Machining matters: unraveling the electrochemical behavior of Ti6AL4V dental implants in simulated biological environments

Abstract

This study investigates the impact of machining processes on the electrochemical behavior of Ti6AL4V alloy dental implants immersed in a simulated biological solution (SBF). Four distinct implant samples were crafted under varying machining conditions, and their electrochemical responses were assessed through potentiodynamic polarization (PDP) curves and electrochemical impedance spectroscopy (EIS) at room temperature. The exploration extends to the calculation of corrosion kinetics parameters via Tafel extrapolation and impedance analyses. Notably, the S750-Q0.01 sample exhibited the lowest corrosion current density (I_corr = 1.3166 µA/cm²) and the highest polarization resistance (Rp = 616 Ohm cm²), indicating superior corrosion resistance. In contrast, the S750-Q0.12 sample showed the highest dislocation density (1.037), signifying notable microstructural alterations. Electrochemical impedance results further revealed that samples machined at higher spindle speeds and lower cutting depths, such as S1000-Q0.01, exhibited higher resistance to corrosion with Rp values reaching 4396 Ohm cm². Bioactivity analysis through Ca/P ratios demonstrated that the S1000-Q0.01 sample formed the most bioactive apatite layer with a Ca/P ratio close to hydroxyapatite standards. Phase analysis was carried out using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The outcomes revealed distinct corrosion behaviors in the SBF solution for machined implants under different conditions, signifying the significant influence of machining variations on microstructural changes and implant performance.