Large-Pore 3D-Printed PLA/HA/CDHA Gyroid Scaffolds for Bone Regeneration: Effect of Unit-Cell Period in a Rabbit Calvarial Defect Model.

To evaluate late-stage bone regeneration in rabbit calvarial critical-size defects treated with 3D-printed PLA/HA/CDHA gyroid scaffolds with unit-cell periods of 0.9 or 1.2 mm, versus empty defects. In this randomized exploratory within-animal preclinical study, 12 calvarial defects were created in New Zealand White rabbits and allocated to PLA/HA/CDHA gyroid scaffolds with a 0.9-mm unit-cell period (n = 5), PLA/HA/CDHA gyroid scaffolds with a 1.2-mm unit-cell period (n = 4), or empty negative controls (n = 3). Healing was assessed after 12 weeks by micro-computed tomography and histomorphometry. At 12 weeks there was no statistically detectable difference in regenerated bone volume between groups; given the limited sample size and wide variances, this finding does not constitute evidence of equivalence. Both scaffold designs supported bone formation within the defects and showed descriptively thicker peripheral bone rims on histology than empty controls. Histomorphometric new bone area was 2.30 ± 1.16 mm2 in the 0.9-mm group and 2.43 ± 1.15 mm2 in the 1.2-mm group, compared with 1.17 ± 1.10 mm2 in controls. Vascularized surface was descriptively higher in scaffold-treated defects, with the highest mean value in the 1.2-mm group. Spatial analyses suggested more center-directed bone advancement in scaffold-treated defects, particularly in the 1.2-mm group. Spatial analyses suggested a scaffold-associated bottom-to-top (dural-side) pattern of bone advancement, while the two scaffold architectures performed similarly across bone and vascular outcomes. Although bone volume did not differ significantly between the 0.9- and 1.2-mm groups, equivalence cannot be inferred. Further longitudinal studies are needed to optimize architected composite scaffolds for craniofacial bone regeneration and dental augmentation.