The overall aim of this thesis was to examine the kinetics of proton-promoted dissolution of the dental hard tissue enamel as a non-bacterial process and the evaluation of inhibitors with the intent of minimising the dissolution process and effectively protecting the surface. A novel approach was taken, utilising scanning electrochemical microscopy (SECM) to galvanostatically generate controllable and well defined proton fluxes in defined areas of the surface. The resulting etch pits formed on the surface were characterised by optical microscopy and white light interferometry (WLI), which quantitatively determined etch pit dimensions. A theoretical finite element model (FEM) was used to elucidate the kinetics of dissolution based upon the analysis of the shape and dimensions of etch pits produced. A heterogeneous rate constant of dissolution of 0.08 ± 0.04 cm s-1 was attributed to untreated enamel, whereas 2 min treatment with 1000 ppm sodium fluoride (NaF) decreased this rate constant slightly to 0.05 ± 0.03 cm s-1. The impact of fluoride on the rate of proton attack was evident from the formation of shallower broader etch pits. In relation to both acid erosion and caries, the two most relevant acids pertinent to enamel dissolution are citric acid and lactic acid. These acids were investigated by protonating their respective sodium salts in-situ to produce localised weak acid directly under the probe tip. This permitted the surrounding enamel sample to remain largely unaltered giving a true surface for comparison, whilst allowing evaluation of the kinetics in the presence of each weak acid. Etching in the presence of lactic acid, showed a surface controlled process with a rate constant of 0.1 ± 0.03 cm s-1. Etching in the presence of the triprotic citric acid, also yielded a surface controlled process with a rate constant of 0.35 ± 2.6 cm s-1. Calcite was also investigated using SECM, WLI and FEM to validate the use of these techniques. The kinetic data extrapolated was comparable to rate constants found in literature, confirming the validity of these methods. In this case, a novel approach was the use of experimental data to parameterise the finite element model directly. Confocal laser scanning microscopy (CLSM) coupled with SECM was used to visualise proton fluxes from the tip of the UME. This allowed, not only, correlation of the current applied to the probe tip with the pH, but also quantitative data on the spread of protons across a particular surface. Rate constants found for untreated and fluoride-treated enamel were comparable to those found in SECM etching, however, zinc ion treatment proved to result in much greater inhibition of dissolution than fluoride.

Titanium (Ti) dental implants are a successful treatment modality to replace missing teeth. Success is traditionally defined as the retention of the Ti dental implant but fails to account for peri-implant inflammatory diseases such as peri-implant mucositis and peri-implantitis. Peri-implant diseases are caused by the formation of pathogenic bacteria biofilms on the implant surface and disease progression can lead to dysfunctional and unaesthetic outcomes. There is no universally accepted treatment or management protocol for peri-implant disease. The objectives were to develop methods to prevent bacterial adhesion to Ti implant surfaces or treat existing biofilms. The relationship between bacterial adhesion of common early coloniser bacteria and topological features on dental implant surfaces was studied. Reproducible model systems were identified to be used in studies of biofilm formation and disruption. Early bacterial adhesion was investigated on engineered Ti surfaces created using Scanning-Laser-Melting or on Ti nanotubule surfaces. Photoactivation of Ti oxide films was investigated on thermally or anodically oxidised Ti and demonstrated the potential to pre-treat implant surfaces to reduce bacterial attachment. Finally chemical disinfection of Ti surfaces with a novel Eucalyptus Oil (EO) based formulation was demonstrated to increase the permeation of bactericidal agents into immature biofilms formed on Ti surfaces.

This investigation was aimed at measuring the changes in dielectric properties of glass ionomer cements during their setting reaction in order to observe if there is a correlation between these properties and the cement curing. Commercial glass ionomer cements were prepared and their setting process was monitored over a 24 hour period using FT-IR and direct contact impedance measurement. An impedance bridge with a dielectric test assembly, based on previous work by Braden et al, was used to measure the dielectric properties of a number of different glass ionomer cements using a simple design. Using the dielectric properties of the glass ionomer cements, it could be possible to develop a micro-electro-mechanical sensor (MEMS) based on this design, which could be implanted into a dental restoration and interrogated remotely. During the curing of the cements examined, the dielectric data collected from the co-planar assembly showed a change in impedance over the course of the setting of the cement, which when compared to FT-IR spectra over the same period, showed a correlation between the dielectric properties and the chemical changes within the cement.

No description available.

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.

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.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This research considers the theme "Chemistry in Dentistry" as a starting point for the contextualization of chemical content, in order to contribute to the Chemistry teaching and learning process to 3rd year high school students of a public school in the city of Santa Maria, RS. In dealing with the chemistry involved in common materials of dental practice, as well as in common problems of oral health and aspects of prevention and treatment, Chemistry in Dentistry aims to the Social Chemical Theme "Oral Health", that has already been presented in Chemistry teaching in other works of our research group, LAEQUI. In this research, several interventions were developed, which allowed the structuring of its implementation in three stages: the first corresponds to the presentation of the theme to the students, and the others correspond to the two thematic workshops, guided by Three Pedagogical Moments. The development of these workshops seeks, besides to contextualize chemical content from the theme "Chemistry in Dentistry", to contribute to civic education of students, encouraging them to reflect on their habits regarding oral health and lead them to the perception that chemical knowledge can help to understand the causes of oral health problems, as well as prevention and treatment of these. In the thematic workshops are inserted experimental activities, the didactic game and the case studies as methodological strategies to relate chemical content with the daily life of students from the perspective of the theme, beyond the study of concepts. For data collection, instruments such as questionnaires, exercises, textual production and log books (records notebooks, both the researcher as students) were used and analyzed according to the Discursive Textual Analysis. The results allow us to conclude that the theme Chemistry in Dentistry associated with the use of different teaching methodologies, such as thematic workshops, provided an approximation of Chemistry with the daily life of students, promoting the teaching and learning process of chemical content and their civic education. / Esta pesquisa considera a temática Química na Odontologia como ponto de partida para a contextualização de conteúdos químicos, a fim de contribuir para o processo de ensino e aprendizagem de conteúdos de Química para estudantes de 3ª série do Ensino Médio de uma escola estadual da cidade de Santa Maria, RS. Ao tratar da Química envolvida em materiais comuns na prática odontológica, bem como ao abordar problemas comuns de saúde bucal e aspectos de sua prevenção e tratamento, a Química na Odontologia tem alcance para o Tema Químico Social Saúde Bucal , já apresentado no ensino de Química em outros trabalhos de nosso grupo, o LAEQUI. Nesta pesquisa, foram elaboradas várias intervenções, as quais permitiram a estruturação de sua aplicação em três etapas: a primeira corresponde à apresentação da temática aos estudantes, e as outras duas correspondem às duas oficinas temáticas desenvolvidas, orientadas pelos Três Momentos Pedagógicos. O desenvolvimento destas oficinas busca, além de contextualizar conteúdos químicos a partir da temática Química na Odontologia , contribuir para a formação cidadã dos estudantes, incentivando-os a refletir sobre seus hábitos com relação à saúde bucal, bem como conduzí-los à percepção de que os conhecimentos químicos podem auxiliar tanto a compreender as causas dos problemas de saúde bucal, bem como a prevenção e o tratamento destes. Inseridas nas oficinas temáticas, estão as atividades experimentais, o jogo didático e o estudo de casos como estratégias metodológicas para relacionar conteúdos de química com o cotidiano dos estudantes sob a perspectiva da temática, para além do estudo de conceitos. Para a coleta de dados, instrumentos como questionários, exercícios, produção textual e diários de bordo (cadernos de registros, tanto da pesquisadora como dos estudantes) foram utilizados e analisados segundo a Análise Textual Discursiva. Os resultados obtidos nos permitem concluir que a temática Química na Odontologia , associada ao uso de diferentes metodologias de ensino, como as oficinas temáticas, proporcionou uma aproximação da Química com o cotidiano dos estudantes, favorecendo o processo de ensino e aprendizagem de conteúdos químicos e a formação cidadã dos mesmos.