3D Characterization of Human Nano-osseointegration by On-Axis Electron Tomography without the Missing Wedge.

Three-dimensional (3D) visualization of bone-implant interfaces via electron tomography (ET) has contributed to the novel perspective of nano-osseointegration and offers evidential support for nanoscaled biomaterial surface modification. Conventional single-axis ET provides a relatively large field of view of the human bone to titanium implant interface showing bone structure arrangement near the interface. However, the "missing wedge" associated with conventional single-axis ET leads to artifacts and elongation in the reconstruction, limiting the resolution and fidelity of reconstructions, as well as the ability to extract quantitative information from nanostructured interfaces. On-axis ET, performed by 180° rotation of a needle-shaped sample, is a promising method to solve this problem. In this work, we present the first application of on-axis ET for investigation of human bone and laser-modified titanium implant interfaces without the missing wedge. This work demonstrates a near artifact-free 3D visualization of the nanotopographies of the implant surface oxide layer and bone growth into these features. Complementary electron energy-loss spectroscopy (EELS) mapping was used to illustrate the gradual intermixing of carbon and calcium (characteristic elements of bone) with the nanoscaled oxide layer of the implant surface. Ultimately, this approach serves as direct evidence of nano-osseointegration and as a potential platform to evaluate differently structured implant surfaces.