In Vivo Degradation Behaviour and Osteoregenerative Capacity of 3D-Printed Magnesium Phosphate and Calcium Magnesium...

Developing bone substitutes that are mechanically strong, highly biocompatible and capable of controlled degradation is crucial for successful bone regeneration. Magnesium phosphate cements (MPCs) and calcium magnesium phosphate cements (CMPCs) offer higher strength and solubility than established calcium phosphate cements (CPCs). This study aimed to evaluate the in vivo degradation, osteoregeneration and biocompatibility of 3D powder-printed Mg3d (Mg₃(PO₄)₂) and Mg275d (Ca_0.25Mg_2.75(PO₄)₂) scaffolds with alkaline post-treatment, using structurally identical TCP (Ca₃(PO₄)₂) scaffolds as the control. The scaffolds were implanted into the lateral femoral condyle of adult female Zika rabbits and analysed up to 6, 12 and 24 weeks using radiography, microCT, histology, EDX and SEM. All materials demonstrated good biocompatibility. Mg3d and Mg275d scaffolds degraded significantly faster than the TCP scaffolds, with nearly complete degradation after 12 weeks. A cell-rich reconstruction zone formed during degradation, which was subsequently replaced by new bone. The degradation rate of the scaffolds corresponded closely to bone regeneration. Notably, the Mg3d and Mg275d scaffolds supported the faster formation of mature lamellar bone compared to the TCP scaffolds. These results indicate that magnesium phosphate (MgP)-based scaffolds represent a promising alternative to conventional calcium phosphate (CP)-based bone substitutes, given their rapid and almost complete degradation and their effective support of bone regeneration.