Interface Damage in Titanium Dental Implant Due to Tribocorrosion: The Role of Mastication Frequencies

Abstract

The aim of this study was to investigate the influence of fretting motions on the depassivation–repassivation processes occurring in Ti6Al4V alloy, at an in vitro simulated oral environment. Ti6Al4V discs were subjected to fretting–corrosion using a pin-on-disc tribometer. Specimens underwent 2000 motion cycles, with ± 500 µm of fretting stroke, and 8 N of load at frequencies of 1, 2, and 4 Hz. Surface characterization was performed using white-light interferometry and scanning electron microscope. Total mass loss (Kwc), and mass loss due to wear (Kw) and corrosion (Kc) were calculated. Lower potentials were reached at a frequency of 4 Hz. The coefficient of friction was statistically higher (p > 0.05) under 1 Hz (μ = 0.66) as compared to that of 2 and 4 Hz (μ = 0.53; μ = 0.51). Kwc was significantly higher (p < 0.001) on specimens subjected to a higher frequency of 4 Hz (16.1 μg), when compared to 1 and 2 Hz (0.30 μg; 1.24 μg). Under mechanical input, titanium’s oxide layer is constantly removed and reformed involving two processes called depassivation and repassivation. This study was conducted as a way to understand the influence of the mechanical stimuli alongside the oxide layer stability. The mechanical and chemical attacks encountered by Ti6Al4V vary regarding the fretting frequency applied. Lower fretting frequencies allow for the better chance of repassivation resulting in a protective barrier against degradation processes.