Abstract
The current gold standard bone substitute is still autologous bone, despite the fact that its harvest demands for a second operation site, causes additional pain, discomfort, potential destruction of the grafting site, and is limited in supply. Since newly developed clinical approaches like transplantation of cells are invasive and costly, and osteoinduction by bone morphogenetic proteins is expensive and is associated with mild to severe side effects, the optimization of osteoconduction appears as promising option to realize bone substitute-based bone tissue engineering. In the 90ties of the last century, the holy grail of pore size for scaffolds in bone tissue engineering was set between 0.3 and 0.5 mm. More recent, papers from others and us indicated that the optimal microarchitecture for bone tissue engineering scaffolds in terms of pore size, constrictions, rod thickness, or rod distance is still unknown. Additive manufacturing appears as an ideal tool to study those diverse microarchitecture options since it can generate scaffolds where size and location of pores and connections between pores can be tested. For the production of our test scaffolds, we applied laser sintering of titanium and lithography-based additive manufacturing of ceramics. Histomorphometry of calvarial defects in rabbits revealed that bone formation was significantly increased by scaffolds with pore diameters in the range of 0.7–1.2 mm. Scaffolds with pores of 1.5 and 1.7 mm perform significantly worse. Therefore, pore diameters in osteoconductive bone substitutes should be 1.0–1.2 mm and thus much bigger than previously suggested. In essence, osteoconductive microarchitectures of degradable bone substitutes can be realized by lithography based additive manufacturing and this methodology appears as a promising tool for the production of personalized bone tissue engineering scaffolds to be used in cranio-maxillofacial surgery, dentistry, and orthopedics.
