Electrochemical Behaviour and Galvanic Effects of Titanium Implants Coupled to Metallic Suprastructures in Artificial Saliva

Abstract

The aim of the present study is to analyze the electrochemical behavior of five different dental alloys: two cobalt-chromium alloys (CoCr and CoCr-c), one nickel-chromium-titanium alloy (NiCrTi), one gold-palladium alloy (Au), and one titanium alloy (Ti6Al4V), and the galvanic effect when they are coupled to titanium implants (TiG2). It was carried out by electrochemical techniques (open circuit measurements, potentiodynamic curves and Zero-Resistance Ammetry) in artificial saliva (AS), with and without fluorides in different acidic conditions. The studied alloys are spontaneously passivated, but NiCrTi alloy has a very narrow passive domain and losses its passivity in presence of fluorides, so is not considered as a good option for implant superstructures. Variations of pH from 6.5 to 3 in artificial saliva do not change the electrochemical behavior of Ti, Ti6Al4V, and CoCr alloys, and couples, but when the pH of the artificial saliva is below 3.5 and the fluoride content is 1000 ppm Ti and Ti6Al4V starts actively dissolving, and CoCr-c superstructures coupled to Ti show acceleration of corrosion due to galvanic effects. Thus, NiCrTi is not recommended for implant superstructures because of risk of Ni ion release to the body, and fluorides should be avoided in acidic media because Ti, Ti6Al4V, and CoCr-c superstructures show galvanic corrosion. The best combinations are Ti/Ti6Al4V and Ti/CoCr as alternative of noble gold alloys.

Bioactive Coating on Titanium Dental Implants for Improved Anticorrosion Protection: A Combined Experimental and Theoretical Study

“…A large-area Pt electrode served as a counter electrode and a reference electrode, to which all potentials in the paper are referred, was an Ag|AgCl, 3.0 mol dm −3 KCl (E = 0.210 V vs. standard hydrogen electrode, SHE). Barrier properties of unmodified and modified Ti-implants were evaluated in solution based on Fusayama artificial saliva (0.4 g dm −3 NaCl, 0.4 g dm −3 KCl, 0.6 g dm −3 CaCl 2 ·2H 2 O, 0.58 g dm −3 Na 2 HPO 4 ·2H 2 O, and 1 g dm −3 urea), pH 6.8 [23], prepared from p.a. grade chemicals and redistilled water.…”

Corrosion of Metallic Biomaterials: A Review

“…On the other hand, 316L stainless steel is susceptible to pitting corrosion when it is coupled to either Ti- or Co-based alloys [300]. Mellado-Valero et al [301] analysed the galvanic corrosion of CoCr, CoCr-c, NiCrTi, Au-Pd and Ti–6Al–4V dental alloys for implant superstructures when coupled to Ti grade 2 implants in artificial saliva (AS), with and without fluorides in different acidic conditions. It was concluded that NiCrTi is not recommended for implant superstructures due to the risk of Ni ion release to the body and that fluorides should be avoided in acidic media because Ti, Ti–6Al–4V and CoCr-c superstructures show galvanic corrosion.…”

A New Insight into Coating’s Formation Mechanism Between TiO2 and Alendronate on Titanium Dental Implant

“…The method of electrochemical impedance spectroscopy (EIS) was applied to investigate the implant stability during exposure to a Fusayama artificial saliva solution (0.4 g dm −3 NaCl, 0.4 g dm −3 KCl, 0.6 g dm −3 CaCl 2 •2H 2 O, 0.58 g dm −3 Na 2 HPO 4 •2H 2 O, and 1 g dm −3 urea; pH 6.8 [46]) at the open circuit potential (E OCP ). The implant sample served as a working electrode (an area of 0.98 cm 2 ), an Ag|AgCl, 3.0 mol dm −3 KCl (E = 0.210 V vs. standard hydrogen electrode (SHE)) as a reference, and a platinum plate as a counter electrode.…”