Melbourne Dental School - Theses
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ItemScreening for Type 2 Diabetes Mellitus initiated through the dental setting: a cost-effectiveness analysis( 2019)Background. Diabetes Mellitus (DM) is the fastest growing chronic condition in Australia. Approximately, 30% of DM in Australia is undiagnosed. Early identification may delay or prevent the onset of DM with minimal complication. In the Western Pacific (WP) region, Australia has the highest per capita spending on DM. With the rising cost of healthcare, increasing emphasis is being made to ensure that health interventions are not only practical but also cost-effective that can save resources which otherwise may have to be spent on complication and hospital admission. By stretching the number of contact points between health care providers and individuals seeking care, there is plenty of opportunity for early identification of asymptomatic individuals with Type 2 Diabetes Mellitus (T2DM). With this link between DM and periodontal disease, dentists may have an unrealized opportunity to identify risk groups and refer them to physicians for further care. For any screening activity in the dental setting, the participation of Oral Health Professionals (OHP) is important. Little is known as to how well oral health professionals incorporate into practice on the evidence supporting the link between DM and periodontal disease. Besides that, no previous studies have reported the cost-effectiveness of opportunistic screening using a diabetes risk assessment tool in the dental setting. As such, the aim of the thesis is twofold. To explore the Victorian oral health professionals (OHP) knowledge, attitude and practice (KAP) around DM and to evaluate the overall economic justification of screening for diabetes and pre-diabetes in the dental setting. Methods. A cross-sectional survey of Victorian OHP was conducted. The questionnaire consisted of sociodemographic, practice characteristics and diabetes-related KAP. Descriptive statistics with frequencies and percentages were used to summarize the variables. A Mann-Whitney and Kruskal-Wallis test was performed to determine differences in OHP response to the KAP questions. The screening model consists of a decision tree and a disease progression Markov model to identify the risk of T2DM over a ten-year period. Literature data were used for the risk categorisation and disease transition for health states. The cost-effectiveness of screening was compared to no screening option. A hypothetical population of 40 to 74-year-old Victorian dental patients with no previous history of DM were screened with the Australian type 2 Diabetes Risk Assessment Tool (AUSDRISK). Those identified as high-risk follow-up with the physician for screen diagnosis using Fasting Plasma Glucose (FPG). Based on the previous finding from two-step screening in the dental setting the model made an assumption that 21.5% of the dental patient identified as high risk follow up with the physician. The cost-effectiveness was analysed from a societal perspective. The main outcome measure includes cost per case detected as undiagnosed T2DM, new cases of T2DM. A univariate sensitivity analysis was performed to determine the effect of different physician follow-up rate from the dental setting to identify undiagnosed T2DM. Results. The survey analysis included 197 OHP. General and specialist dentist constitute 65% and 11% of the response and the remainder were dental hygienist and therapist. Around 86% of the OHP showed adequate knowledge of DM. Further 93% and 81% of the OHP expressed positive attitude and practice behaviour towards T2DM screening and management. For OHP to perform chair-side screening for DM, 58% felt it was essential, and 70% felt it was appropriate. More female (67%) and public sector OHP (79%) felt it is important to conduct chair-side screening for T2DM. The majority (65.4%) of the OHP agreed on consent as the most important and insurance coverage as the least important (43%) consideration for T2DM screening. Under model assumption, the number of dental patients identified as undiagnosed T2DM and pre-diabetes were 4,108 (0.3%) and 10,072 (0.8%). The cost incurred for one new case of undiagnosed T2DM and pre-diabetes were AUD 15,508 and AUD 6,325. The Number Needed to Screen (NNS) to identify one new case of undiagnosed T2DM and pre-diabetes were 288 and 117. Among those followed up with the physician, at the end of five years, 81.5% had Normal Glucose Tolerance (NGT), 8.1% had Impaired Fasting Glucose (IFG), 6.9% had T2DM, and the all-cause mortality was 3.5%. At the end of the ten-year period, 10% had T2DM. The overall and disease-free survival was 92.8% and 82.8%. Discussion. Majority of OHPs had adequate knowledge and a positive attitude towards T2DM screening in the dental setting. The survey identified patient willingness as the most important consideration among the OHPs for implementing T2DM screening in the dental setting. The screening model identified several methodological challenges due to incongruent data and unsuitable comparator. Despite that, opportunistic screening with AUSDRISK was found to be neither clinically effective nor cost-effective compared to screening in the medical setting. High screening cost, poor predictive ability of AUSDRISK, low prevalence of the disease, unnecessary physician referral besides uncertain benefits, fear of over diagnosis and poor patient compliance makes screening for T2DM in the dental setting difficult to justify. The model findings are in line with previous estimates on AUSDSRISK as a screening tool. In financially constrained health system resource allocation will need to be based on favourable evidence that screening can reduce disease levels in the community, demonstrate health benefits at an acceptable cost. A two-step opportunistic screening that includes a risk assessment followed by a Point-of-Care (PoC) HbA1c may offer some benefits in the low- and middle-income countries.
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ItemDental implant maintenance and home hygiene – information pathways, clinical practice and patient realities in Australia( 2019)Dental implants have widened treatment paradigms in dentistry since the 1980s and are placed in the millions annually around the world, but plaque-induced peri-implant diseases which can reduce treatment success are not completely understood. The real-life practices of patients and dental practitioners in minimising peri-implant disease risks have not been widely documented. The information sources from which dental practitioners learn peri-implant maintenance are highly variable and also rarely documented. This thesis investigated the flow of information in implant maintenance and hygiene in Australia: from research, to educators, dental practitioners and patients; the limitations present and areas of further development. A series of cross-sectional surveys was conducted to investigate: the hygiene habits of patients with implants in the community, patient-reported outcomes, implant success and peri-implant outcomes; the implant dentistry training attended and provision of implant services by dental practitioners in Australia; dental practitioners’ preferences in implant hygiene instruction, diagnostics and maintenance, including the role of oral health practitioners; and the teaching of implant maintenance topics within implant dentistry education in Australia. A survey of 51 patients in private general dental practice found 7.8% had peri-implantitis and 33.3% had peri-implant mucositis (7.7% and 24.4% of 78 implants respectively). At the implant level, peri-implant disease prevalence was significantly higher where implants were cleaned only with toothbrushing (p<0.001) or had plaque/calculus present (p<0.001). Implant success was significantly reduced if any local factors affecting hygiene accessibility were present (p<0.001). Patients recalled mixed provision of implant hygiene instructions from their treating dentists and reported 7.7% of implants as aesthetically unsatisfactory and 9.0% as having symptoms. A survey of 303 general dentists found continuing professional development was the most common highest level of implant training attended, graduation decade affected the types of implant training attended, and dentists are providing implant treatments increasingly earlier in their careers. Highest attended training level was significantly correlated to greater complexity of implant treatment and maintenance services provided, and a more preventative approach in implant hygiene instruction. Conversely, dentists with little implant training and/or who do not provide implant treatments may not be providing optimum maintenance and preventative information. Compared with the dentists, 154 oral health practitioners surveyed reported more preventative and evidence-based attitudes to implant hygiene instruction, diagnostics and maintenance, and they provided the bulk of preventative services in their workplaces. Implant dentistry education convenors were surveyed (24 respondents outlining 43 programs) and implant maintenance teaching was found to generally reflect the available literature, which is established for diagnostics but limited for patient-performed hygiene, professional maintenance and review. Some respondents acknowledged the need to update their inclusion of implant maintenance topics. As the peri-implant disease, hygiene and maintenance literature develops, current challenges include multi-disciplinary communication and the continuing development of implant dentistry education. By documenting current trends and identifying areas for clinical improvement and further research, it is hoped that this thesis, through the lens of implant hygiene and maintenance, provides possible future pathways for implant dentistry in Australia, to ultimately optimise treatment success and positive patient outcomes.
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ItemThe Role of Candida in Oral Lichen Planus (OLP)( 2019)Purpose: Oral lichen planus (OLP) is a chronic condition characterised by T cell mediated destructions that is currently of unknown cause. OLP can be variably symptomatic with some patients experiencing no symptoms and others requiring extensive symptomatic management. Candida spp. can be found in association with OLP and due to this prophylactic treatment for Candida spp. is usually accounted for in the symptomatic management of OLP. This is despite current evidence not supporting concurrent use of antifungal therapy in the management of OLP with topical steroids. A potential hypothesis for the cause of OLP is an interaction of host genetic susceptibility combined with an environmental trigger that initiates disease in the susceptible host. Another equally likely hypothesis is that OLP is a true autoimmune condition with autoimmunity directed against a currently unknown epithelial autoantigen. The oral cavity represents a unique microenvironment that plays host to many commensal and opportunistic microorganisms. The oral microbiota, specifically Candida spp., could act as an aetiological trigger for the chronic T-cell mediated inflammation the defines OLP, specifically through activation of mucosal associated invariant (MAIT) cells. The role of Candida in the aetiopathogenesis and symptomatic management of OLP is currently unknown. Hypothesis and Aim: The overall hypothesis was that Candida may play an aetiological role in the OLP disease process exerting an effect on T cells and cytokine expression and that adjunctive treatment is required in the symptomatic management of OLP. The overall aim of this study was to determine whether Candida plays an aetiological role in OLP as well as determine if specific treatment of Candida is required in symptomatic patients with OLP. Materials and Methods: 14 control and 7 OLP test patients, 3 assigned to the placebo and 4 assigned to the antifungal treatment group, completed the clinical study. Assessments of clinical appearance, symptoms, Candida, salivary acetaldehyde and medication use were made at 0, 6 and 12 weeks for OLP patients with assessments of Candida and salivary acetaldehyde made at baseline only for controls. 20 random OLP formalin fixed paraffin embedded (FFPE) samples were stained using a fluorescent multiplex immunohistochemistry (mIHC) protocol for the markers cluster of differentiation (CD)3, CD8, DAPI, interleukin 18 receptor 1 (IL18R1), CD161, MR-1 and T cell receptor (TCR) V alpha 7.2. The slides were scanned with the Vectra Automated Multispectral Imaging System (PerkinElmer, USA) to generate multispectral images (MSI). The MSI were then analysed with tissue segmentation and single antibody algorithms for both HALO (Indica Labs, USA) and inForm 2.4.1 (PerkinElmer, USA) to validate a method for quantitative analysis. Following validation of HALO (Indica Labs, USA) for quantitative analysis the above process was repeated on 89 FFPE biopsy tissue samples from 73 patients with OLP (28 asymptomatic, 30 symptomatic and 16 samples with concurrent Candida (9 symptomatic and 7 asymptomatic), for comparison with 15 patient samples of fibroepithelial polyp (FEP). All samples were tested for presence of Candida with periodic acid-Schiff (PAS) staining. A BioPlex assay was performed to measure the cytokines interferon gamma, tumour necrosis factor alpha, interleukin (IL) 17A, IL-18, IL-12p40, IL-12p70, IL-22 and IL-23. Supernatant for this experiment was collected at 8, 12 and 24 hours following prior incubation of peripheral blood mononuclear cells (PBMC) in PBMC media supplemented with either 10% v/v effluent derived from C. albicans biofilms or 10% v/v artificial salivary media (ASM). In addition, some wells were supplemented with either CD28 and/or phorbol 12-myristate 13-acetate (PMA)/Ionomycin. Flow cytometry was performed using TCRV alpha 7.2, CD3, CD161, CD218a, CD4, CD8 and CD45 to define MAIT cells and T cell subsets. Prior to performing flow cytometry PBMC were incubated for 6 hours in PBMC media supplemented with either effluent derived from C. albicans biofilms or 10% v/v ASM with or without CD28. Results: Results of this study showed no significant differences existed between the control group and the OLP test group at baseline with respect levels of salivary acetaldehyde, and Candida colony forming units (CFU). Downward trends were noted in both groups with respect to clinical appearance and subjective analysis of symptoms from baseline to 12 weeks. Trends noted from assessment of CFU and salivary acetylaldehyde levels between the test groups should be viewed with caution due low levels of detection at baseline and the wide spread of data. Minor variability between the tissue segmentation algorithms with the trained algorithm for inForm 2.4.1 (PerkinElmer, USA) being the slightly less variable of the two. For quantitative cell analysis and identification of single antibody positive cells HALO (Indica Labs, USA) proved to be the least variable of the two trained algorithms. The presence of MAIT cell phenotypes were confirmed within the subepithelial infiltrate of OLP. Reduced MAIT cell phenotype expression was noted in the presence of Candida and/or symptoms in OLP with decreased expression of CD161 noted in the presence of symptoms whilst decreased expression of TCRV alpha 7.2 was noted in the presence of Candida. Presence of PMA/Ionomycin and Candida effluent were factors that increased the expression of interferon gamma, tumour necrosis factor alpha, IL-17A, IL-18, IL-22 and IL-23, cytokines that are associated with MAIT cell activation. Across all timepoints the presence of Candida effluent and CD28 resulted in upregulation of IL-18 and tumour necrosis factor alpha. MAIT cells were not significantly affected by the presence of either effluent or CD28 suggesting that neither Candida effluent nor CD28 alone or the combination of the two were shown to induce MAIT cell proliferation. Conclusion: Adjunctive treatment of symptomatic OLP with a topical antifungal did not significantly affect the presence of symptoms, erythema, CFU, Candida spp. or production of salivary acetaldehyde. HALO (Indica Labs, USA) was shown to be the more reliable program for mIHC quantitative cell analysis in FFPE OLP tissue. Analysis of mIHC in OLP FFPE tissue identified MAIT cells within the OLP inflammatory infiltrate with decreased expression of CD161 and TCRV alpha 7.2 noted in the presence of symptoms and Candida respectively. Finally, Candida effluent was unable to induce proliferation of MAIT cells in PBMC. However, cytokines associated MAIT cell activation and OLP, specifically interferon gamma, tumour necrosis factor alpha, IL-17A, IL-18, IL-22 and IL-23, were shown to be upregulated in the presence of Candida effluent derived from C. albicans biofilm.
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ItemNon-smokers, Non-drinkers: Assessing surgical outcomes in a clinically distinct cohort of Oral Squamous Cell Carcinoma patients( 2019)Background Tobacco and alcohol intake are responsible for approximately 65-70% and 20-35% respectively of oral squamous cell carcinomas (SCC). Non-smoking, non-drinking (NSND) patients represent approximately 13-35% of the oral SCC population and are more likely to be young (Mean 20-35 years) or elderly (Over 70 years) females with a predilection for tongue, gingivae and lower lip sites. Although approximately 24% of head and neck cancers occur in patients over 70 years old, there are few published reports of oral SCC in elderly patients. This group appears to be characterized by a higher proportion of NSND females. Bone invasion by oral SCC necessitates jaw resection. Ideally, pre-operative imaging can be used to guide resection. The current rate of non-invaded mandible resections ranges between 20 and 100%. Even with free-flap reconstruction, segmental resection still results in cosmetic and functional deficits, donor site morbidity and significant physiological strain resulting in increased risk, prolonged recovery and need for rehabilitation. Decreased physiological reserve and multiple medical co-morbidities make complex surgery undesirable in an elderly population. Marginal resection aims to maintain bony continuity to avoid complex reconstruction. Objectives The objectives of this study were: 1. Examine differences in survival and clinical outcomes of elderly patients without traditional risk factors presenting with oral squamous cell carcinoma. 2. Determine the accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) at identifying bone invasion in oral SCC. Materials & Methods Retrospective review of 287 consecutive patients divided into 2 treatment period cohorts treated for oral SCC between the 1st Jan 2007 and 31st Dec 2012.. Patients were classified as either smoker-drinkers (SD) or non-smoking, non-drinking (NSND). Only patients with oral sub-site primaries according to ICD-10 were included. Carcinomas of the lip, tonsil, base of tongue and oro-pharyngeal sub-sites were excluded. A subset of 109 patients who underwent mandibular resection were also reviewed for bone invasion. 83 of these patients had pre-operative CT imaging studies of diagnostic quality available for review and 72 underwent MRI which were compared to histological resection specimens. Results Of the study population (N=287), 24.4% were NSND and 9.75% were NSND elderly (older than 70 years) females. Disease specific survival at 5 years was significantly reduced when NSND elderly females were compared to all other patients (p <0.001) as well as age matched controls (p = 0.006). This effect was verified independently in each cohort. Bone invasion was detected in 44 out of 109 (40.4%) resection specimens. Bone invasion was identified on CT imaging in 31 out of 83 cases (37.3%) and by MRI in 35 out of 72 cases (48.6%). The sensitivity and specificity of CT for detecting bone invasion was 69.0% and 79.6% respectively. The sensitivity and specificity of MRI for detecting bone invasion was 87.1% and 80.5% respectively. Conclusions The results of this study suggest that NSND elderly females are a distinct patient population with poorer disease specific survival outcomes and that negative imaging studies should not preclude an oncologically safe bony resection if indicated on clinical grounds.
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ItemThe effectiveness of using a periodontal endoscope as an adjunct to non-surgical periodontal therapy: clinical, radiographic and microbiological results( 2019)ABSTRACT Non-surgical periodontal therapy has been one of the main treatment approaches for managing patients with periodontal disease for decades. The aim of this treatment is to remove bacteria and subgingival deposits, create a “clinically healthy” environment and improve microbial levels to levels that is compatible with health. Conventional non-surgical debridement includes both hand and powered instruments with the ideal end point being a smooth root surface. Periodontal endoscopy was developed in the late 1990s and features miniaturized digital video technology allowing the operator to directly visualise the subgingival environment and at the same time remove any calculus or debris from the root surface with the use of hand or powered instruments. The benefits of direct visualisation technology in improving clinical and inflammatory outcomes were demonstrated in retrospective and prospective studies as well as randomised controlled studies utilizing either split-mouth design or parallel design. However, there was a need to investigate if endoscope scaling and root debridement (SRD) is more effective in reducing levels and numbers of periodontal pathogens as compared to conventional nonsurgical treatment. Also, if bacterial counts decrease, can they be maintained or reduced even further with strict three monthly supportive periodontal maintenance therapy (SPT). Osseous changes can occur after nonsurgical periodontal therapy. However, it is often difficult to determine if changes have occurred due to limitations with conventional radiography. This study included the use of standardized radiographs using customized positioning stents and paralleling x-ray holding devices. Digital radiography and digital software were used to determine areas of osseous change. Aims 1. To compare endoscope-assisted SRD (SRD-with endoscope) to traditional SRD (SRD-only) in reducing clinical parameters over a 12-month period. 2. To assess if endoscope assisted SRD shows more evidence of radiographic changes after the 12-month period compared to conventional SRD. 3. To compare bacterial counts of 11 species including Aggregatibacter(Actinobacillus)actinomycetemcomitans)(A. actinomycetemcomitans); the red complex ((Porphyromonas gingivalis(P. gingivalis); Tannerella forsythia (T. forsythia) and Treponema denticola (T. denticola)); the orange complex ((Prevotella intermedia (P. intermedia); Peptostreptococcus micros (P. micros) ; Fusobacterium nucleatum/periodonticum (F. nucleatum)); the orange-associated complex ((Campylobacter rectus (C. rectus); Eubacterium nodatum (E. nodatum)); the green complex ((Eikenella corrodens (E. corrodens)) and Capnocytophaga species ((Capnocytophaga sp.) (C. sputigena; C. gingivalis; C. ochracea)) in both groups over a 12-month period. 4. To determine the need for surgical intervention in both test and control groups after the 12-month treatment. Materials and Methods The study included 38 participants diagnosed with chronic moderate to advanced periodontitis. Nineteen participants were included in the test group (SRD-with perioscope) and 19 in the control group (SRD-only) by consecutive allocation. Clinical examination included probing pocket depths (PPD), probing attachment levels (PAL), gingival recession, assessment of furcation, mobility, bleeding on probing (BOP) and plaque scores (PI). The measurements were recorded at baseline, three and twelve months and differences in means between groups were calculated for all clinical parameters. The Hain Lifescience Micro-IDent test was utilized for the microbial analyses. Five sterile paper points were inserted into five of the deepest pockets, placed into a sterile test tube and sent in a water-resistant bag to Nehren, Germany for analysis. Eleven putative pathogens namely A. actinomycetemcomitans, P. gingivalis, P. intermedia , T. forsythia, T. denticola, P. micro, F. nucleatum, C. rectus, E. nodatum, E. corrodens and Capnocytophaga sp., were analysed at each time point and compared between the control (SRD-only) and test group (SRD-with perioscope). Analysis of pathogens in their respective complexes namely the red, orange, orange-associated and green complexes were also included. Standardised radiographs were taken at sites with the deepest pockets and in sites displaying angular/vertical bone loss using positioning stents at the baseline and 12-months. The Digimizer Image Analysis software (2005-2018 MedCalc Software bvba, Belgium) was used to measure from the cemento-enamel junction (CEJ) to the alveolar bone crest and changes were tracked in millimetres between radiographs taken pre-SRD and at twelve months. Linear measurements were utilized to determine mean radiographic bone levels (RBL). Results There were no significant differences between groups with regards to age, gender, medical history and disease severity. Both groups showed significant improvements in all clinical parameters after therapy (p<0.05). At three months, no statistically significant differences could be found between groups with mean PPD, mean PAL, BOP and PI. However, for PPDs 7-9 mm the test group had a significantly lower percentage as compared to the control group. At twelve months, the mean PPD was found to be significantly lower in the test group (2.70+0.2 mm) as compared to the control group (2.96+0.4 mm) (p<0.05). In addition, the test group also had lower BOP (4.3+3.2%) percentage as compared to the control group (11.95+7.1%). PI percentage (25.61+3.9%) was also reported to be lower in this group as compared to the control group (30.11+6.3%). The test group had less change in gingival recession (-0.13+0.2 mm) as compared to the control group (-0.5+0.6 mm) from baseline to twelve months (p<0.05). There were no statistically significant differences found between the test and control groups with regards to reduction of periodontal pathogens and their complexes (p>0.05). Both SRD-only and SRD-with perioscope resulted in decreases in numbers of periodontal pathogens including, P. gingivalis, T. forsythia, T. denticola, P. intermedia, P. micro, E. nodatum and E. corrodens post-therapy and at twelve months with numbers remaining below pre-treatment levels. However, A. actinomycetemcomitans, C. rectus, and Capnocytophaga sp. decreased post-therapy in both groups but increased at twelve months. F. nucleatum increased in both groups post-SRD and then were reported at lower levels at twelve months. Both the red and orange complex had lower numbers in the test group at twelve months, with the control group having lower numbers of the green and orange-associated complexes. The mean change in RBL was significantly higher in the test group (0.69+0.3 mm) as compared to the control group (0.49+0.2 mm) (p<0.05). This positive change in mean RBL is indicative of more radiographic bone gain in the test group. There were no differences reported between groups with regards to mean change in RBL for single-rooted teeth (p>0.05). However, for multi-rooted teeth more radiographic bone gain was observed in the test group (0.83+0.5 mm) with a higher mean change in RBL as compared to the control group (0.46+0.4 mm) (p<0.05). The test group had a higher frequency of RBL between 0.5 mm and 1.0 mm and 1.0 mm to 1.5 mm as compared to the control group, inferring that the test group had more sites with radiographic bone gain in this range as compared to the control group. Conclusions Both non-surgical treatment methods used resulted in positive outcomes in clinical, microbiological and radiographic parameters. The adjunctive use of the perioscope significantly improved PPDs 7-9 mm at three and twelve months. The mean PPD at twelve months was significantly lower in the test group as compared to the control group. Less change in gingival recession was observed using the endoscope. The test group had significantly lower BOP% and PI% at twelve months. No significant differences between groups were observed with analyses of the eleven pathogens and complexes of bacteria. The significantly higher mean RBL observed in the test group as compared to the control group is suggestive of more radiographic bone gain in this group. This outcome was also observed for multi-rooted teeth in the test group.
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ItemExploring psychological correlates of toothbrushing behaviour - a systematic review of current research and a qualitative exploration of real-time influences( 2019)This thesis explores the psychological mechanisms of toothbrushing routines among younger adults. With individual attitudes and beliefs linked to toothbrushing engagement, an improved understanding of these mechanisms is expected to have benefits for preventive oral health efforts. Current limitations are that: a) there is little agreement regarding the psychological constructs that best correlate with toothbrushing, and b) there is little explanation around the dynamic, real-time influences that may influence toothbrushing on a daily basis. Two projects were designed: a systematic review of the current literature to determine the psychological constructs that best correlate with toothbrushing, and a qualitative exploration of how real-time variables may impact toothbrushing. The systematic review screened 1117 articles. Analysis of the final sample (N=13) found that variables related to attitudes (r=0.30), self-efficacy (r=0.48), and intentions (r=0.59) had significant correlations with toothbrushing behaviour. However, findings were distorted by observations that methodology was poor/average, with the use of validated measures and reporting of statistics lacking across all studies. The qualitative study consisted of in-depth interviews (N=23) that discussed toothbrushing routines, perceived attitudes and norms related to toothbrushing, and if toothbrushing routines ever changed from day-to-day. Individuals reported that routines were subject to change, with morning toothbrushing often skipped due to stress, and night-time due to exhaustion. Those who rarely neglected brushing reported being motivated by personal reasons rather than social pressures. Findings suggest the locus of motivations and ability to self-regulate during stress and/or feelings of tiredness may play a role in the experience of real-time barriers to toothbrushing. This thesis highlights the importance of exploring psychological mechanisms within the oral health field. Future research might attempt to quantify how self-regulation relates to toothbrushing engagement in terms of real-time decision making. Researchers are suggested to investigate the role of social pressures relative to more intrinsic motivations, and are advised to focus on study design, validated measures and the use of past literature. Clinicians are advised to be conscious of the role that situational barriers may have on toothbrushing behaviour, and should consider fostering intrinsic motivation within patients, rather than using fear or social norms to elicit improved toothbrushing. Limitations to the thesis and additional suggestions for research and further exploration within this field are discussed.
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ItemA study of various factors that influence the success of posterior resin-based restorations( 2019)This thesis is centred on the investigation of several physical properties related to bulk-fill resin composites that may influence the success of posterior resin-based restorations. In addition, a test methodology to investigate the fracture toughness of brittle restorative materials was evaluated, including the potential influence of the storage medium. The thesis work begins with a systematic review comparing the clinical success rates of resin composite restorations in posterior teeth, over two time periods, namely 1995-2005 and 2006-2016. It was shown that the main failure reasons for posterior resin composite restorations changed slightly over these periods, with factors related to the material and tooth becoming more significant in the later period, although recurrent caries remained an important reason for failure. Based on the broad findings of the review, three laboratory-based projects were designed to examine the physical properties of resin-based composites, focusing on the recent bulk-fill restorative materials. The experiments also included the effects of polymerising light-curing units, since the new high irradiance (light intensity) units recommend shorter curing times. In addition, a study on fracture toughness of glass -ionomer cements were conducted to determine whether a simple fracture toughness test would provide useful outcomes for a brittle material such as GIC and whether an ion-containing storage medium such as artificial saliva would influence outcomes. The results of these experiments indicated that variations in material composition and curing light devices had a significant influence on the physical properties such as curing stress shrinkage, the combined temperature of polymerisation and curing light radiant exposure (energy), and wear after thermal ageing. A final experiment investigated the effects of the polymerisation shrinkage on the movement of tooth cusps when the resin composite was exposed to two different irradiances curing light devices. This experiment showed that the high irradiance produced greater and more rapid cuspal movement and a greater rise in temperature within the pulp chamber. The results probably cannot provide a direct translation to the clinical situation. However, it would seem that the use of bulk-fill resin composite materials needs to be managed more carefully than perhaps what has been recommended by manufacturers of such materials.
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ItemThe development of a biodegradable nano-particle vaccine delivery system( 2019)Despite the recent advances in cancer treatment, this disease continues to pose a serious threat to public health. Nanoparticle-based delivery platforms have been shown to be a promising strategy for cancer immunotherapy. Therapeutic cancer vaccines are designed specifically to elicit a potent adaptive immune response, giving rise to the specific eradication of cancer cells. Among the different synthetic nanoparticle carriers currently available calcium phosphate nanoparticles (CaP NPs) are the most promising potential vaccine transporters, and have attracted increasing attention during the past decade. In this thesis, the synthesis of a novel CaP NP vaccine is described and the further investigation of their effects on immune cells is examined. In this study, a novel citrate chelation method for CaP NP synthesis was developed to obtain well-defined, homogeneous NPs. The method of synthesis is innovative, convenient, inexpensive and, most significantly, consistent and reproducible. Additionally, this study is the first investigation to describe the effect of different types of calcium and phosphate salts on NP synthesis. It was found that various sizes of CaP NPs can be obtained by using different calcium and phosphate salts to synthesise the nanoparticles. To further develop the formulation of the nanoparticle vaccine, a layer-by-layer approach to vaccine synthesis was utilised. All experimental parameters of the layer-by-layer approach of nanoparticle formulation were optimised during synthesis to avoid NP aggregation and to increase NP size stability. Significantly, it was found that cross-linking the protein antigen on the NP surface-enhanced salt stability and greatly reduced the host-plasma protein adsorption on to the NP. Moreover, the composition of the protein corona identified by mass spectrometry showed the major component of bound protein was albumin. To study the impact of NP size on the interactions between NPs and host cells three sizes (170 nm, 260 nm and 360 nm) of rod-like shaped NPs were used in vitro, and the effects on epithelial cells and macrophages were observed. This study demonstrated that the three sizes of NPs used in this study can efficiently bind to epithelial cells and migrate through the epithelial barrier and that they induce a cytokine profile from epithelial cells favouring the recruitment of further immune cells. Moreover, the three sizes of cross-linked CaP-PEI-OVA NPs are phagocytosed by RAW 264.7 cells in a dose-dependent manner. Significantly, large CaP NPs induced significantly stronger cell-binding, cellular-uptake, phagocytosis, NF-kappa-B activation, cytokine secretion, and inflammatory cell surface marker expression at the highest NP to cell ratio than the smaller nanoparticles. Finally, a new potential adjuvant with favourable chemical properties for use in vaccine applications was designed and synthesised. A TLR2 ligand, Pam2KK4CG, was synthesised and conjugated to three sizes of calcium phosphate OVA NPs. The effect of these functionalised NPs on macrophages was compared to commercially available Pam3CSK4 and Palmitoyl alone. It was shown that the particles were biocompatible with macrophages and that they were phagocytosed by RAW 264.7 cells in a dose-dependent manner. Additionally, the functionalised NPs significantly increased the expression of cell surface markers (CD40, CD80, and MHC II) in RAW 264.7 cells. Finally, the expression of cytokines was greatly enhanced by Pam2KK4CG lipopeptide treatment as compared to CaP-OVA NPs alone. Taken together, the results presented in this thesis provide an in-depth understanding of the immune response of epithelial cells and macrophages to a synthesised CaP NPs vaccine. Because these cells are vital for the induction of the adaptive immune responses, further work arising from the results of this study may make a significant contribution to the development of therapeutic vaccines for the treatment of cancer.
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ItemSurgical Management of Recurrent Temporomandibular Joint Dislocation - Systematic Literature Review and Development of a Treatment Protocol( 2019)Recurrent TMJ dislocation is a rare entity, clinically distinct from acute or chronic dislocation. It is associated with significant morbidity and deterioration to quality of life for affected patients. Recurrent temporomandibular joint (TMJ) dislocation can be challenging to treat and current understanding regarding aetiology and management of this condition is limited. The aim of this thesis was twofold. The first was to conduct a systematic review regarding the current understanding of managing recurrent TMJ dislocation. The second aim was to review the surgical management and long-term outcomes of patients with recurrent TMJ dislocation who presented to a single Hospital Department over a period of six years so as to formulate a practical treatment algorithm. A retrospective review of cases surgically managed for recurrent TMJ dislocation was undertaken with respect to patient demographics, clinical features, surgery provided, and long term follow up. A literature review was conducted using PRISMA guidelines to identify papers published between 2006 and 2016. The resultant papers were analysed. A total of 33 papers were found relevant to the study. Minimally invasive techniques described included autologous blood injection, which was associated with an overall success of 80% at 12 months. Other modalities investigated included OK-432 sclerotherapy, laser capsulorrhaphy, botulinum toxin of the lateral pterygoid muscle or modified dextrose. These publications show promising success rates. Surgical techniques described included disc plication, eminoplasty and eminectomy. These modalities had a similar success rate, although numbers were limited. For the second part of this thesis, a total of 14 patients were identified who were managed for recurrent TMJ dislocation over a 6-year period from 2010 to 2016. The cases were followed up for a minimum of 12 months and a maximum of seven years. Results showed effective long-term resolution of symptoms using a combination of eminectomy, disc plication (meniscopexy) and where clinically indicated, lateral pterygoid myotomy. This thesis found that the true incidence of recurrent TMJ dislocation is unknown and aetiology is limited to expert opinion. The current understanding of management for recurrent TMJ dislocation is limited to case series and case reports. This thesis compiles the current understanding of management of recurrent TMJ dislocation. A decision making algorithm, with a personalised, step-wise approach to treatment is presented. The retrospective review portion of the thesis has shown that a combination of eminectomy and disc plication (meniscopexy) is effective in providing long term positive outcomes in the surgical management of recurrent TMJ dislocation. Those cases of recurrent TMJ dislocation resulting from dystonia of the lateral pterygoid muscle also benefitted from additional lateral pterygoid myotomy.
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ItemImmune Cell Phenotypes in Chronic Periodontitis( 2019)Chronic periodontitis (CP) is a polymicrobial immune-inflammatory disease affecting the supporting structures of a tooth. If left untreated, it leads to eventual tooth loss and loss of function in the oral cavity. The immune-inflammatory component of disease is complex with both the innate and adaptive immune systems involved in disease pathogenesis. Thus, the aim of this study was to phenotype the longitudinal variation in neutrophil and T cell subsets in peripheral blood of chronic periodontitis patients following treatment. Fifty four patients with CP and 40 healthy controls were recruited for the study. Peripheral blood mononuclear cells (PBMCs), saliva and subgingival samples were collected from CP patients at baseline, 3-, 6- and 12-months post-treatment and once from healthy controls. Subjects were assessed by timepoint as well as treatment outcomes. Treatment outcome groups were dependent on the prevalence of sites with PD greater than or equal to 5 mm at the end of the study period where the good treatment outcome group had less than or equal to 10 percent of sites, moderate treatment outcome group had between 10 - 20 percent of sites and the poor treatment outcome group had greater than or equal to 20 percent of sites with PD greater than or equal to 5 mm. The various cells subsets and cytokines were correlated to periodontal parameters. In addition, differences were also assessed between smokers and non-smokers. The periodontal parameters, mean probing depth (PD) and percentage of sites with bleeding on probing (BOP) were increased at all timepoints in CP compared to health and decreased at all subsequent timepoints compared to baseline. Upon separation into treatment outcome groups, patients with poorer treatment outcomes, initially had increased mean PD. In addition, smokers had less BOP at baseline and a decreased response to treatment as seen by a lower reduction in PD at 3-months post-treatment compared to non-smokers. Innate immune responses were examined by assessing surface expression of CD11b, CD16b, CD62L and CD11b. CD62L was associated with treatment-related changes, however, treatment did not affect immature and mature neutrophils proportions. Subsets of immunologically suppressive and normal neutrophils displayed a reciprocal relationship with treatment where suppressive neutrophils decreased and normal neutrophils increased at 3- and 6-months compared to baseline. The red complex bacteria showed a reduction with treatment, however, they were persistently recovered from periodontitis patients at all timepoints in comparison to health. In addition, P. gingivalis was significantly increased in CP compared to health in the poor treatment outcome group. This reduction in red complex bacteria was reflected by a change in the CD4, CD8, CD4+CD8+ and CD4-CD8- T memory cell profile. Naive T cells were decreased in CP at baseline and increased with treatment, while central and effector memory T cells were increased at baseline and decreased with treatment. Poorer treatment outcomes were associated with no changes in the CD4 and CD8 effector memory cells. Examination of cytokine producing effector and regulatory T cell subsets indicated that TCRalphabeta+CD4+ and TCRalphabeta+ cells were the major sources of IFN-gamma and IL-4 in PBMCs, while TCRalphabeta+CD4+ cells were the major cell sources of Foxp3 and IL-17 expressing cells. A reduction in IFN-gamma expressing cells and an increase in Foxp3 expressing cells at 12-months compared to baseline were associated with good treatment outcomes while no changes with treatment were associated with poor treatment outcomes. In vitro expression of IFN-gamma, IL-4, IL-17 and IL-10 upon no stimulation and stimulation with P. gingivalis and concanavalin A was also evaluated in PBMCs. IL-10 was the largest cytokine produced upon P. gingivalis stimulation, followed by IFN-gamma. IFN-gamma and IL-17 expression was significantly decreased in CP at baseline compared to health, while IL-10 and IL-4 levels were not significantly different. In addition, treatment of CP was associated with a reduction in IFN-gamma and IL-4 levels compared to baseline upon P. gingivalis stimulation. Lastly, fifteen T helper 17 cell-related cytokines were evaluated in serum and saliva. IL-1beta, IL-6, sCD40L and TNF-alpha in serum and IL-1beta, IL-6, IL-25 and IL-31 in saliva were significantly increased at baseline compared to health and decreased with treatment. In contrast, serum IL-31 was significantly decreased at baseline compared to health and increased with treatment. In addition, salivary IL-10, IL-17A, IL-17F IL-23, IL-33, IFN-gamma and TNF-alpha also displayed treatment-related reduction. Correlation networks showed that cytokines in saliva showed an increased number of correlations compared to serum. Smoking had an effect on selected immunological subsets. In general, smokers had increased proportions of neutrophils and naive T cells and decreased effector memory T cells and effector memory T cells re-expressing CD45RA. In addition, smokers also displayed aberrant responses in Foxp3 and IL-10 expressing cells in PBMCs as well as IL-1beta and IL-17 cytokine production in serum and saliva. This is a comprehensive longitudinal study of both innate and adaptive changes associated with treatment of CP and compares cell phenotypes across a range of clinical responses to treatment. In particular, this study is the first to report longitudinal variation in suppressive neutrophils, memory T cells, production of four canonical T cell cytokines in PBMCs in response to P. gingivalis and assessment of salivary IL-25, IL-33 and sCD40L as well as IL-31 in serum and saliva in chronic periodontitis. Moreover, this study also showed that good treatment outcomes were associated with treatment-related variation in some memory and T cells subsets, whereas poor treatment outcomes were not. The results from this study provide a preliminary understanding of key modulators of the immune-inflammatory response and furthers our knowledge of the aetiopathogenesis of periodontal disease.