The effect of pores and connections geometries on bone ingrowth into titanium scaffolds: an assessment based on 3D microCT images

In order to support bone tissue regeneration, porous biomaterial implants (scaffolds) must offer chemical and mechanical properties, besides favorable fluid transport. Titanium implants provide these requirements, and depending on their microstructural parameters, the osteointegration process can be stimulated. The pore structure of scaffolds plays an essential role in this process, guiding fluid transport for neo-bone regeneration. The objective of this work was to analyze geometric and morphologic parameters of the porous microstructure of implants and analyze their influences in the bone regeneration process, and then discuss which parameters are the most fundamental. Bone ingrowths into two different sorts of porous titanium implants were analyzed after 7, 14, 21, 28, and 35 incubation days in experimental animal models. Measurements were accomplished with x-ray microtomography image analysis from rabbit tibiae, applying a pore-network technique. Taking into account the most favorable pore sizes for neo-bone regeneration, a novel approach was employed to assess the influence of the pore structure on this process: the analyses were carried out considering minimum pore and connection sizes. With this technique, pores and connections were analyzed separately and the influence of connectivity was deeply evaluated. This investigation showed a considerable influence of the size of connections on the permeability parameter and consequently on the neo-bone regeneration. The results indicate that the processing of porous scaffolds must be focused on deliver pore connections that stimulate the transport of fluids throughout the implant to be applied as a bone replacer.

Development, Characterization and In Vitro Biological Properties of Scaffolds Fabricated From Calcium Phosphate Nanoparticles

Ceramic materials mimic the mineral composition of native bone and feature osteoconductive properties; they are therefore used to regenerate bone tissue. Much research focuses on increasing the porosity and pore interconnectivity of ceramic scaffolds to increase osteoconductivity, cell migration and cell-cell interaction. We aimed to fabricate biocompatible 3D-scaffolds featuring macro- and microporous calcium phosphates with high pore interconnection. Nanoparticles of hydroxyapatite (HA) and calcium deficient hydroxyapatite (CDHA) were synthesized by wet chemical precipitation. Scaffolds were produced from them by the replication polymeric foam technique. Solid content and sintering temperature were varied. Nanoparticles and scaffolds were characterized regarding morphology, chemical and mineral composition, porosity and mechanical properties. Biocompatibility, cell attachment and distribution were evaluated in vitro with human adipose mesenchymal stem cells. Scaffolds with total porosity of 71%-87%, pores in the range of 280-550 µm and connectivity density up to 43 mm-3 were obtained. Smaller pore sizes were obtained at higher sintering temperature. High solid content resulted in a decrease of total porosity but increased interconnectivity. Scaffolds 50HA/50β-TCP featured superior interconnectivity and mechanical properties. They were bioactive and biocompatible. High HA solid content (40 wt.%) in the HA pure scaffolds was negative for cell viability and proliferation, while in the 50HA/50β-TCP composite scaffolds it resulted more biocompatible.