Toward Strong and Tough Glass and Ceramic Scaffolds for Bone Repair

Abstract

The need for implants to repair large bone defects is driving the development of porous synthetic scaffolds with the requisite mechanical strength and toughness in vivo. Recent developments in the use of design principles and novel fabrication technologies are paving the way to create synthetic scaffolds with promising potential for reconstituting bone in load-bearing sites. This article reviews the state of the art in the design and fabrication of bioactive glass and ceramic scaffolds that have improved mechanical properties for structural bone repair. Scaffolds with anisotropic and periodic structures can be prepared with compressive strengths comparable to human cortical bone (100–150 MPa), while scaffolds with an isotropic structure typically have strengths in the range of trabecular bone (2–12 MPa). However, the mechanical response of bioactive glass and ceramic scaffolds in multiple loading modes such as flexure and torsion — as well as their mechanical reliability, fracture toughness, and fatigue resistance — has received little attention. Inspired by the designs of natural materials such as cortical bone and nacre, glass-ceramic and inorganic/polymer composite scaffolds created with extrinsic toughening mechanisms are showing potential for both high strength and mechanical reliability. Future research should include improved designs that provide strong scaffolds with microstructures conducive to bone ingrowth, and evaluation of these scaffolds in large animal models for eventual translation into clinical applications.

Nanoporosity improved water absorption, in vitro degradability, mineralization, osteoblast responses and drug release of poly(butylene succinate)-based composite scaffolds containing nanoporous magnesium silicate compared with magnesium silicate

“…28,29 In this study, the sphericalshaped NMS particles with the size of ~200 nm and irregular MS particles with the size of ~1 μm (some MS particles aggregated together to form more bigger particles with size of several micrometers) were fabricated, and the NMS and MS as bioactive materials were incorporated into PBSu matrix to form bioactive composite scaffolds by solvent castingparticulate leaching method. The results showed that both the NMS and MS particles dispersed into polymer phases, and no obvious NMS particles were found on the surface of macroporous NMPC scaffold, while some obvious particles with the size of ~1 μm were found on the surface of MPC scaffold.…”

Fatigue prediction in fibrin poly-ε-caprolactone macroporous scaffolds

“…Fu et al (Fu et al, 2013) reported that compressive strength of bioactive scaffolds decreases with the porosity increase present in the samples. Moreover, fatigue performance of bovine bone during cyclic loading results in a reduction of the elastic modulus and accumulation of residual strain leading to a progressive reduction of fatigue life with increasing stress levels (Ganguly et al, 2004).…”

Finite Element Modeling of the Flexural Mechanical Response of Polymer-Coated Bioactive Glass Scaffolds Composed of Thermally-Bonded Unidirectional Fibers

“…Bioactive glasses can be formed using conventional and additive manufacturing methods into porous three-dimensional (3D) scaffolds with the requisite architecture to support tissue infiltration and angiogenesis. On the other hand, porous bioactive glass scaffolds are brittle and often have a low strength which limit their mechanical reliability in vivo [5,6].…”

“…As shown for porous bioceramic scaffolds [7][8][9][10], coating the external and internal surface of porous bioactive glass scaffolds with a biodegradable polymer such as polylactic acid (PLA) or polycaprolactone (PCL) can have a strong effect on their mechanical response [6,[11][12][13]. The strength and, in particular, the work of fracture of these polymercoated bioactive glass scaffolds have shown considerable increases over the uncoated scaffolds due to crack bridging and crack healing mechanisms enabled by the polymer coating [6,11]. The work of fracture, defined as the total energy consumed in creating unit area of fracture surface during complete fracture, is taken as a measure of toughness when comparing materials within a given group.…”