In the last decades, advances in bone tissue engineering mainly based on osteoinduction and on stem cell research. Only recently, new efforts by others and us focused on the micro- and nanoarchitecture needed to improve and accelerate bone regeneration. By the use of additive manufacturing, libraries of diverse microarchitectures were produced and tested to identify the ideal pore size or rod distance for osteoconduction to occur. Presently, we try to elucidate the dependency of osteoconduction on microporosity and expand our view on micro- and nanoarchitecture of bone substitutes for optimal bone augmentation.
For the production of scaffolds, we applied for titanium-based scaffolds selective laser melting and for ceramics the CeraFab 7500 from Lithoz, a lithography-based additive manufacturing machine. As in vivo test model, we used a calvarial defect and a bone augmentation model in rabbits.
The histomorphometric analysis showed that bone formation was significantly increased with pores between 0.7-1.2 mm in diameter. Best microarchitecture for osteoconduction and bone augmentation are different.   Moreover, microporosity appeared to be a strong driver of osteoconduction and influenced osteoclastic degradation for tri-calcium phosphate based scaffolds. For hydroxyapatite based scaffolds, however, microporosity appears to influence osteoconductivity to a lesser extent.
In essence, additive manufacturing enables to generate libraries of microarchitectures to search for the most osteoconductive microarchitecture for orthopaedics and the ideal microarchitecture for bone augmentation purposes. Moreover, additive manufacturing appears as a promising tool for the production of personalized bone tissue engineering scaffolds to be used in cranio-maxillofacial surgery, dentistry, and orthopaedics.