the experimented MCPM and PLS containing composites was also evaluated visually and using a colour measuring instrument (spectroshade). Values of colour change were recorded in the form of ΔE and the change was compared to a commercial material Z250. Results: Composites prepared with PPGDMA had approximately 20% higher conversion. DMAEMA resulted in increased clarity of the monomers by enhancing dissolution of 4META as demonstrated by UV spectrometry. The addition of DMAEMA had no significant effect on MC of monomers containing PPGDMA but increased MC in those containing TEGDMA. CQ concentration enhanced colour. Maximum conversion was obtained with 0.75 wt% CQ in UDMA/PPGDMA, 3 wt% 4META composites. Active composites with PLR 3 and 5 wt% of PLS resulted in the highest percentage in mass change with more than 4%. Higher volume changes were obtained with formulations of PLR 4 and 5 wt% PLS. There was no significant difference on effect of extrinsic discolouration of composite discs when visually assessed, however, using the Spectroshade it was clear that composites with PLR 5 were discoloured the most. Conclusions: Monomer conversion can be improved by changing the monomer content of dental composites. This will result in a reduction of leaching of unreacted monomers into the oral cavity and therefore improve biocompatibility. Composites containing PPGDMA had a better monomer conversion compared to those with TEGDMA. In this research, the main intrinsic factor that affected the colour of the monomer was the concentration of CQ whereas the effect of extrinsic discolouration can be attributed to PLR.

Peri-implantitis remains one of the main complications following implant placement. This condition leads to bone loss, impaired function, and if left untreated subsequent implant failure may result. Microcosm biofilms contaminating the implant surface are considered the main aetiological factor. Different anti-infective adjunctive treatments to non-surgical and surgical interventions as well as implant surface decontaminating techniques have been proposed for the therapy of peri-implantitis. However, no single decontamination intervention has been found to be superior. Notably, due to the infective nature of peri-implantitis, it becomes plausible to focus mainly on the elimination of targeted microbial pathogens and bacterial remnants. Current treatment modalities are limited by our ability to resolve unique peri-implant microbial niches in states of health and disease and to determine early disease progression induced by microbial shifts. Therefore, it is essential to explore the microbial ecology behind peri-implantitis and to develop novel implant surface decontamination methods, which will lead to resolution of this infective disease. This was the focus of the present thesis. Firstly, a systematic review on implant outcomes in treated periodontitis patients was presented. Herein, it is confirmed that the history of periodontitis, its type and severity play a detrimental role on the development of peri-implantitis. Secondly, an in vitro model of peri-implant microenvironments in an artificial mouth system was developed. This was done in the quest for understanding multispecies bacterial populations interactions, shifts and structure within peri-implant biofilms, as well as the impact of their niche. Then, previously disinfected titanium (Ti) discs substrata were analysed and a number of decontamination treatment protocols were tested in vitro and in vivo by the study of microbial remnants, biocompatibility dynamics, histomorphometrical analyses and surface chemistry. Finally, inspired by the bacterial diversity and abundances across the peri-implant microbial ecology in states of health and disease shown in the in vitro model, the subgingival microbiomes in patients with history of treated aggressive periodontitis were examined.

Resin based restorative composite materials are widely used for restoring both anterior and posterior teeth. Their major drawbacks, however, include complex bonding procedures, polymerisation shrinkage and potential for bond failure ultimately resulting in bacterial microleakage, recurrent caries and pulpal inflammation. This project’s aim was to characterise self-adhesive, antibacterial releasing, remineralising and high strength dental composites. The new composites contain UDMA as a bulk dimethacrylate monomer and PPGDMA as a high molecular weight diluent monomer instead of conventional Bis-GMA and TEGDMA respectively. NTGGMA adhesive co-initiator was added instead of DMPT. Adhesion promoting monomers 4-META or HEMA (5 wt %) were also included to enhance bonding to dentine (ivory). The monomers were combined with silane treated glass filler. This glass was mixed with total calcium phosphate levels (MCPM and TCP of equal mass) of 0, 10, 20 or 40 wt %. Furthermore, CHX and glass fibre were each included at 5 wt %. The powder liquid ratio was 3:1 by weight. Commercial dental composites Z250, Ecusphere and Gradia and experimental formulations with 4-META or HEMA and solely 100 wt % glass particles were used as controls. The degree of conversion after 20 s light cure was determined by FTIR. Cure data was used with the composite compositions to calculate the polymerisation shrinkage. The depth of cure was measured using ISO 4049. Subsequently, the mass and volume change and CHX release upon water immersion were determined over 5 and 4 months respectively. The mechanical properties biaxial flexural strength and modulus were determined dry and after 24 h, 7 days and 28 days immersion in water. The adhesion properties were assessed using a push out and shear test. Dry and hydrated ivory dentine with and without phosphoric acid etching for 20 s were investigated. The experiential formulations had ~ 77 % conversion as compared to ~ 50 – 60 % for commercial composites. The polymerisation shrinkage was ~ 3.4 – 3.7 % and the depth of cure decreased linearly with CaP increase after cured for 20 and 40 s. The mass and volume change and CHX release increased linearly with CaP increase and formulations with HEMA had higher water sorption and CHX releases compared to 4-META formulations. Control experimental composites achieved a flexural strength of ~170 MPa with no CHX or CaP. This decreased with CHX addition or increased CaP. Provided the CaP level was less than 20 %, however, strength was greater or comparable to Gradia and above 70 MPa even after immersion in water for 28 days. 5 The commercial composite exhibited the lowest push out and shear bond strengths to dentine. Replacement of HEMA with 4-META, increasing CaP, acid-etching or hydration of dentine and addition of Ibond adhesive, all significantly increased bond strengths between the composite and dentine. The new material, with adhesive monomer 4-META and reactive calcium phosphate, shows potential as a high conversion, antibacterial releasing, high strength and self-adhering composite, which should reduce restoration failure resulting from shrinkage and secondary caries. The use of ivory made it possible to determine the differences in bonding capability of multiple commercial and experimental formulations under wide ranging conditions.