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

Ana Mellado-Valero,Anna Muñoz,Virginia Pina,Ma Sola-Ruiz

doi:10.3390/ma11010171

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.

Highlights

Galvanic corrosion occurs when dissimilar alloys are placed in direct contact within the oral cavity or within the tissues
In the case of dental implants, complicated electrochemical processes related to implant and suprastructure are linked to galvanic corrosion [1,2] which leads to a clinically relevant situation due to two main reasons: the biological effects that may result from the dissolution of alloy components, and the bone destruction caused by the current flow that results from galvanic coupling
The aim of this study is to analyse the electrochemical behaviour in artificial saliva (AS) of cobalt-chromium alloys (CoCr), nickel-chromium-titanium (NiCrTi), gold-palladium alloy (Au) and titanium alloy (Ti6Al4V), used in the manufacture of the implant prosthesis structures and to evaluate the galvanic effect produced by the contact of those with the commercially pure titanium grade 2 (TiG2)

Summary

Introduction

Galvanic corrosion occurs when dissimilar alloys are placed in direct contact within the oral cavity or within the tissues. When saliva penetrates into prosthetic components in contact with implants, the metal dissolution generates currents, due to a potential difference created by the formation of a galvanic cell (Figure 1). In the case of dental implants, complicated electrochemical processes related to implant and suprastructure are linked to galvanic corrosion [1,2] which leads to a clinically relevant situation due to two main reasons: the biological effects that may result from the dissolution of alloy components, and the bone destruction caused by the current flow that results from galvanic coupling. Coupling could result in an electropositive local environment along the implant interface, which could directly influence bone resorption. These galvanic couplings should be avoided [3]

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