Improved tribocorrosion performance of bio-functionalized TiO2 nanotubes under two-cycle sliding actions in artificial saliva

Abstract

After insertion into bone, dental implants may be subjected to tribocorrosive conditions resulting in the release of metallic ions and solid wear debris, which can induce to peri-implant inflammatory reactions accompanied by bone loss, and ultimately implant loosening. Despite the promising ability of TiO nanotubes (NTs) to improve osseointegration and avoid infection-related failures, the understanding of their degradation under the simultaneous action of wear and corrosion (tribocorrosion) is still very limited. This study aims, for the first time, to study the tribocorrosion behavior of bio-functionalized TiO NTs submitted to two-cycle sliding actions, and compare it with conventional TiO NTs. TiO NTs grown by anodization were doped with bioactive elements, namely calcium (Ca), phosphorous (P), and zinc (Zn), through reverse polarization anodization treatments. Characterization techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM), were used to characterize the films. Tribocorrosion tests were carried out in artificial saliva (AS) by applying two cycles of reciprocating sliding actions. The open circuit potential (OCP) was monitored before, during, and after both cycles of sliding, during which the coefficient of friction (COF) was calculated. The resulting wear scars were analyzed by SEM and EDS, and wear volume measurements were performed by 2D profilometry. Finally, the mechanical features of TiO NTs were accessed by nanoindentation. The results show that bio-functionalized TiO NTs display an enhanced tribocorrosion performance, ascribed to the growth of a nano-thick oxide film at Ti/TiO NTs interface, which significantly increased their adhesion strength to the substrate and consequently their hardness. Furthermore, it was discovered that during tribo-electrochemical solicitations, the formation of a P-rich tribofilm takes place, which grants both electrochemical protection and resistance to mechanical wear. This study provides fundamental and new insights for the development of multifunctional TiO NTs with long-term biomechanical stability and improved clinical outcomes.

Progression of Bio-Tribocorrosion in Implant Dentistry

“…After screening full texts, a total of 44 studies were included considering the tribocorrosion analyses for dental implants and frameworks applications. The characteristics of the 44 studies (Vieira et al, 2006;Banu et al, 2008;Richard et al, 2010;Souza et al, 2010aSouza et al, , 2012Sivakumar et al, 2011;Dimah et al, 2012;Mardare et al, 2012;Mathew et al, 2012a,b;Albayrak et al, 2013;Alves et al, 2013Alves et al, , 2014Alves et al, , 2017Alves et al, , 2018Benea et al, 2013Benea et al, , 2015Benea et al, , 2017Licausi et al, 2013a,b;Fazel et al, 2015;Figueiredo-Pina et al, 2015;Golvano et al, 2015;Oliveira et al, 2015;Buciumeanu et al, 2016Buciumeanu et al, , 2017Correa et al, 2016;Guinon Pina et al, 2016;Marques et al, 2016;Mindivan et al, 2016;Pontes et al, 2016;Sampaio et al, 2016b;Silva et al, 2016;Bryant and Neville, 2017;Danaila and Benea, 2017;Mindivan and Mindivan, 2018;Sikora et al, 2018;Trino et al, 2018;Wang et al, 2018;Branco et al, 2019;Corne et al, 2019;Cui et al, 2019a,b;…”

Advanced Surface Treatments on Titanium and Titanium Alloys Focused on Electrochemical and Physical Technologies for Biomedical Applications

“…Therefore, tribocorrosion studies become of fundamental importance, not only because of the high probability of adhesion failure of the nanotubular systems, but also because of their high clinical relevance, since implant degradation in vivo can seriously compromise osseointegration or even its long-term stability. In the attempt to construct effective nanotubular systems based on an integrated and multidisciplinary approach that addresses the development of tribocorrosion resistant implant surfaces with potential to avoid infection, and simultaneously, promote osseointegration, Alves and co-workers have recently reported, for the first time, important findings on the tribocorrosion field [101,102].…”

“…The adhesion properties and degradation mechanisms of TiO 2 NTs were investigated by tribo-electrochemical tests carried out in AS under single and multiple sliding actions, to better mimic real in vivo conditions that dental implants might be exposed to in real life [101,102]. From these studies the poor adhesion of conventional TiO 2 NTs was undoubtedly confirmed, and bio-functionalization came out as a very promising approach to overcome it.…”

“…An additional important outcome from the study performed by Alves et al [102], is the ability of TiO 2 NTs to induce the formation of a protective P-rich tribo-film with lubricating properties during tribo-electrochemical solicitations. This film may help to explain the open circuit potential (OCP) evolution during sliding, both for conventional and bio-functionalized NTs, as well as the high electrochemical stability observed in both cases when submitted to multiple sliding actions.…”

“…These results highlight the ability of NTs to withstand multiple cycles of mechanical solicitations, and suggest that the degradation induced by mechanical wear in the beginning of sliding actions, dictate their long-term degradation. This ability of nanotubular films to avoid further mechanical degradation as long mechanical solicitations take place, is believed to be strongly related with the formation of the compact P-rich tribo-film, which grants both protection against corrosion and wear [101,102].…”