Effect of sintering parameters on physicochemical and mechanical properties of 3D-printed hydroxyapatite bone scaffolds for cranio-maxillofacial bone repair

In non-load-bearing cranio-maxillofacial (CMF) defects, patient-specific bone scaffolds with controlled multiscale porosity are intended to promote vascularization and bone regeneration. Ceramic additive manufacturing offers promising solutions, though it remains limited by geometric constraints. Here, hydroxyapatite (HA) scaffolds were fabricated using the Dynamic Molding (DYMO) process, an emerging ceramic AM technique enabling highly porous and complex architectures. The effects of sintering temperature and dwell time on densification, porosity, mechanical behavior, and HA phase stability were systematically investigated. Thermal treatment was found to govern HA decomposition toward tricalcium phosphate (TCP), with high α-TCP contents yielding partially bioresorbable scaffolds. Among the conditions studied, the S2 protocol (1400 °C, 2h) offered the best compromise between densification (Archimedes density ∼ 77% theoretical density), mechanical integrity (∼ 2 MPa compressive strength, within the range reported for highly porous calcium phosphate scaffolds developed for cranio-maxillofacial repair) and controlled phase composition. These findings establish guidelines for tailoring sintering protocols to optimize DYMO-fabricated HA scaffolds for CMF bone tissue engineering application.