Le développement dentaire est essentiellement étudié chez la souris, modèle mammifère le plus commun en biologie. Cependant, contrairement à la majorité des mammifères, les souris ne remplacent pas leurs dents. Ainsi, les mécanismes impliqués dans le remplacement dentaire mammalien sont encore inconnus. Au cours de cette thèse, nous nous sommes intéressés au développement et remplacement dentaire mammalien en utilisant le lapin Oryctolagus cuniculus comme modèle d’étude. Le lapin étant déjà séquencé, utilisé en recherche biomédicale avec une période de gestation courte et remplaçant ses dents, il semblait être un modèle pertinent en odontologie. Le lapin était un modèle méconnu du point de vue du développement dentaire, nous avons donc d’abord réalisé une étude histo-morphologique afin de caractériser la mise en place des dents déciduales et permanentes. Des reconstructions 3D des tissus mous ont été réalisés à différents stades embryonnaires afin d’obtenir une chronologie du développement et remplacement dentaire. Cette chronologie commence aux premières observations morphologiques de l’initiation du développement des premières dents jusqu’à la minéralisation des dernières dents à se développer.Puis, suite à l’identification dans la bibliographie de gènes candidats potentiellement impliqués dans le remplacement dentaire, nous avons étudiés les profils d’expressions de ces gènes afin de mieux comprendre la régulation spatio-temporelle du remplacement dentaire chez le lapin. Nous avons ensuite replacé nos résultats sur le développement chez le lapin dans un contexte évolutif. Ainsi, nous avons réalisé une étude d’anatomie comparée chez les lagomorphes actuels et quelques fossiles afin d’identifier des variations morphologiques dentaires au cours de leur histoire évolutive. Nous nous sommes particulièrement intéressé à la mise en place des cuspides au cours de l’odontogénèse ainsi qu’aux variations de la surface occlusale des dents supérieure tout au long de la vie des lapins et autres lagomorphes. En comparant les variations au cours de l’évolution avec celles observées lors de l’ontogénie dentaire chez le lapin nous avons identifié des processus d’hétérochronies du développement. Nous avons ainsi montré que la molaire actuelle du lapin suit un processus de péramorphose, donc de surdéveloppement, en comparaison aux lagomorphes fossiles. Le lapin est ainsi un modèle animal prometteur en biologie du développement et en évolution afin de mieux comprendre la mise en place du remplacement dentaire mammalien ainsi que les variations de forme dentaire au cours de l’évolution des mammifères. / Tooth development is essentially studied in mice, the favorite mammalian model in biology. However, mice do not replace their teeth on contrary to numerous mammals. So, the mechanisms involved in mammalian tooth replacement are still unknown. In this thesis, we focused on mammalian dental development and replacement using the European rabbit Oryctolagus cuniculus as animal model. The European rabbit is already sequenced, used in biomedical field, has a short gestation time and replaced its teeth, so rabbit seemed to be a relevant model in dental research.Rabbit dental development was not defined, so we first performed a histo-morphological study to characterize the development of deciduous and permanent teeth. 3D soft tissue reconstructions were performed at different embryonic stages to obtain a chronology of tooth development and replacement. This chronology begins with the first morphological observations of the initiation of the development of the first tooth until the mineralization of the last tooth to develop.Then, we identified in the bibliography candidate genes potentially involved in dental replacement. We studied the expression profiles of these genes in order to better understand the spatio-temporal regulation of tooth replacement in rabbits.We then returned our results to rabbit development in an evolutionary context. Thus, we performed a comparative anatomy study in the current lagomorphs and some fossils in order to identify dental morphological variations during their evolutionary history. We were particularly interested in the setting of cusps during odontogenesis as well as in the variations of the occlusal surface of the upper cheek teeth throughout the life of rabbits and other lagomorphs. Comparing changes during evolution with those observed during dental ontogeny in rabbits allow us to identify heterochronous processes of development. We have shown that the current molar rabbit follows a process of peramorphosis, so an overdevelopment compared to fossil lagomorphs.The rabbit is thus a promising animal model in developmental and evolutionary biology to better understand the implementation of mammalian tooth replacement and tooth shape variations during mammalian evolution.

[pt] Esta dissertação apresenta resultados de simulação física e numérica do comportamento mecânico de cavidades circulares em meios contínuos. Na simulação numérica foi possível reproduzir o comportamento tensão-deformação registrado nos ensaios. O comportamento mecânico do contínuo foi abordado de duas formas: i) Teoria clássica e ii) Modelo generalizado de Cosserat. A segunda abordagem, por dispor de um grau de liberdade extra, permite a reprodução numérica de algumas feições observadas ao redor das cavidades circulares em testes de laboratório de maneira mais realística. A teoria clássica de contínuo foi associada somente ao modelo constitutivo de Mohr-Coulomb. Já para Cosserat, foram utilizados dois modelos constitutivos: Mohr-Coulomb e Bogdanova-Lippmann Modificado. A motivação para apresentar contínuo generalizado neste trabalho é que o mesmo inclui a parcela referente ao comportamento das partículas. Em todos os testes foram utilizadas amostras do arenito Botucatu, obtidas em São Paulo e Paraná. Para caracterização mecânica deste material foram realizados ensaios uniaxiais, triaxiais e brasileiros. Já a simulação física do comportamento de cavidades circulares foi analisada segundo duas geometrias: cúbica (com aplicação de estado de tensão biaxial) e cilíndrica (TWC – Thick Walled Cylinder). O acompanhamento da ruptura das cavidades cilíndricas foi feito de forma visual (amostras cúbicas) e com monitoramento tomográfico em tempo real (amostras cilíndricas). Com base na observação experimental da ruptura das cavidades cilíndricas e nas simulações numéricas considerando o contínuo clássico e de Cosserat, foi possível verificar que, ambas as abordagens possibilitaram a reprodução das feições observadas. / [en] This work seeks to realize physical and numerical simulation of the mechanical behavior of the wellbore stability for continuum environment.The Continunm s mechanical behavior is approach by two ways: i) Classic Continuum Theory and ii) Cosserat Continuum. On the second approach, the theory allows an extra degree of freedom, which plays an important rule on instabilities and bifurcation problems; this allows a more realistic numerical simulation of the failure mechanism observed on circular cavity. The Classic Continuum Theory is associated to a Mohr-Coulomb constitutive model. On the other hand for Cosserat Theory s applied tow constitutive models: Mohr-Coulomb and Modified Bogdanova-Lippmann.The generalized continuum takes in account the microstructure of the material.It s used on all tests Botucatu s specimens, which were acquired at São Paulo and Paraná. For characterize the rock s behavior it s realized triaxial, uniaxial and brazilian tests. Then the physical simulation of the circular cavity s behavior was analyzed for two geometries: cubic samples (biaxial stress) and cylindric samples (TWC – Thick Walled Cylinder). The failure mechanism of circular cavity was followed visually (cubic samples) and with CT X-Ray in real time (cylindric samples).From the experimental observations of the failure mechanism of circular cavity and numerical simulations, with Classic Continuum and Cosserat, was possible to verify that both approaches reproduce the behavior of the rocks observed on experimental data.