Determinants of corrosion resistance of Ti-6Al-4V alloy dental implants in an In Vitro model of peri-implant inflammation

Abstract

BackgroundTitanium (Ti) and its alloys possess high biocompatibility and corrosion resistance due to Ti ability to form a passive oxide film, i.e. TiO2, immediately after contact with oxygen. This passive layer is considered stable during function in the oral cavity, however, emerging information associate inflammatory peri-implantitis to vast increases in Ti corrosion products around diseased implants as compared to healthy ones. Thus, it is imperative to identify which factors in the peri-implant micro-environment may reduce Ti corrosion resistance.MethodsThe aim of this work is to simulate peri-implant inflammatory conditions in vitro to determine which factors affect corrosion susceptibility of Ti-6Al-4V dental implants. The effects of hydrogen peroxide (surrogate for reactive oxygen species, ROS, found during inflammation), albumin (a protein typical of physiological fluids), deaeration (to simulate reduced pO2 conditions during inflammation), in an acidic environment (pH 3), which is typical of inflammation condition, were investigated. Corrosion resistance of Ti-6Al-4V clinically-relevant acid etched surfaces was investigated by electrochemical techniques: Open Circuit Potential; Electrochemical Impedance Spectroscopy; and Anodic Polarization.ResultsElectrochemical tests confirmed that most aggressive conditions to the Ti-6Al-4V alloy were those typical of occluded cells, i.e. oxidizing conditions (H2O2), in the presence of protein and deaeration of the physiological medium.ConclusionsOur results provide evidence that titanium’s corrosion resistance can be reduced by intense inflammatory conditions. This observation indicates that the micro-environment to which the implant is exposed during peri-implant inflammation is highly aggressive and may lead to TiO2 passive layer attack. Further investigation of the effect of these aggressive conditions on titanium dissolution is warranted.

The Influence of ZnO Oxide Layer on the Physicochemical Behavior of Ti6Al4V Titanium Alloy

“…However, interference with the human body environment disturbs its existing state of balance and thus triggers defense reactions, such as decreased pH of body solution and increased temperature. In some reports, in order to simulate relevant clinical scenarios, the pH of the solution was decreased by the addition of fluoride ions [ 32 , 33 ]. However, there is no clear information about the influence of chloride ions on the corrosive behavior of titanium alloys.…”

Novel Coatings to Minimize Corrosion of Titanium in Oral Biofilm

“…The mechanical stress from chewing and the saliva’s chemical environment can wear down or dissolve the oxide layer over time. Once the TiO 2 layer is broken down, this layer will not regenerate on the surface, rendering titanium as prone to corrosion as many other base metals [ 23 , 26 ]. To further improve the material’s longevity, thus preventing peri-implantitis, one of the significant strategies focuses on minimizing bacterial adhesion on the dental implant material.…”

Electrochemical Behavior of Ti6Al4V Alloy Used in Dental Implants Immersed in Streptococcus gordonii and Fusobacterium nucleatum Solutions

“…The titanium alloys used in dental implants and evaluated in Afnor artificial saliva have a passivation behavior in the anodic branch [ 38 ], similar to that found in Ringer’s lactate tests. The TiO 2 film possesses a high corrosion resistance in various test solutions, such as artificial saliva, Ringer’s solution, 0.9% NaCl solution, or physiological saline solution [ 61 , 62 ]. The comparison of the electrochemical behavior identified by the potentiodynamic polarization tests is notable in the anodic branch when artificial solutions or bacteria are used.…”