New insights on regulating degradation and osteogenesis of magnesium phosphate cement via α-TCP and gypsum-based fiber incorporation

The development of bone repair materials that balance handleability, mechanical strength, degradation rate, and osteogenic efficiency remain a major challenge in orthopedics. To address the limitations of pure magnesium phosphate cement (MPC), such as its overly rapid setting, high exothermicity, and insufficient osteogenicity, this study innovatively introduced α-tricalcium phosphate (α-TCP) and gypsum fibers into MPC matrix to fabricate a novel composite cement. Systematic characterization demonstrated that α-TCP incorporation significantly prolonged the injectable and setting times, reduced the hydration heat, and yielded appreciable compressive strength (∼42 MPa) alongside a denser microstructure in the MPC/TCP-20 group. In vitro degradation tests confirmed its sustained multi-ionic release and excellent biomineralization capacity. Crucially, by engineering the MPC/TCP-EX group with surface-exposed gypsum fibers, we successfully modulated the degradation pathway and osteogenesis pattern. The preferential degradation of gypsum fibers created internal microchannels, guiding concurrent internal and external bone ingrowth, which resulted in the most significant bone regeneration (BV/TV of 41.8% at 16 weeks) and limited material residual in a rabbit femoral defect model. Totally, these findings provide a new strategy for developing high-performance bone cements that may dynamically match the bone regeneration process through a synergistic “composition-structure” design. • A core-shell MPC/α-TCP cement with surface-exposed gypsum fibers was fabricated. • α-TCP tunes setting time, strength, and degradation of the cement. • A novel “degradation-guided osteogenesis” mechanism is demonstrated. • Exposed fibers create internal channels for bidirectional bone ingrowth. • Synergy of “composition-structure” design enhances bone regeneration.