The optimal microarchitecture of 3D-printed β-TCP bone substitutes for vertical bone augmentation differs from that for osteoconduction

Synthetic bone substitutes are used for regeneration of bone defects and for vertical or horizontal bone augmentation. With the development of new manufacturing methodologies such as additive manufacturing, not only can the outer shape of a scaffold (the macroarchitecture) be personalized, but also the microarchitecture, defined as the distribution of material within the scaffold, can be designed and optimized for bone ingrowth. Our study assessed the optimal pore-based microarchitecture for osteoconduction in comparison to vertical bone augmentation. Histological analysis of the samples from an osteoconduction and a bone augmentation model showed that the best microarchitecture to achieve vertical bone augmentation contained pores of 1.7 mm diameter and differed from the optimal microarchitecture for osteoconduction, which contained pores of 1.2 mm diameter. The extent of vertical bone augmentation correlated with increasing pore diameter. Moreover, the differences between the microarchitectures were highly significant for osteoconduction, but less significant for vertical bone augmentation. Thus, our results suggest that the microarchitectures of the scaffolds in vertical bone augmentation and in bone regeneration of a defect are crucial determinants of the depth of bone ingrowth and the area of bony regeneration. However, the microarchitecture appears to be more crucial in osteoconduction.