A thesis submitted to fulfill the requirements for the degree of Doctor of Dental Science

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The Giant Cape zebra Equus capensisis one of the most iconic fossil herbivore species of the South African Quaternary. It is widely believed to have persisted relatively unchanged in its morphology for the duration of its existence, that encompassed the mid-to late Pleistocene. Described as a large-bodied equid, its skeletal remains were originally regarded as distinct and readily distinguishable from those of other fossil equids, especially with respect to their large size. This applied particularly to its cheek teeth, that were described as large with unique occlusal enamel morphology. Palaeontologists have generally accepted the taxonomic status of E. capensis without question. However in reality, its taxonomic status is far from incontrovertible as many of its definitive morphological traits are based on conjecture. Equus capensis was originally described on the basis of a large mandible embedded in limestone that had much of its dental row obscured. The rest of it was reconstructed using unassociated, usually isolated osteological elements from a variety of localities. Perhaps not surprisingly, apart from size, researchers have struggled over the years to distinguish between E. capensis skeletal elements and those of other fossil equids. An ancient DNA study of four E. capensis teeth further compounded the uncertainty around its taxonomic status by exposing a high degree of genetic similarity to E. quagga. The present study represents the first systematic investigation of morphological traits originally used to define E. capensis. Specifically, it considers dental occlusal enamel form and function to help shed light on the taxonomic status of E. capensis. Geometric morphometrics was used to compare premolar and molar occlusal enamel pattern in E. capensis and a large comparative equid sample. This was followed by an evaluation of levels of enamel complexity. Next, traditional linear methods were used to compare overall occlusal dental form. Finally, meso wear analysis was used to evaluate dental function. Analyses of dental occlusal enamel form were able to distinguish E. capensis teeth from those of equids in the comparative sample on the basis of size, but not shape. This result is telling since the shape of dental occlusal enamel bands carries greater taxonomic significance than their size. Size is easily influenced by environmental factors and may fluctuate through time. Also, analyses of mesowear patterns were unable to separate E. capensis teeth from those of E. quagga, with which it is thought to have co-occurred. Overall the results of this study do not support the legitimacy of E. capensisas as a taxon and lays the ground for additional enquiries.

Ce travail a été réalisé dans le cadre d’une collaboration entre le laboratoire de Chimie-Métallurgie de l’INSA de Rennes et le laboratoire de biomatériaux en site osseux (LBSO) de la Faculté de Chirurgie Dentaire de l’Université de Rennes1. L’alliage de titane de type β Ti-27Nb (% at.) a été nitruré pour des applications en implantologie orale parce qu'il possède un bas module d'élasticité, proche de celui de l’os et qu’il est composé uniquement d'éléments biocompatibles. Dans un premier temps l’alliage Ti-27Nb a été synthétisé grâce à un four à induction magnétique selon la technique de fusion en lévitation en creuset froid sectorisé. Un traitement de surface par nitruration en phase gazeuse a ensuite été effectué pour augmenter sa résistance à la corrosion et à l’usure. L’analyse structurale a été réalisée par DRX et par des observations en microscopies optique et électronique à balayage. L’analyse chimique a été effectuée par spectrométrie à dispersion d’énergie. La topographie et la dureté superficielle ont été caractérisées par AFM et par nano-indentation. Des essais tribologiques ont permis d’évaluer le coefficient de frottement et la résistance à l’usure. Pour la caractérisation mécanique des essais de traction conventionnels et cycliques ont été effectués. La biocompatibilité a été évaluée in vitro par des cultures bidimensionnelles de plusieurs populations cellulaires en contact des implants métalliques : ostéoblastes, fibroblastes et cellules épithéliales. Elle a été déclinée en termes de cytotoxicité, de prolifération cellulaire, d’expression génique et de morphologie cellulaire. Les propriétés de l’alliage Ti-27Nb nitruré sont particulièrement intéressantes pour une implantation durable en site osseux. / This work was performed in collaboration with the Metallurgical Chemistry team of the Institute of Chemical Sciences of Rennes and the Biomaterials Laboratory of the Faculty of Dentistry of Université de Rennes1. The low modulus Ti-27Nb (at. %) alloy with non-toxic elements was nitrided for the first time in this study for dental implant applications. The alloy was firstly synthetized by cold crucible levitation melting technique. A high temperature gas nitriding treatment was then carried out in order to improve the wear and corrosion resistance. The structural analysis was performed by X-ray diffraction and the microstructure was observed by optical microscopy and by scanning electron microscopy. The chemical analysis was performed by Energy Dispersion Spectrometry. Superficial mechanical properties were then studied by nano-indentation and ball-on-disc tribological tests. Conventional and tensile tests were realized. The biocompatibility was evaluated by in vitro tests performed on human osteoblasts, fibroblastic cells and epithelial cells. Cell proliferation and differentiation were studied as well as cell morphology. All of the observed properties make the nitrided Ti-27Nb alloy particularly suitable for enhanced longevity of dental implants.

Thesis (M.S.)--University of Michigan, 2001. / Includes bibliographical references.

Thesis (M.D.S.) -- University of Adelaide, Dept. of Dental Science, 1965. / Typescript.

Made available in DSpace on 2014-08-20T14:30:15Z (GMT). No. of bitstreams: 1 Dissertacao_Carolina_Camporese_Franca_Pinto.pdf: 1194614 bytes, checksum: 3e427b619208da3e88e0c1ce57f53f1f (MD5) Previous issue date: 2011-06-28 / The aim of this study was to perform a systematic review of prevalence of black stains and their association with dental caries. Also, this study aimed to estimate the prevalence of dental black stains from a cohort of children born in 2004 in Pelotas, RS, Brazil, evaluating the association with dental caries. For the systematic review, the following electronic databases were accessed: Cochrane Central Register of Controlled Trials, Web of Science, EMBASE, MEDLINE, PubMed, LILACS, BBO. No language restriction was used and the combinations of the following keywords were used: prevalence, black stain teeth, black tooth stain, and their equivalents in Portuguese. The search was limited to studies in children and adolescents with deciduous and permanent teeth, and all studies showing prevalence of black stains were included. The selection of studies was done by three reviewers independently. The cross-sectional study included a sample of 1129 five years old children belonging to the Pelotas birth cohort. Children were visited to carry out examination and a questionnaire including questions about demographics conditions, habits and behaviors related to oral health. Clinical examination included assessment of the presence or absence of black stains and presence of caries by DMFT. Logistic regression was used to analyze the data.The prevalence of black stains was 3.5% (95% CI 2.5 to 4.7), and the prevalence of caries was 48.4% (95% CI 45.4 to 51.4). Black stains and decay were more prevalent in light or dark-skinned black children, in those from mothers with lower level of education and low income level. Adjusted analysis revealed that the presence of black stains was associated with lower levels of dental caries (OR=0.51; 95% CI=0.26-0.99; p=0.048). Considering the results from the systematic review, 129 papers were found from the search with the keywords, and nine met the established inclusion criteria. The prevalence of black stains found in the studies was 10.4% (95% CI 6.8 to 14.1) for permanent teeth, and 4.0% (95% CI 0.43 to 7.5) for deciduous teeth. From the selected studies, five showed lower caries experience in individuals with black stains on the teeth. Conclusions: Based on the analysis of the reviewed studies and considering the data from the cross-sectional study conducted, it is suggested that the diagnosis of black stains should be based on the presence of black spots and / or the formation of linear pigmentation round the gingival margin and / or diffuse the dental crown, and these patches must be difficult to remove, and must be present in at least two teeth. Dark stains can be considered a condition of protection to tooth decay, but studies must be conducted so that the determinant of the black stains and therefore the actual protective factor is known and further explored / O objetivo do presente estudo foi realizar uma revisão sistemática sobre prevalência de manchas negras e associação com cárie dentária; e estimar a prevalência de manchas negras dentais em crianças pertencentes à coorte de nascimentos de 2004 de Pelotas, RS-Brasil, avaliando a sua associação com cárie dentária. Para a revisão sistemática, as seguintes bases eletrônicas de dados foram acessadas: Cochrane Central RegisterofControlledTrials, ISI Web of Science, EMBASE, Medline, PubMed, LILACS, BBO. Não houve restrição de idioma e foram utilizadas combinações entre as seguintes palavras-chave: prevalence, blackstainteeth, blackstaintooth, e seus correspondentes na língua portuguesa.A pesquisa foi limitada a estudos em crianças e adolescentes com dentição decídua e permanente, e para serem incluídos, deveriam conter dados sobre a prevalência de manchas negras. A seleção dos estudos foi feita por três avaliadores de forma independente. O estudo transversal abrangeu uma amostra de 1129 crianças pertencentes à coorte de nascimentos de Pelotas. As crianças foram visitadas para realização de exame bucal e aplicação de questionário incluindo questões demográficas e sobre hábitos e comportamentos relativos à saúde bucal. O exame clínico incluiu avaliação da presença ou ausência de manchas negras e presença de cáries através do índice ceo-d.Regressão logística foi utilizada para analisar os dados. A prevalência de manchas negras foi de 3,5% [(IC 95% 2,5-4,7)], e a prevalência de cáries foi 48,4% (IC 95% 45,4-51,4). Manchas negras e cáries foram mais prevalentes em mulatos e negros, em filhos de mães com menos anos de estudo, assim como em filhos de mães de baixa renda.A análise ajustada para fatores confundidores revelou associação entre manchas negras e baixos níveis de cárie (OR=0,51; IC 95%=0,26-0,99; p=0,048). Os resultados desse estudo sugerem que a presença de manchas negras é fator de proteção para cárie dentária. Considerando os resultados da revisão sistemática realizada, foram encontrados 129 artigos a partir das palavras-chave utilizadas, e destes, noveatenderam os critérios de inclusão estabelecidos. A prevalência média de manchas negras encontrada nos estudos foi 10,4% (IC 95% 6,8-14,1) para dentes permanentes, e 4,0% (IC 95% 0,43-7,5) para dentes decíduos. Dos artigos selecionados, cinco evidenciaram menor experiência de cárie em indivíduos com manchas negras nos dentes.Conclusões: A partir da análise dos artigose considerando os dados do estudo transversal realizado, sugere-se que o diagnóstico de manchas negras deve ser baseado na presença de pontos negros e/ou na formação de pigmentação linear contornando a margem gengival e/ou difusos pela coroa dentária, e estas manchas devem ser de difícil remoção, e devem estar presentes em no mínimo dois dentes. As manchas negras podem ser consideradas uma condição de proteção para cárie dentária, no entanto estudos devem ser conduzidos para que o fator determinante das manchas e consequentemente o real fator protetor seja conhecido e melhor explorado

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

Thesis (M.S.)--University of Michigan, 1992.

Thesis (M.S.)--University of Michigan, 1996. / Includes bibliographical references.