The microstructure and surface chemistry of titanium dioxide on TiNbSn alloy, prepared by anodic oxidation in acetic acid electrolytes and subsequent hot water (HW) treatment, have been studied to determine the effect of HW treatment on bioactivity. HW treatment promotes TiO2 formation and photo-induced properties were observed on the anodic oxide. Cross-section energy dispersive spectroscopy analysis of the implanted anodic TiNbSn treated with HW revealed the penetration of the constituent elements of bone, Ca and P, into TiO2, which was attributed to the high bonding strength between the bone and the implanted alloy. It is proposed that the high bioactivity observed as a result of HW treatment can be ascribed to the evolution of a crystallized anodic oxide TiO2, which promotes incorporation of the primary ingredients of a bone in the oxide. (C) 2017 Elsevier B.V. All rights reserved.