Unpredictable Electrochemical Processes in Ti Dental Implants: The Role of Ti Ions and Inflammatory Products.

Peri-implantitis is a substantially prevailing condition. A potential risk factor for peri-implantitis is Ti implant corrosion. During inflammation, substantial quantities of reactive oxygen species (ROS) secretion and local acidification occur. Little is known about the interaction between the inflammatory and corrosion products on Ti surface corrosion. Therefore, the objective of the current study was to evaluate the synergistic effect of hydrogen peroxide (H 2 O 2 ), lactic acid, and Ti ions on Ti corrosion. Twenty-seven commercially pure Ti samples were polished (Ra ≈ 45 nm) and divided into 9 groups as a function of electrolyte: (1) artificial saliva (AS) as control (C), (2) AS + Ti ions 20 ppm (Ti), (3) AS + lactic acid (pH = 5.5) (L), (4) AS + lactic acid + Ti ions 20 ppm (TiL), (5) AS + H 2 O 2 0.5 mM (HP 0.5 ), (6) AS + H 2 O 2 1.0 mM (HP 1.0 ), (7) AS + H 2 O 2 0.5 mM + Ti ions 20 ppm (HP 0.5 Ti), (8) AS + H 2 O 2 0.5 mM + lactic acid (HP 0.5 L), and (9) AS + H 2 O 2 0.5 mM + Ti ions 20 ppm + lactic acid (HP 0.5 TiL). Electrochemical tests were performed following ASMT guidelines. Based on Tafel's method, current density ( i corr ) and corresponding potential ( E corr ) were acquired from potentiodynamic curves. Using electrochemical intensity spectroscopy (EIS), Nyquist and Bode plots were derived. Using a modified Randles circuit, charge transfer resistance ( R ct ) and capacitance ( C dl ) were estimated. Based on open-circuit potential data, groups C and Ti had the lowest potentials (around -0.3 and -0.4 V vs SCE, respectively), indicating a lower passivation tendency compared to the other groups. From potentiodynamic curves, groups HP 0.5 and HP 1.0 increased i corr the most. From EIS data, groups HP 0.5 and HP 1.0 demonstrated the lowest impedance and phase angle on the Bode plot, indicating the highest corrosion kinetics. Based on EIS modeling, the combination of Ti ions, lactic acid, and H 2 O 2 (group HP 0.5 TiL) significantly decreased R ct ( p < 0.05). In conclusion, the concurrent presence of Ti ions, lactic acid, and H 2 O 2 in the vicinity of the Ti surface increased the corrosion kinetics. High corrosion may produce more Ti products in the peri-implant tissues, which may increase the potential risk of peri-implantitis.