Impact of 3D-Printed Tricalcium Phosphate Scaffold Polymorphism and Post-Processing Variations on Bone Regenerative Outcomes.

Tricalcium phosphate (TCP) bioceramics, available as α- and β-polymorphs, are frequently employed in the production of three-dimensionally (3D) printed bone scaffolds. Although hydrothermal immersion processing (HP) and sintering (S) are commonly adopted as post-printing techniques for bioceramics, a comprehensive comparative analysis of their effects on the osteogenic performance of α- and β-polymorphs in vivo remains inadequately investigated. In this study, α-TCP and β-TCP scaffolds were fabricated via direct ink writing and subjected to hydrothermal immersion processing (α-TCP/HP) and sintering (β-TCP/S) prior to implantation in n = 12 skeletally mature sheep (n = 1 scaffold per group per animal), and the outcome variables were evaluated at 3 and 12 weeks postoperatively (n = 6 sheep per time point). The quantitative results showed no significant differences in bone deposition or scaffold resorption at 3 weeks postoperatively (p = 0.618 and p = 0.898, respectively). However, at 12 weeks, there was a significant increase in osteogenesis and scaffold resorption in the β-TCP/S cohort relative to the α-TCP/HP counterparts (p < 0.001 and p = 0.004, respectively). β-TCP scaffolds subjected to post-print sintering exhibited superior osteoconductive and resorptive profiles compared to hydrothermal immersion-processed α-TCP scaffolds over the 12-week healing period.