Porous structured biphasic calcium phosphate bone grafts derived from room-temperature densified cement for bone repair

Synthetic bone substitutes are vital for bone tissue regeneration. This study assessed bone grafts made from calcium phosphate bone cement (CPC) through room-temperature densification. Sodium chloride (NaCl) was added during the hardening process of the block sample as a temporary pore-forming agent. After the NaCl leached out, it created interconnected pores. Characterizations of the synthetic grafts and commercial controls included evaluations of physicochemical properties, in vitro cytotoxicity, and in vivo bone resorption, which were compared and assessed. Granular-S and the commercial product had similar sizes, while Granular-L was larger, averaging 2.66 mm ± 0.34 mm—about 2.5 times larger than the others. The densified porous biphasic calcium phosphate graft granules contained more poorly crystalline hydroxyapatite (HA) than beta-tricalcium phosphate (β-TCP), with a ratio of 13:4, compared with the commercial product's ratio of 6:4. The densified grafts contained more poorly crystalline hydroxyapatite (HA) than beta-tricalcium phosphate (β-TCP). Biphasic grafts made from room-temperature densified bone cement have the advantage of maintaining particle integrity. These grafts feature more interconnected pores and a particle composition with a significant amount of low-crystallinity HA, which effectively promotes bioactivity. This suggests that granules composed of low-crystallinity HA and β-TCP can enhance osteoconductivity by modulating macropores, mesopores, and the biphase. All groups were non-cytotoxic, and the CPC-derived grafts did not cause inflammation after 12 weeks, unlike the commercial product, which showed inflammation due to rapid β-TCP degradation. Additionally, Granular-S exhibited greater bone resorption than the commercial product, suggesting that its combination of low-crystallinity HA and β-TCP enhances osteoconductivity and new bone formation. These developed grafts feature a higher proportion of interconnected pores, and their particle composition includes a substantial amount of low-crystallinity HA, which effectively promotes bone resorption. Consequently, they present a promising option for advanced bone tissue engineering.