Tough and Osteocompatible Calcium Phosphate Cements Reinforced with Poly(vinyl alcohol) Fibers

Injectable, self-setting calcium phosphate cements (CPCs) are favorable bone substitutes due to their osteocompatibility. However, due to their brittleness and low toughness, their clinical application is limited to non-load-bearing sites. The incorporation of poly(vinyl alcohol) (PVA) fibers into cementitious materials is a successful strategy in civil engineering for improving the mechanical performance of cements. However, PVA fibers in particular have not yet been applied to reinforce CPCs. Therefore, the aim of this study is to investigate the effect of PVA fibers on the mechanical properties of CPCs. Second, the in vitro cytocompatibility of these fibers is studied using cell culture tests. Finally, the in vivo osteocompatibility of PVA fiber-reinforced CPCs is studied after a 6 and 12 week implantation period in the femoral condyle of rabbits. Results reveal that the incorporation of PVA fibers into CPCs is a highly effective strategy to strengthen and toughen CPCs, since the flexural strength and toughness of CPCs increased by more than 3-fold and 435-fold, respectively, upon reinforcement with PVA fibers. In vitro cytocompatibility tests indicate that PVA fibers are cytocompatible, which is further confirmed by the in vivo results that show that PVA fibers do not compromise the excellent osteocompatibility of CPCs.