Comparative Surface and Early Biological Responses of α ‐, α + β ‐, and β ‐Type Titanium Alloys

This study investigates the surface and early biological responses of three titanium (Ti) alloys with different phase constitutions and alloy chemistries. Commercially, pure Ti (CP‐Ti), Ti‐6Al‐4V, and Ti‐45Nb were selected as representative α ‐, α + β ‐, and β ‐type alloy systems, respectively. Polished and metallographically etched specimens were compared to examine how their coupled phase constitution and alloy chemistry were associated with changes in surface properties and biological responses. Wettability and surface energy were evaluated by contact angle analysis, and also calcium‐phosphate/apatite‐like formation was assessed after 7 and 14 days of immersion in simulated body fluid (SBF). Early biocompatibility was evaluated using MG‐63 osteoblast‐like cells. Etching decreased hydrophilicity in CP‐Ti and Ti‐6Al‐4V but increased it in Ti‐45Nb. Calcium‐phosphate/apatite‐like deposits were not detected on CP‐Ti, were limited and delayed on Ti‐6Al‐4V, and were extensively observed on Ti‐45Nb. Ti‐45Nb also exhibited the highest MG‐63 cell viability under both surface conditions. The contrasting responses suggest that early surface and biological behavior varied among the investigated alloy systems through a combined influence of crystallographic phase constitution, alloy chemistry, and etching‐induced surface changes. Among the investigated materials, Ti‐45Nb exhibited the most favorable overall surface and early biological response.