Background
Given their highly adjustable and predictable properties, three-dimensional(3D) printed geometrically ordered porous biomaterials offer unique opportunities as orthopedic implants. The performance of such biomaterials is, however, as much a result of the surface properties of the struts as it is of the 3D porous structure. In our previous study, we have investigated the in vitro performances of selective laser melted (SLM) Ti-6Al-4V scaffolds which are surface modified by the bioactive glass (BG) and mesoporous bioactive glass (MBG), respectively. The results demonstrated that such modification enhanced the attachment, proliferation, and differentiation of human bone marrow stromal cells (hBMSC). Here, we take the next step by assessing the therapeutic potential of 3D printed Ti-6Al-4V scaffolds with BG and MBG surface modifications for bone regeneration in a rabbit bone defect model.

Methods
3D printed Ti-6Al-4V scaffolds with BG and MBG surface modifications were implanted into the femoral condyle of the rabbits, the Ti-6Al-4V scaffolds without surface modification were used as the control. At week 3, 6, and 9 after the implantation, micro-computed tomography (micro-CT) imaging, fluorescence double-labeling to determine the mineral apposition rate (MAR), and histological analysis of non-decalcified sections were performed.

Results
We found significantly higher volumes of regenerated bone, significantly higher values of the relevant bone morphometric parameters, clear signs of bone matrix apposition and maturation, and the evidence of progressed angiogenesis and blood vessel formation in the groups where the bioactive glass was added as a coating, particularly the MGB group.

Conclusions
The MBG coating resulted in enhanced osteoconduction and vascularization in bone defect healing, which was attributed to the release of silicon and calcium ions and the presence of a nano-mesoporous structure on the surface of the MBG specimens.@en