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Solutions matériaux et géométriques pour la réalisation de dispositifs médicaux implantables sur-mesure en alliages de titane : application aux implants endo-osseux et supra-osseux obtenus par fabrication additive

Abstract : The use of Titanium-based implantable medical devices, mainly Ti-6Al-4V alloy, significantly increased in recent decades. From a biological and chemical point of view, some elements of this alloy, such as vanadium and aluminum, are considered potentially toxic. From a mechanical point of view, Ti-6Al-4V is significantly more rigid than the cortical bone on which the prostheses/implants are attached. This difference in stiffness between the bone and the implant is at the origin of a stress deviation, called "stress-shielding", that can finally lead to loosening of the device due to bone loss. The aim of this thesis is to provide solutions for both the choice of implantable medical devices’ material and geometry, improving the transfer of charge at the interface. The dental field, where loads are important, is an appropriate environment for the implementation of these material and geometric solutions. Two types of devices are thus considered in this study: endo-osseous implants and bone plate supra-osseous implants. The positioning of conventional implants, termed endo-osseous, is evaluated with regard to the peri-implanted bone by a multiparametric numerical study, taking into account mechanical criteria. Otherwise, the supra-osseous implants are used for the rehabilitation of complete dental arches of patients with more atypical pathologies, especially when the placement of endo-osseous implants is not possible. The need to have individualized shapes to patients’ anatomy fully justifies a realization by Selective Laser Melting additive manufacturing. However, this approach requires attention in all aspects of the value chain of medical devices realization by metal additive manufacturing. In the design stage, it is not only a matter of a taking into account the mechanical strength of the implanted device but also topologically optimizing its geometry with regard to the stresses applied to the bone, to minimize stress-shielding effect. Moreover, the development of these custom-made devices has to necessarily take into account post-manufacturing finishing operations by subtractive processes. These functionalization steps still constitute a hurdle that limits the use of additive manufacturing. The problems of finishing by machining the custom-made parts are related to the transfer between the additive manufacturing machine and the machining center. The idea developed in this study is to use additive manufacturing supports as a custom-made machining fixture. To anticipate the potential instabilities during this finishing operations, a numerical model is developed and coupled with an analytical model for determining cutting forces in peripheral milling. Finally, the control of the surface quality of the devices resulting from the SLM process by sandblasting and tribofinishing is investigated, in connection with a biocompatibility study.
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  • HAL Id : tel-02558288, version 1

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Paul Didier. Solutions matériaux et géométriques pour la réalisation de dispositifs médicaux implantables sur-mesure en alliages de titane : application aux implants endo-osseux et supra-osseux obtenus par fabrication additive. Mécanique des matériaux [physics.class-ph]. Université de Lorraine, 2019. Français. ⟨NNT : 2019LORR0262⟩. ⟨tel-02558288⟩

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