Quantitative analysis of bone regeneration efficacy as shape conformity of scaffold: Evidence for importance of additive-manufacturing precision in tissue engineering

Additive manufacturing (AM) of customized scaffolds has been actively studied in tissue engineering. Most studies have focused on the functionalization of scaffolds for osteoinduction and osteoconduction for bone regeneration. However, in our previous study, we found that shape conformity between a defect and the scaffold was also a major factor with regard to enhancing bone regeneration. Thus, in this study, we performed a quantitative analysis of the shape conformity between the defect and scaffold using several novel experimental scaffolds. Employing several scaffolds with different conformities that increased linearly, the degree of bone regeneration was analyzed through new bone volume measurements and a histological analysis in conjunction with an in vivo experiment using rat calvaria. For the quantitative analysis, we compared the new bone volume reconstructed from a three-dimensional model based on CT data. New bone maturation was analyzed with respect to shape conformity through a histological analysis. Proliferation, maturation, and new bone formation were promoted by scaffold shape conformity. Thus, for bone regeneration, the AM precision and the fabrication technique are critical as the shape conformity of the scaffold to the bone defect is highly dependent on AM fabrication errors.