Estructuras de titanio con gradiente de porosidad- Fabricación por el método de partículas espaciadoras y caracterización.
Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
Congreso internacional de metalurgia y materiales.
Abstract
La gran diferencia de rigidez que hay entre los metales usados en implantes y el tejido óseo, produce
incompatibilidad mecánica (stress shielding), que lleva a la resorción del tejido óseo y al aflojamiento de las
prótesis implantadas. La introducción de poros en el titanio disminuye su módulo elástico acercándolo al
que poseen tanto los huesos corticales como trabeculares [1]. La fabricación de titanio poroso empleando el
método de partículas espaciadoras ha mostrado su practicidad y efectividad para obtener características
estructurales y mecánicas adecuadas [1, 2]. Sin embargo la anisotropía del tejido óseo, tanto en su
estructura interna como en sus propiedades mecánicas, hace necesario que el material componente de una
prótesis presente también gradiente de porosidad que imite la arquitectura del hueso y que cumpla con los
requerimientos de rigidez y resistencia mecánica a los que estará sometido [3].
En este trabajo se investigó la fabricación y caracterización de muestras de titanio con gradiente de
porosidad longitudinal usando como material espaciador carbonato ácido de amonio mezclado en distintas
proporciones con TiH2. Luego de la compactación uniaxial por capas y posterior sinterización a 1150º C, se
obtuvieron cilindros con porosidad longitudinal gradual 0/30% ,0/60%, 30/60% y 0/30/60%. Las muestras
fueron analizadas tanto en su estructura interna; tamaño, forma y distribución de poros, como en sus
propiedades mecánicas; módulo de Young y límite de fluencia.
Los resultados obtenidos indican que es posible obtener muestras sanas, con continuidad estructural entre
las distintas capas porosas, sin presencia de fisuras o segregaciones en las interfaces, con un rango de
tamaño de poro entre 300 y 350 µm, adecuado, para una correcta integración con el hueso. Los valores de
módulo de elasticidad obtenidos, fueron similares a los informados en la bibliografía para los huesos
corticales y son compatibles con la estructura anisotrópica del tejido óseo [4].
The big difference in stiffness between the metals used in implants and bone tissue, produces mechanical incompatibility (stress shielding), that leads to resorption of bone tissue and loosening of the implanted prosthesis. The introduction of pores in titanium decreases its elastic modulus moving it closer to possessing both cortical bones as trabecular [1]. The manufacture of porous titanium by the space holder method has shown its practicality and effectiveness to obtain adequate structural and mechanical characteristics [1, 2]. However anisotropy of bone tissue, both in its internal structure and its mechanical properties, makes it necessary the material component of a prosthesis to present also porosity gradient that mimics bone architecture and meets the requirements of stiffness and strength that will be subjected [3]. This paper describes the fabrication and characterization of titanium samples with longitudinal porosity gradient, using as space holder material ammonium hydrogen carbonate in different proportions mixed with titanium hydride. After layered uniaxial compactation and subsequent sintering at 1150 ° C, cylinders with gradual longitudinal porosity 0/30%, 0/60% 30/60% and 0/30/60% were obtained. Internal structure; size, shape and pore distribution, and mechanical properties; Young's modulus and yield stress were analyzed in samples obtained. The results indicate that by the method studied, it is possible to obtain healthy samples, structural continuity between the different porous layers, without the presence of cracks or segregations in the interfaces, with a range of pore size between 300 and 350 µm, suitable, for proper integration with the bone. The values of modulus of elasticity in compression were similar to those reported in the literature for cortical bones and are compatible with the bone tissue anisotropic structure [4].
The big difference in stiffness between the metals used in implants and bone tissue, produces mechanical incompatibility (stress shielding), that leads to resorption of bone tissue and loosening of the implanted prosthesis. The introduction of pores in titanium decreases its elastic modulus moving it closer to possessing both cortical bones as trabecular [1]. The manufacture of porous titanium by the space holder method has shown its practicality and effectiveness to obtain adequate structural and mechanical characteristics [1, 2]. However anisotropy of bone tissue, both in its internal structure and its mechanical properties, makes it necessary the material component of a prosthesis to present also porosity gradient that mimics bone architecture and meets the requirements of stiffness and strength that will be subjected [3]. This paper describes the fabrication and characterization of titanium samples with longitudinal porosity gradient, using as space holder material ammonium hydrogen carbonate in different proportions mixed with titanium hydride. After layered uniaxial compactation and subsequent sintering at 1150 ° C, cylinders with gradual longitudinal porosity 0/30%, 0/60% 30/60% and 0/30/60% were obtained. Internal structure; size, shape and pore distribution, and mechanical properties; Young's modulus and yield stress were analyzed in samples obtained. The results indicate that by the method studied, it is possible to obtain healthy samples, structural continuity between the different porous layers, without the presence of cracks or segregations in the interfaces, with a range of pore size between 300 and 350 µm, suitable, for proper integration with the bone. The values of modulus of elasticity in compression were similar to those reported in the literature for cortical bones and are compatible with the bone tissue anisotropic structure [4].
Description
Keywords
Titanio, Gradientes de porosidad, Carbonato ácido
Citation
16º SAM/CONAMET
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Review
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