Biological evaluation of ultra-fine titanium with improved mechanical strength for dental implant engineering

Titanium, the gold standard for dental implant materials, is distinguished by its exceptional biocompatibility; however, from a long-term perspective, titanium still lacks sufficient loading strength. Commercially pure titanium with grain size 30 μm was processed by equal channel angular pressing, and two novel mechanically improved types of titanium material with grain size 4.6 and ≤1 µm were obtained. The surfaces of these ultra-fine grained titanium samples were further mechanically treated by grinding and polishing, and their surfaces were characterized by atomic force microscopy and contact angle measurement. Osteoblast-like cells and human mesenchymal stem cells were used to evaluate the cytocompatibility of these titanium samples. The cell metabolic activity, cell number, cell area, morphology, and cell adhesion quality during the early stage (2 h) and prolonged cultivation (48 h) were determined. Both cell types displayed increased initial attachment to all tested titanium materials in comparison to reference tissue culture plastic. Importantly, results revealed that the novel titanium materials with improved strength were equivalent to the original commercially pure titanium, thus confirming their suitability for osteoblast and mesenchymal stem cell growth and proliferation. The present study proved the cytocompatibility of the novel forms of titanium with superior mechanical properties and revealed their potential for manufacturing of long-term dental implants.