Biomimetic Response of Zr-2.5Nb Alloy to Artificial Saliva with Variable pH: Corrosion Behavior and Surface Adaptation

The long-term performance of metallic biomaterials in the oral environment is strongly influenced by their interaction with saliva and its variable chemical conditions. In this study, the biomimetic behavior of a Zr-2.5Nb alloy was investigated during immersion in artificial saliva with acidic, neutral, and alkaline pH for a period of 28 days, aiming to simulate diverse physiological and pathological oral conditions. The evolution of saliva pH was continuously monitored throughout the immersion period to assess the dynamic material-environment interactions. Surface morphology, elemental composition, and chemical structure were analyzed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) and Fourier-transform infrared spectroscopy (FTIR), while corrosion resistance was evaluated through electrochemical measurements. The results revealed distinct pH-dependent surface responses, with acidic saliva promoting localized surface modifications and increased corrosion susceptibility, whereas neutral conditions favored the formation of stable and protective passive layers, and alkaline environments promoted the development of chemically complex surface layers that exhibited initial stabilization but underwent progressive degradation during long-term exposure. Overall, the Zr-2.5Nb alloy demonstrated a high degree of corrosion resistance and chemical stability, particularly under neutral and alkaline conditions, supporting its suitability for dental and oral biomedical applications. These findings provide a biomimetic perspective on pH-driven surface adaptation and long-term corrosion behavior, highlighting how dynamic material-environment interactions govern the performance of zirconium-based biomaterials in complex oral environments.