Biphasic, triphasic and multiphasic calcium orthophosphates.

Biphasic, triphasic and multiphasic (polyphasic) calcium orthophosphates have been sought as biomaterials for reconstruction of bone defects in maxillofacial, dental and orthopedic applications. In general, this concept is determined by advantageous balances of more stable (frequently hydroxyapatite) and more resorbable (typically tricalcium orthophosphates) phases of calcium orthophosphates, while the optimum ratios depend on the particular applications. Therefore, all currently known biphasic, triphasic and multiphasic formulations of calcium orthophosphate bioceramics are sparingly soluble in water and, thus, after being implanted they are gradually resorbed inside the body, releasing calcium and orthophosphate ions into the biological medium and, hence, seeding new bone formation. The available formulations have already demonstrated proven biocompatibility, osteoconductivity, safety and predictability in vitro, in vivo, as well as in clinical models. More recently, in vitro and in vivo studies have shown that some of them might possess osteoinductive properties. Hence, in the field of tissue engineering biphasic, triphasic and multiphasic calcium orthophosphates represent promising biomaterials to construct various scaffolds capable of carrying and/or modulating the behavior of cells. Furthermore, such scaffolds are also suitable for drug delivery applications. This review summarizes the available information on biphasic, triphasic and multiphasic calcium orthophosphates, including their biomedical applications. New formulations are also proposed.