Dissertations / Theses on the topic 'Chemistry in dentistry'

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Advanced Dental Biomaterials is an invaluable reference for researchers and clinicians within the biomedical industry and academia. The book can be used by both an experienced researcher/clinician learning about other biomaterials or applications that may be applicable to their current research or as a guide for a new entrant into the field who needs to gain an understanding of the primary challenges, opportunities, most relevant biomaterials, and key applications in dentistry.

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.

A limiting factor in the digitization of dental devices is the availability of materials suitable for use in both dentistry and the new digital technologies. As a rapidly growing industry, three-dimensional printing (3DP) has the potential to disrupt traditional manufacturing and prototyping methods. A review of both restorative materials and the current 3DP materials has lead to a focus on fiber- reinforced composites in the exploration for a new 3DP material. In addition, another area worth exploring and investing in would be 3D bioprinting as it opens up the possibility of regenerative dentistry.

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.

This thesis examines the development of a novel in vitro biological caries model and its suitability in testing the efficacy of anti-caries approaches. Dental caries remains a public health concern worldwide; with extensive treatment costs and impacts on quality of life. Ineffective removal of all dental plaque from tooth surfaces after brushing, the insufficient delivery of anti-caries therapies; along with continuing shifts towards high frequency, sucrose-rich food consumption, expedites the caries disease process. It is, therefore, important to explore caries risk and development at these sites, particularly when representatively assessing the efficacy of a test agent in preventing caries. This caries model enabled the study of the anti-caries effects of fluoride to assess its efficacy in conditions simulating the modern diet. The current methodology employed the Constant Depth Film Fermenter (CDFF) to investigate the caries disease process in response to fluoride delivered continuously; twice and thrice daily; and at different concentrations. The approach is the first in CDFF research modelling caries inclusive of a biologically relevant microcosm biofilm in addition to enamel demineralisation. Specific members of multispecies biofilm were selectively enumerated using traditional microbiological culture techniques whilst caries was simultaneously quantified with Transverse Microradiography (TMR), Quantitative Light-Induced Fluorescence (QLF), and Non-Contact Surface Profilometry (NCSP). The fluorescence of biofilm illuminated by QLF was also investigated. Results indicated that quantities of total or specific members of the microbial community are not direct indicators of caries risk and turning focus towards the metabolism of oral biofilm bacteria, and how it may be affected, is vital in caries research. TMR and QLF agree when quantifying caries whilst NCSP shows promise in studying surface changes. At 0.05 ppm, fluoride was unable to exert a significant anti-caries effect despite being continuously present during and between sucrose exposures. Laminated lesions confirmed the importance of maintaining elevated levels of fluoride in the oral environment throughout the day. At higher concentrations (1,450 and 228 ppm fluoride) the anti-caries efficacy of fluoride when supplied in frequent applications throughout the day was confirmed. A third application of fluoride did not appear to additively benefit enamel, since all strategies were effective after 10 days regardless of frequency. Nonetheless the increased plaque fluoride reservoir and subtle antimicrobial effects than in twice daily pulsed biofilm, mean the benefit of a third application is likely more discernible in the long term. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) elucidated significant calcium fluoride deposits of enamel surfaces beneath biofilm exposed to 1,450 ppm fluoride continuously. In conclusion, the CDFF can produce multispecies biofilm under conditions similar to those of the oral milieu and investigate its cariogenicity in response to diet and experimental anti-caries agents. The model could be examined using an array of techniques to obtain information about aspects of the biofilm, the substratum, and to validate upcoming methods in an orally representative environment. In this regard, the current study contributes not only to enamel caries research but to biofilm research in general by minimising variation.

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xxvi, 533 p.; also includes graphics (some col.) Includes bibliographical references (p. 259-292).

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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.

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A zircônia tetragonal estabilizada por ítria (Y-TZP) têm sido utilizada na área odontológica para próteses livres de metais devido à estética associada ao alto desempenho mecânico. Porém, a presença de ambiente úmido pode causar a transformação acelerada da fase tetragonal para monoclínica e consequente falha catastrófica deste material, processo este conhecido como degradação a baixa temperatura ou envelhecimento. A cinética desta transformação é função da composição química da cerâmica e sua microestrutura. Tendo em vista que métodos químicos permitem a síntese de pós cerâmicos à base de zircônia de dimensões nanométricas, cuja microestrutura da cerâmica sinterizada é constituída por grãos submicrométricos quimicamente homogêneos, e que a presença de alumina é indicada para evitar a degradação de fases da zircônia, o objetivo deste estudo foi verificar a degradação a baixa temperatura e ambiente úmido de cerâmicas de zircônia estabilizada com 3 mol% de ítria (Y-TZP) e do compósito Y-TZP/Al2O3, proveniente de pós sintetizados pela rota de coprecipitação. A concentração de alumina na Y-TZP foi estudada na faixa de 0,05 a 20% em massa. A eficiência do processo desenvolvido foi verificada pela avaliação das características físicas dos pós obtidos (granulometria, área de superfície específica, estado de aglomeração e estrutura cristalina). As amostras cerâmicas foram prensadas, sinterizadas e avaliadas quanto à densidade aparente e microestrutura. Após a caracterização inicial das cerâmicas a degradação das amostras foi estudada in vitro em reator hidrotérmico pressurizado a 150°C. As amostras (n=4) foram submetidas à análise de difração de raios X de acordo com o tempo de envelhecimento, acompanhando a curva cinética de transformação de fase. A porcentagem de cada fase cristalina foi determinada pelo Método de Rietveld. A relação entre o tempo de envelhecimento e a concentração de fase monoclínica foi determinada pela equação de Avrami modificada por Kolmogorow (Johnson-Mehl- Avrami-Kolmogorow JMAK). Após envelhecimento a 150°C por 70 horas, todas as amostras contendo alumina apresentaram menor concentração de fase monoclínica, comparativamente à cerâmica Y-TZP, que apresentou 66,5% dessa fase. Menores porcentagens de fase monoclínica após o envelhecimento hidrotérmico foram obtidas com a adição de 10 e 20% em massa de alumina na matriz de zircônia, sendo esses valores 59,1 e 52,9%, respectivamente. Deve-se considerar, no entanto, que a diminuição da degradação total é consequência da menor porcentagem de zircônia na matriz em função da adição de alumina. Neste contexto, o efeito benéfico da adição de alumina ocorre apenas no início do envelhecimento.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xix, 343 p.; also includes graphics (some col.) Includes bibliographical references (p. 325-343).