Bioceramics and bone healing

Abstract

Calcium phosphates have long been used as synthetic bone grafts. Recent studies have shown that the modulation of composition and textural properties, such as nano-, micro- and macro-porosity, is a powerful strategy to control and synchronize material resorption and bone formation.Biomimetic calcium phosphates, which closely mimic the composition and structure of bone mineral, can be produced using low-temperature processing routes, and offer the possibility to modulate the material properties to a larger extent than conventional high temperature sintering processes.Advanced technologies open up new possibilities in the design of bioceramics for bone regeneration; 3D-printing technologies, in combination with the development of hybrid materials with enhanced mechanical properties, supported by finite element modelling tools, are expected to enable the design and fabrication of mechanically competent patient-specific bone grafts.The association of ions, drugs and cells allows leveraging of the osteogenic potential of bioceramic scaffolds in compromised clinical situations, where the intrinsic bone regeneration potential is impaired. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170056.

Keywords: Bioceramics; bone graft; bone healing; calcium phosphate.

Fig. 1

Historical overview of relevant milestones in the research and development (R&D) of calcium phosphate (CaP) biomaterials (HA, hydroxyapatite; β-TCP, beta tricalcium phosphate).

Fig. 2

Calcium phosphate cements: processing and microstructure.

Fig. 3

Scanning electron micrographs of different microstructures of calcium phosphates. Top: Biomimetic calcium-deficient hydroxyapatite (CDHA) obtained by a self-setting reaction of alpha TCP, using a coarse powder (CDHA_C) or a fine powder (CDHA_F). Bottom: Sintered calcium phosphates, beta tricalcium phosphate (β-TCP) and sintered hydroxyapatite (SHA). Scale bar: 500 nm. Adapted from Diez Escudero et al, with permission.

Fig. 4

Images of macroporous scaffolds obtained with biomimetic hydroxyapatite: a) injectable self-setting hydroxyapatite foam; b) structure obtained by 3D micro-extrusion of a self-setting hydroxyapatite ink.

Fig. 5

Bone tissue engineering requires ex vivo expansion of marrow-derived skeletal stem cells and their attachment to 3D scaffolds, such as calcium phosphate ceramic particles. This hybrid construct can be transplanted into segmental defects and will subsequently regenerate an appropriate 3D structure in vivo. Adapted from Bianco et al, with permission.