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International audience; Autologous bone graft is considered as the gold standard in bone reconstructive surgery. However, the quantity of bone available is limited and the harvesting procedure requires a second surgical site resulting in severe complications. Due to these limits, scientists and clinicians have considered alternatives to autologous bone graft. Calcium phosphates (CaPs) biomaterials including biphasic calcium phosphate (BCP) ceramics have proven efficacy in numerous clinical indications. Their specific physico-chemical properties (HA/TCP ratio, dual porosity and subsequent interconnected architecture) control (regulate/condition) the progressive resorption and the bone substitution process. By describing the most significant biological responses reported in the last 30 years, we review the main events that made their clinical success. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine. Statement of Significance Nowadays, BCPs are definitely considered as the gold standard of bone substitutes in bone reconstructive surgery. Among the numerous clinical studies in literature demonstrating the performance of BCP, Passuti et al. and Randsford et al. studies largely contributed to the emergence of the BCPs. It could be interesting to come back to the main events that made their success and could explain their large adhesion from scientists to clinicians. This paper aims to review the most significant biological responses reported in the last 30 years, of these BCP-based materials. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine.

International audience; The influence of cellulose ether additives (CEAs) on the performance of final calcium phosphate cement (CPC) products is thoroughly investigated. Four CEAs were added into the liquid phase of apatitic CPCs based on the hydrolysis of α-tricalcium phosphate, to investigate the influence of both molecular weight and degree of substitution on the CPCs' properties, including handling (e.g. injectability, cohesion, washout resistance and setting time), microstructure (e.g. porosity and micromorphology) and mechanical properties (e.g. fracture toughness and compressive strength). The results showed that even a small amount of CEAs modified most of these CPCs' features, depending on the structural parameters of the CEAs. The CEAs dramatically improved the injectability, cohesion and washout resistance of the pastes, prolonged the final setting time and increased the porosity of CPCs. Moreover, the CEAs had an evident toughening effect on CPCs, and this effect become more significant with increasing molecular weight and mass fraction of CEAs, inducing a significant tolerance to damage. Overall, the molecular weight of CEAs played a major role compared to their degree of substitution in CPCs' performances.

There is a growing interest in bone tissue engineering for bone repair after traumatic, surgical or pathological injury, such as osteolytic tumor or osteoporosis. In this regard, calcium phosphate (Cap) bone substitutes have been used extensively as bone-targeting drug-delivery systems. This localized approach improves the osteogenic potential of bone substitutes by delivering bone growth factors, thus extending their biofunctionality to any pathological context, including infection, irradiation, tumor and osteoporosis. This review briefly describes the physical and chemical processes implicated in the preparation of drug-delivering CaPs. It also describes the impact of these processes on the intrinsic properties of CaPs, especially in terms of the drug-release profile. In addition, this review focuses on the potential influence of drugs on the resorption rate of CaPs. Interestingly, by modulating the resorption parameters of CaP biomaterials, it should be possible to control the release of bone-stimulating ions, such as inorganic phosphate, in the vicinity of bone cells. Finally, recent in vitro and in vivo evaluations are extensively reported. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.