Comparative in vivo study of 3D-printed composite bioceramic scaffolds fabricated by distinct pre-processing methods

This study aimed to evaluate the in vivo osteoinductive potential and biocompatibility of three-dimensional (3D) printed bone substitutes composed of polylactic acid (PLA) and PLA-based bioceramic composites of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), fabricated using distinct pre-processing methods. Pure PLA, thermally blended PLA/HA/β-TCP, and tetrahydrofuran (THF) solvent-cast PLA/HA/β-TCP (7:3w/w) were first processed into 1.75 mm filaments and subsequently fabricated into scaffolds using fused deposition modeling (FDM). These scaffolds were implanted subcutaneously in 8-week-old Sprague–Dawley (SD) rats. Histological and immunohistochemical analyses were performed at 2 and 4 weeks, as per ISO 10993-6, to evaluate inflammation, fibrous capsule formation, and osteogenic potential. Semi-quantitative scoring revealed that T-MIX (tetrahydrofuran solvent-cast composite) had the lowest inflammatory scores at both 2 and 4 weeks, which were significantly lower than those of H-MIX (heat-blended composite) ( P < 0.05). At 2 weeks, BSP (bone sialoprotein) expression in both H-MIX and T-MIX was significantly higher than in PLA ( P < 0.05 and P < 0.001, respectively), with T-MIX also exceeding H-MIX ( P < 0.05). Overall, T-MIX demonstrated superior performance in reducing inflammation and promoting osteogenesis. The solvent-cast T-MIX scaffold demonstrated significantly reduced inflammatory responses and enhanced osteogenic marker expression compared to both pure PLA and heat-blended composites, positioning it as a promising and standardized candidate for 3D-printed, patient-specific bone grafts in dental and craniofacial applications.