Self-Setting Calcium Orthophosphate (CaPO4) Formulations

Abstract

In the early 1980s, researchers discovered self-setting calcium orthophosphate (CaPO4) cements, which are bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases form pastes of variable viscosity, which set and harden forming most commonly a non-stoichiometric calcium-deficient hydroxyapatite (CDHA) or brushite and rarely monetite with possible admixtures of unreacted compounds. As CDHA, brushite and monetite appear to be biocompatible, bioresorbable, and osteoconductive (therefore, in vivo they can be replaced with a newly forming bone), self-setting CaPO4 formulations come out to be very promising bioceramics for bone grafting. Furthermore, due to their moldability, such formulations possess 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. Unfortunately, the mechanical properties of the ordinary self-setting CaPO4 formulations are poor; therefore, reinforced ones have been introduced. The latter might be described as CaPO4 concretes. In addition, porous formulations have been developed. 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. Currently such formulations are widely used as synthetic bone grafts, with several advantages, such as moldability, pourability, and injectability. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading by drugs, biomolecules, and even cells for tissue engineering purposes. In this chapter, an insight into the self-setting CaPO4 formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided.