Preparation and performance evaluation of monetite-type bone paste containing gelatinized starch

Abstract

Bone fillers are used for bone defects caused by injury or disease. One type of such a bone replacement material is a bone cement that hardens by mixing calcium phosphates powder in a physiological environment. We have prepared gelatinized starch-containing bone pastes that harden by forming hydroxyapatite [HAp; Ca₁₀(PO₄)₆(OH)₂] while providing excellent handling property by mixing the powder and a gelatinized wheat starch. In this study, a starch-containing monetite-type bone paste was prepared by kneading bioabsorbable and biocompatible anhydrous calcium hydrogen phosphate (DCPA; CaHPO₄) powder with the gelatinized starch, and its properties were compared with those of the starch-containing HAp-type paste. The operability of the monetite-type paste samples was poor than that of HAp-type paste. In terms of crystalline phase, the monetite-type paste showed slightly different peak patterns attributed to DCPA before and after hardening, suggesting dissolution and reprecipitation of DCPA during soaking to set, while the HAp-type paste formed mainly HAp with trace amount of residual tetracalcium phosphate. Initial setting time of the monetite-type paste was longer than that of HAp-type one. Compressive strength exceeded 40 MPa for both of the sample types. In vitro bioabsorbability of the monetite-type paste was higher than that of HAp-type one. Furthermore, the hydrophilicity of the monetite-type paste was higher than that of HAp-type one. This suggests that starch-containing monetite-type bone pastes are expected to be partially replaced by autogenous bone as the hardened material is resorbed in vivo.