The principal aim of this project is to examine posture and muscle activity when using an ergonomically designed saddle seat compared with a conventional seat during common dental procedures with the dental students and practising dentists. The study was conducted with practising dentists across the West Midlands and the dental students in the School of Dentistry – University of Birmingham. The study is mainly divided into a questionnaire survey of practising dentists, a questionnaire survey of dental student posture in the dental schools across the U.K, postural analysis, and a daily symptom survey of practising dentists and dental students, and finally the EMG analysis of practising dentists and dental students working posture. This thesis has established the relationship between posture, seating and muscle activity and indicates that use of an ergonomic aid (dental operator stool) may improve posture, decrease pain and muscle activity and may decrease the development of musculoskeletal disorders among dental students and dentists.

A novel imaging approach was developed for the purpose of counting cells from phase contrast microscopy images of laboratory grown (in vitro) cultures of epithelial cells. Validation through comparison with standard laboratory cell counting techniques showed this approach provided consistent and comparable results, whilst overcoming limitations of these existing techniques, such as operator variability and sample destruction. The imaging approach was subsequently applied to investigate the effects of silver nanoparticles (AgNP) on H400 oral keratinocytes. Concurrent investigations into antimicrobial effects of AgNP were performed on Escherichia coli, Staphylococcus aureus and Streptococcus mutans to provide models for Gram-positive and Gram-negative infection, and to compare with the literature and oral keratinocyte toxicity. It was found that AgNP elicit size-, dose- and time-dependent growth inhibition in both human cells and bacteria, although bacterial inhibition was not achieved without significant cytotoxicity at the same concentrations.

Implanted titanium (Ti) devices such as dental implants have been shown to produce metallic species within adjacent tissues. The effect of the presence of these species within oral epithelial tissues is currently not well characterised or known. This thesis investigates the effects of TiO\(_2\) nanoparticles (TiO\(_2\) NPs) at a range of concentrations on oral epithelial cells in the context of cell viability, cellular functions and interactions via a variety of methods. A co-culture model was established, and the difficulties of using a nano-scale insoluble stimulus were explored, and high content screening techniques were shown to be potentially more appropriate methods than conventional assays in this context. Interactions between TiO2 NPs and oral epithelial cells were imaged and investigated using a variety of imaging techniques. Oral epithelial cells were shown to take up TiO\(_2\) NPs within vacuole type structures. Cell viability appeared to not be affected at lower concentrations. Gene expression changes of oral epithelial cells in response to TiO\(_2\) NPs in the presence and absence of pathogenic bacteria were investigated. Cytokines important in cell-cell signalling were shown to bind TiO\(_2\) NPs, therefore creating potential for TiO\(_2\) NPs within tissues to modify immune responses within tissues adjacent to implanted Ti devices.

Portland cement (PC) is generally known for its various applications in the construction industry. However, since mineral trioxide aggregate (MTA), a PC based root filling material, obtained food and drug administration (FDA) approval in the late 1990’s there has been an increased interest in the use of the cement for other in vivo applications. PCs are durable, possess high compressive strengths, set in aqueous environments such as those found in vivo and have demonstrated desirable tissue responses as an endodontic sealant. The injectability of PC with various additives was investigated for use in clinical applications such as vertebroplasty (the stabilisation of a fractured vertebra with bone cement) using a syringe with a 2 mm aperture. Additives significantly improved cement injectability, decreased setting times from over 2 h to below 20 minutes while maintaining the compressive strength of the material. Cement characterisation methods including X-ray diffraction (XRD), helium pycnometry and zeta potential measurements were employed to elucidate the effect of the additives on the cement setting reaction. The biocompatibility of PC was investigated with fibroblast and bone marrow cells. The freshly mixed cement appeared cytotoxic while set cement upregulated genes associated with the osteogenic phenotype.

Oral keratinocyte behaviour were analysed in two and three dimensional cultures of an immortalised human H400 cellline and primary rat keratinocytes (PRKs) using a novel method of quantitative microscopy, RT-PCR data and immunohistochemistry profiles. Monolayer cultures were established in high and low calcium media at different cell densities and analysed prior to generating 3D organotypic cultures (OCs) onde-epidermalised dermis (DED), polyethylene terephthalate porous membrane (PET) and collagen gels for up to 14 days.H400 and PRKs proliferation in monolayer cultures was greater in low calcium medium compared with high calcium medium.Gene expression analysis indicated that adhesion and structural molecules including E-cadherin, plakophilin, desmocollin-3, desmogleins-3 and cytokeratins-1, -5, -6, -10, -13 were up-regulated by days 6 and 8 compared with day 4in high calcium medium. Immunohistochemical profiles and gene expression data of OCs on DED recapitulated those of normal oral epithelium. The final thickness of OCs as well as the degree of maturation/stratification was significantly greater on DED compared with other scaffolds used. Quantitative microscopy approaches enabled unbiased architectural characterisation of OCs and the ability to relate stratified organotypic epithelial structures to the normal oral mucosa. H400 and PRK OCs on DED at the air liquid interface demonstrated similar characteristics in terms of gene expression and protein distribution to the normal tissue architecture.

Dental enamel consists mainly of calcium-deficient hydroxyapatite (CDHA). The formation and evolution of enamel is a progressive and complex process the final stage of which is post-eruptive maturation (PEM), when mineralisation is completed following tooth eruption and exposure to oral fluids. Although PEM is directly correlated with decrease in caries susceptibility, a complete model to describe the whole process does not exist. Several reports have recently suggested that the previously observed caries decline, which started with the introduction of F- in drinking water and dental products, has stopped and is in some cases in reverse. New research approaches are therefore needed, which will focus on caries prevention and not treatment. This project monitored the in vitro effects of simulated PEM on the physicochemical properties of dental enamel and proposed a model which describes the whole process. For this purpose, primary and permanent bovine enamel was tested, using a suitably designed demineralisation/remineralisation laboratory protocol as well as characterisation techniques. The results were applied to the synthesis of enamel proxies, which could mimic the physicochemical properties of dental enamel; these proxies were evaluated for their potential to be used as enamel substitutes in dental research.

MicroCT was developed as a tool for assessing the quality of root canal preparation procedures in endodontics. Now debris can be measured in all areas of the canal with an automated calculation of the canal’s isthmus width. Investigations highlighted the biological variation present in the mandibular molar, with debris accumulating in isthmi, lateral canals and protrusions. Canals having an average isthmus width of 120-270μm resulted in 3.5x increase of debris compared to 271-630μm. Enlarging canals with a series of rotary files was shown to statistically significantly decrease debridement compared to a single reciprocating file. Regardless of irrigant or file motion, debris always remained in the canals which may become a source of reinfection, leading to treatment failure. Ultrasonic cleaning was investigated as a potential agent of a more thorough cleaning. A novel hydrogel with similar viscoelastic properties to some biofilms was created, and removal of this from canals was characterised by an initial rapid and unstable removal, followed by slower, constant viscous removal (isthmus) or the detaching of fragments of hydrogel (lateral canal). Ultrasonic cavitation effects were subsequently demonstrated to play a major role in removing biofilm in this model, although the creation of stable bubbles inhibited hydrogel removal.

The incidence of oral cancer continues to rise in the UK and in Scotland, with a steady increase in oral cavity cancer rates and a rapid increase in oropharyngeal cancer rates in the last decade. These rates are projected to increase further over the next decade, so there is a pressing need to optimise oral cancer prevention strategies. Tobacco and alcohol use are recognised as the major modifiable risk factors for developing oral cancer (both oral cavity and oropharyngeal). In addition, there is a significant increased risk for oral cancer among lower socioeconomic groups, males, and older age groups. Recently there has been recognition of the role of human papillomavirus in the aetiology of oropharyngeal cancers. The major behavioural risk factors (tobacco and alcohol) implicated in oral cancer risk are also associated with a wide range of diseases affecting oral and general health and are thus termed 'common risk factors', increasing the public health benefit should they be tackled. Given the pivotal role in oral cancer and wider disease prevention of reducing tobacco and alcohol use, there is a clear need to optimise the role of primary care dental professionals in delivering behavioural interventions. However, there are uncertainties about the best evidence for particular strategies and approaches to assess risk factors, advise and/or refer in the dental practice setting, with a particular lack of clarity in terms of the specific form and content of such interventions (for example: duration, tailoring to need, who delivers). In addition, the barriers and facilitators to implementation in primary care dental practice - from both the dental professional and patient perspectives - is relatively under-explored. This thesis describes studies undertaken to address these gaps in the knowledge and evidence-base. First a systematic overview was undertaken of systematic reviews and published (international) clinical guidelines. This aimed to identify the evidence on the best practice for the assessment of the major behavioural risk factors associated with oral cancer and for delivering effective behaviour change preventive interventions (in relation to, for example: advice, counselling, signposting/referral to preventive services) by dental professionals in primary care dental practice setting. This evidence was then explored via a study in primary care dental practices in Scotland utilising qualitative in-depth interviews with dental professionals, to identify barriers and facilitators to implementation, and to gather suggestions to inform the development of interventions to support dental professionals in delivering prevention. Finally, a small qualitative survey of patients attending primary care dental practice was conducted to explore barriers, facilitators, and acceptability of risk factor assessment and preventive interventions from the patients' perspective. The overview shows a lack of direct evidence from the dental practice setting (one high-quality systematic review relating to tobacco prevention and none relating to alcohol). However, relatively strong evidence and recommendations from other primary care (medical/pharmacy) settings were identified and synthesised, which could potentially be adapted and adopted by dental professionals. Overall the findings show that robust risk factor assessment is an important first step in any prevention intervention. There is a clear indication of the effectiveness of a "brief", in-person, motivational intervention for sustained tobacco abstinence and reduced alcohol consumption. The lack of detail particularly in relation to duration made it difficult to make a conclusion regarding precise specification of the duration of element of the "brief" interventions. For tobacco users, though longer (10-20 minutes) and intensive (more than 20 minutes, with follow-up visits) interventions have shown to be effective in increasing quit rates compared to no intervention, very brief (less than 5 minutes) interventions in a single session also showed comparable effectiveness to the longer brief or intensive interventions. While, for alcohol users, 10-15 minutes multi-contact interventions were most effective, compared to no intervention or very brief intervention or intensive intervention; brief interventions of 5 minutes duration were also reported to be equally effective. Thus, very brief or brief advice of up to 5 minutes, should be trialled for tobacco and alcohol respectively in a dental practice setting, tailored to patient motivational status. Exploring use of the dental team is supported, as effectiveness was generally independent of primary care provider (i.e. general practice physician or nurse). The qualitative studies on feasibility showed time and resources to be the major barriers from the dental professional perspective. Dental professionals also reported social barriers for a) using cancer as a term to frame preventive consultations and b) in delivering alcohol advice which may not be welcome by patients. Professionals were willing to receive training to overcome confidence issues in approaching behavioural aspects of both main risk factors. Patients however generally supported explicit conversations on oral cancer, and were amenable to alcohol as well as smoking advice, provided their stage-of-change (motivational readiness) was incorporated. The use of formal risk assessment tools to frame discussions was broadly supported by patients and professionals alike. Recommendations are made for testing a model of preventive consultation that draws from this best available evidence and addresses barriers for professionals and patients alike to help shape practice and support this important area of public health going forward.

This thesis, awarded by published work represents a collection of clinical studies that advance the knowledge of why to, and how best to, administer propofol safely using an innovative technique, 'Patient Maintained Sedation' (PMS).

Studying different types of dental pathology, wear, and developmental defects can allow inferences into diet and behaviour in a variety of ways. In this project data on these different variables were collected for South African hominins and compared with extant primates. The species studied include Paranthropus robustus, Australopithecus africanus, A. sediba, early Homo, Homo naledi, baboons, chimpanzees and gorillas. Macroscopic examination of each specimen was performed, with a 10X hand lens used to verify certain pathologies. Variables recorded include antemortem chipping, enamel hypoplasia, caries, occlusal wear, tertiary dentine, abscesses, and periodontal disease. Clear differences in frequencies were found in the different South African hominin species. Homo naledi displays high rates of chipping, especially small fractures above molar wear facets, likely reflecting a diet containing high levels of contaminants. Other noteworthy results include the high levels of pitting enamel hypoplasia in P. robustus molars compared to other species, likely due to a species-specific enamel formation property or developmental disturbance. The low rates of chipping in P. robustus does not fit with this species being a hard food specialist. Instead, the wear best supports a diet of low-quality tough vegetation. Australopithecus africanus likely had a broad diet, with angled molar wear, lack of caries, and high chipping frequencies supporting this conclusion. Seven new carious lesions are described, two from H. naledi and five P. robustus. Other, rarer, pathologies are also highlighted, including abscesses in an early Homo individual, root grooves caused by erosive wear in A. africanus and a case of amelogenesis imperfecta in a female chimpanzee. The main conclusion from this thesis as a whole is the substantial difference in frequencies of the different variables among hominin species, supporting the proposition that their diets differed substantially.