High-Resolution Visualization of the Osteocyte Lacuno-Canalicular Network Juxtaposed to the Surface of Nanotextured Titanium Implants in Human

Osseointegration is controlled by a number of cellular mechanisms. Although factors governing bone formation are well-understood, the maintenance of bone at the bone-implant interface is less clear. Of some interest is the role of osteocytes, which via mechanotransduction are believed to be responsible for mechanical loading-based remodelling events in bone. Using a resin cast etching technique, we investigated the osteocyte lacuno-canalicular network adjacent to nanostructured titanium human dental implants after four years in clinical function. Correlative electron microscopy showed nanoscale osteocyte processes extending directly onto the implant surface. Calcium signal mapping via electron energy loss spectroscopy (EELS) showed apatite ingrowth into the nanotextured surface, while the apatite platelet c-axis was oriented approximately parallel to the collagen fibril direction. Furthermore, Z-contrast electron tomography demonstrated that natural bone-osteocyte and engineered bone-implant interfaces are similar in ultrastructural morphology. The present ultrastructural observation of multiple connections between osteocyte canaliculi and the nanotextured surface oxide suggests that osteocytes contribute toward the maintenance of osseointegration in long-term clinical function.