Investigating the integrity of titanium-oxide nanolayers of Ti6Al4V under chemo-mechanical stress

Titanium-based biomaterials show a high success rate and excellent biocompatibility due to their properties, that can be partly attributed to the titanium's ability to form a protective oxide layer. As such they are widely used, mostly Ti6Al4V, to manufacture dental implants and prosthetic devices. Unfortunately, implant failures can arise during implant use and are mainly due to peri-implant diseases involving bacterial infection and inflammatory stimuli. This study performs a systematic nano-structural evaluation of the contribution of inflammatory-simulating conditions (H₂O₂ and lactic acid), aside with room air and saline solution, combined with repeated mechanical loading, to the damage generated on the titanium surface and to the titanium oxide integrity. By using an array of high-resolution characterization techniques, such as ToF-SIMS and TEM, the synergy between mechanical loads and chemical reactions was unraveled. In the more aggressive environments (e.g. lactic acid and H₂O₂), a clear increase in the titanium oxide's thickness was observed compared to inert environments, such as air and saline. The effect of the mediums was more pronounced in the presence of loads. The TEM analysis observations revealed the porous and permeable nature of the oxide layer, affecting its neutrality and hence its biocompatibility.