Topography-dependent Biological Activities Of Titanium

After nearly half a century of development under the guidance of osseointegration theory, dental implant therapy is now widely accepted and revolutionizes dental rehabilitation. Surface topography has been identified as a crucial property that affects osseointegration, thus makes topographical modification the most frequently adopted route in titanium (Ti) implant research. The majority of the commercially available Ti implant surfaces are modified by architecting the surface with microscale features, which has been evidenced to enhance osteogenic differentiation and optimize stress distribution. However, Ti-based implant is still encountered with certain clinical challenges, deficient osseointegration and implant associated infection. Moreover, biological aging of Ti implant also brings great uncertainty to clinical results.In the present study, topography-dependent biological activity of Ti was studied from the aspects of antibacteria property, biological aging, macrophage responsiveness and osseointegraiton.Based on the nano-micro-hierarchical structure model on Ti, it was found that the the nano-micro-hierarchical structure had topography-dependent antibacterial capacity via inhibiting bacterial adhesion of several species in the early stage. Aging study demonstrates that, compared with the surface with microscale structure, the nano-micro-hierarchical Ti surface has greater anti-aging ability manifested as being more capable to retain hydrophilicity and bioactivity during aging. Furthermore, the present study revealed that the biological aging of the Ti implant was attributed to two decisive factors:the progressively thickened amorphous TiO2layer by autoxidation and the unavoidable accumulation of hydrocarbons on Ti implant surface from the enviroment. Moreover, this study also found that both microstured Ti surface and the nano-hierarchical structured surface regulated the polarization of macrophage. The nano-micro-hierarchical structured Ti surface was associated with less proinflammatory phenotype in vitro and more bone formation in vivo compared to the microstructured Ti surface.This study opened a door to develop a new generation of antibacterial and osteogenic Ti implants. The mechanism of the biological aging discovered in the present study would provide theoretical guidance for anti-aging research on Ti implants. Moreover, surface structure induced macrophage polarization provides a framework for predicting the performance of biomaterials after implantation.