Rational design of bioceramic scaffolds with tuning pore geometry by stereolithography: Microstructure evaluation and mechanical evolution

The pore geometry and structural stability of porous bioceramic are two critical variables in determining bone ingrowth. However, a significant limitation of current studies is that these two factors are often coupled due to the porous bioceramic fabrication technique, to which extent does each factor contribute to mechanical evolution. Herein we explored the effect of pore geometry on structural strength of Ca-silicate bioceramic scaffolds fabricated by stereolithography. The 3D virtual pore networks with constant porosity and average pore size were derived from the computer-assisted designing models containing strut- or curve surface-based unit cell. The cylindrical pore structure showed superior compressive and flexural resistance among the scaffolds with different pore geometries; the hexagonal cellular structure contributed on high specific compressive strength (≥50 kN∙m/Kg) and curve surface-based (skeletal-IWP, sheet-gyroid) scaffolds showed appreciable specific flexural strength (≥20 kN∙m/Kg). Furthermore, the pore structure-mechanical evolution relationships could be evaluated by immersing the scaffolds in Tris buffer for 8 weeks, and the scaffold bio-dissolution could be tuned by pore geometry design to tailor the ion release and strength decay. Basically, both Avizo software and finite element analysis demonstrate that the constant pore size models can be designed with similar total porosity but quite different stress distribution, and thus it is helpful for optimizing porous bioceramic designs with respect to their required structural and mechanical stability.