Numerical Simulation of Mechanical Behaviors of Degradable Porous Bioceramics with Cracks

Hydroxyapatite bioceramics is simulated by using finite element method （FEM）. The influences of porosity, hole shape, angle of crack and other parameters on the ceramics are analyzed. The results show that with the increase of the angle between crack and horizontal direction, the stress intensity factor KⅠ decreases gradually, but stress intensity factor KⅡ increases at first and then it decreases. The value of KⅡ reaches maximum when the angle between crack and horizontal direction is 45°. KⅠ and KⅡ rise with the increase of porosity, and they are almost the same for the circular and hexagonal holes. For elliptical holes, KⅠ and KⅡ reach maximum when the long axis of ellipse is perpendicular to the loading direction and they reach minimum when the same axis is parallel to the loading direction. Moreover, with the increase of the angle between the long axis and loading direction, KⅠ and KⅡ increase gradually.

3D printing of Mg-substituted wollastonite reinforcing diopside porous bioceramics with enhanced mechanical and biological performances

Mechanical strength and its long-term stability of bioceramic scaffolds is still a problem to treat the osteonecrosis of the femoral head.Considering the long-term stability of diopside(DIO)ceramic but poor mechanical strength,we developed the DIO-based porous bioceramic composites via dilute magnesium substituted wollastonite reinforcing and three-dimensional(3D)printing.The experimental results showed that the secondary phase(i.e.10%magnesium substituting calcium silicate;CSM10)could readily improve the sintering property of the bioceramic composites(DIO/CSM10-x,x=0-30)with increasing the CSM10 content from 0%to 30%,and the presence of the CSM10 also improved the biomimetic apatite mineralization ability in the pore struts of the scaffolds.Furthermore,the flexible strength(12.5 -30 MPa)and compressive strength(14-37 MPa)of the 3D printed porous bioceramics remarkably increased with increasing CSM10 content,and the compressive strength of DIO/CSM10-30 showed a limited decay(from 37 MPa to 29 MPa)in the Tris buffer solution for a long time stage(8 weeks).These findings suggest that the new CSM10-reinforced diopside porous constructs possess excellent mechanical properties and can potentially be used to the clinic,especially for the treatment of osteonecrosis of the femoral head work as a bioceramic rod.

A Green Biocompatible Fabrication of Highly Porous Functional Ceramics with High Strength and Controllable Pore Structures

A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 ceramics prepared via this method reached 79.6%-86.9% while these ceramics maintained high compressive strengths of 2.2-5.5 MPa. More importantly, porous A1203 ceramic with a pore size gra- dient was also readily fabricated by casting serial layers of foams that were set for different time periods. The potential applications of porous Al2O3 and HA ceramics fabricated by this green foaming method in- cluding scaffolds for oil cleaning and cell culture, respectively, were also demonstrated.

Vital role of hydroxyapatite particle shape in regulating the porosity and mechanical properties of the sintered scaffolds

The effect of particle shape on the porosity and compressive strength of porous hydroxyapatite （HA） scaffolds was investigated by sintering the mixture of rod-shaped HA （r-HA） and spherical HA （s-HA） with polyacrylamide used as the sacrificial template. It was found, for the first time, that addition of r-HA into s-HA could exponentially decrease the porosity of sintered HA scaffolds and enhance their compressive strength with the increase of r-HA content. The mechanism, according to the results from scanning electron microscopy and X-ray diffraction, lies in the restriction of s-HA to the grain formation and growth of r-HA during sintering and results in the fusion of r-HA with s-HA. These findings suggest that mixture of r-HA and s-HA might provide a new and facile way to improve the compressive strength of oorous HA scaffolds.