Pepsin-driven corrosion of orthodontic titanium alloys in candidiasis-simulated saliva: electrochemical and statistical insights

Ti-6Al-4 V titanium alloy is widely utilized in orthodontic applications due to its favorable biocompatibility and mechanical properties. However, its long-term performance can be adversely affected by the dynamic and hostile oral environment, particularly under pathological conditions such as gastroesophageal reflux disease (GERD). Herein, In vitro corrosion behavior of Ti-6Al-4 V over a 240-hour immersion period at 37 °C in artificial saliva simulating GERD, with pepsin and Candida albicans, both individually and combined. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization revealed that pepsin significantly improved corrosion resistance, achieving a maximum inhibition efficiency (IE) of 87.4%, while C. albicans showed a time-dependent decline in protection, with lower IE 71.8%. The combined presence of both agents further reduced IE to 55.6%, indicating a complex synergistic effect accelerating corrosion. Surface characterization by scanning electron microscopy (SEM) confirmed biofilm formation and surface degradation. Response Surface Methodology (RSM) modeling identified immersion time and component interactions as key factors influencing corrosion behavior. These findings offer novel insights into the interplay among enzymatic activity and microbial colonization, highlighting clinical implications for implant stability in GERD-affected oral environments.