This paper aims to investigate the electrochemical stability of four dental implants based on titanium alloys, rejected and recovered from patients diagnosed with peri-implantitis. The recovered implants were investigated over one week through open circuit potential (OCP) measurements, Tafel analysis, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). Patients’ X-rays and clinical data were collected. The OCP measurements showed numerous variations of the potential over time, with increases and decreases, which indicated passivation–depassivation cycles. The main corrosion parameters were obtained through Tafel analysis. Corrosion rates and polarization curves suggested a greater instability trend over time for one implant. Bode Modulus and Nyquist diagrams were obtained after EIS was performed and electrical circuits were proposed and fitted for the dental implants in order to follow the materials resistance over time. Although two implants had the highest initial recorded resistances, they showed the most decrease over time. SEM micrographs showed pitting corrosion, while the presence of the Cl element in the EDS spectra indicated the presence of chlorides associated with these processes. The analyses performed on the dental implants denoted instability, with a different behavior for each one.