Sergey V. DOROZHKIN, Self-setting calcium orthophosphate (CaPO4) formulations and their biomedical applications, Advanced Nano-Bio-Materials and Devices; 2019:3(3):321-421

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In early 1980-s, researchers discovered self-setting calcium orthophosphate (CaPO4) formulations (initially known as calcium phosphate cements), which were bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases formed pastes of variable viscosity, which set and hardened forming most commonly a bone-like non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite and rarely monetite with possible admixtures of un-reacted components. Since all these compounds were found to be biocompartible, bioresorbable and osteoconductive (therefore, in vivo they could be replaced with a newly forming bone), the self-setting CaPO4 formulations appeared to be very promising bioceramics for bone grafting purposes. Furthermore, due to their unique properties such as an easy shaping, moldability and injectability these formulations possess both an easy manipulation and a nearly perfect adaptation to the complex shapes of bone defects, followed by gradual bioresorption and new bone formation, which are additional distinctive advantages. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading them by drugs, biomolecules and even cells for tissue engineering applications. However, due to the ceramic origin, the ordinary self-setting CaPO4 formulations exhibit both a brittle nature and a low bending/tensile strength, prohibiting their use in load-bearing sites; therefore, reinforced formulations have been introduced, which might be described as CaPO4 concretes. Thus, the discovery of self-setting properties opened up a new era in the medical application of CaPO4 and many commercial trademarks have been introduced as a result. Many more formulations are still in experimental stages. In this review, an insight into the self-setting CaPO4 formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided.