Titanium Corrosion Mechanisms in the Oral Environment: A Retrieval Study.

Danieli Rodrigues,Pilar Valderrama,Sathyanarayanan Sridhar,Arvind Adapalli,Anie Thomas,Maria Burbano,Kelli Palmer,Thomas Wilson,Chandur Wadhwani

doi:10.3390/ma6115258

Abstract

Corrosion of titanium dental implants has been associated with implant failure and is considered one of the triggering factors for peri-implantitis. This corrosion is concerning, because a large amount of metal ions and debris are generated in this process, the accumulation of which may lead to adverse tissue reactions in vivo. The goal of this study is to investigate the mechanisms for implant degradation by evaluating the surface of five titanium dental implants retrieved due to peri-implantitis. The results demonstrated that all the implants were subjected to very acidic environments, which, in combination with normal implant loading, led to cases of severe implant discoloration, pitting attack, cracking and fretting-crevice corrosion. The results suggest that acidic environments induced by bacterial biofilms and/or inflammatory processes may trigger oxidation of the surface of titanium dental implants. The corrosive process can lead to permanent breakdown of the oxide film, which, besides releasing metal ions and debris in vivo, may also hinder re-integration of the implant surface with surrounding bone.

Highlights

Titanium (Ti) and its alloys are broadly used in the design of dental and orthopedic implants, due to a combination of attractive properties that include high corrosion resistance, biocompatibility, re-passivation and adequate mechanical properties
The goal of this study is to evaluate the surface of retrieved titanium dental implants due to peri-implantitis
The observations of this study indicate that metal ions and debris originating from corrosion processes may promote adverse tissue reactions that could lead to peri-implantitis

Summary

Introduction

Titanium (Ti) and its alloys are broadly used in the design of dental and orthopedic implants, due to a combination of attractive properties that include high corrosion resistance, biocompatibility, re-passivation and adequate mechanical properties. The corrosion resistance of Ti and its alloys is a result of the material’s ability to spontaneously form passive oxide films (TiO2) when in contact with oxygen [1]. In the event of damage, TiO2 has the ability to spontaneously reform under normal physiological conditions. Events, such as abnormal cyclic loads, implant micromotion, acidic environments and their conjoint effects, can result in permanent breakdown of the oxide film, which may lead to exposure of the bulk metal to an electrolyte. Because the oral environment will subject titanium to conditions of varying pH, due to inflammatory or other processes that can turn the medium acidic, active dissolution of metal ions can occur upon exposure of the bulk metal [2,3,4]. The main events linked to Ti implant degradation in the oral environment seem to be related to: (1) electrochemical factors, acidity caused by the presence of inflammatory processes, oral bacteria or the use of solutions that can attack the surface of the implant; (2) mechanical factors, induced by mechanical loads that can lead to fretting and excessive wear of the surface; and (3) synergistic action of electrochemical and mechanical factors (tribocorrosion)

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Conclusion