Bio Tribocorrosion In Biomaterials And Medical Implants

Two materials (one being metal) under slight relative motion in a liquid medium are subjected to fretting corrosion. This chapter is dedicated to studying fretting corrosion of implants. After describing the most significant implants subjected to fretting, fretting corrosion is defined. Fretting corrosion is a particular degradation mechanism; it highlights the key role of passive film, crevice corrosion, etc. For demonstrating the electrochemical effect of the fretting corrosion of metal, some investigations are presented at free corrosion potential and at applied potential to measure the specific current density. Moreover, the role of proteins is investigated because they constitute the biological environment and thus play a significant role in fretting corrosion processes. Finally, results from atomic force microscopy (AFM) show the particular debris, size about 100nm. The problem of debris influence is discussed.

During their service life, most biomaterials and medical implants are vulnerable to tribological damage. In addition, the environments in which they are placed are often corrosive. The combination of triobology, corrosion and the biological environment has been named ‘bio-tribocorrosion’. Understanding this complex phenomenon is critical to improving the design and service life of medical implants. This important book reviews recent key research in this area. After an introduction to the topography of bio-tribocorrosion, Part one discusses different types of tribocorrosion including fatigue-corrosion, fretting-corrosion, wear-corrosion and abrasion-corrosion. The book also discusses the prediction of wear in medical devices. Part two looks at biological effects on tribocorrosion processes, including how proteins interact with material surfaces and the evolution of surface changes due to bio-tribocorrosion resulting from biofilms and passive films. Part three reviews the issue of bio-tribocorrosion in clinical practice, including dental applications and joint replacement as well the use of coatings and test methods for bio-tribocorrosion. With its international team of contributors, Bio-tribocorrosion in biomaterials and medical implants is a standard reference for those researching and developing medical devices as well as clinicians in such areas as dentistry and orthopaedic surgery. Reviews recent research in bio-tribocorrosion and its role in improving the design and service life of medical implants Discusses types of bio-tribocorrosion including fatigue and wear corrosion Examines biological effects on bio-tribocorrosion processes including interaction of proteins with metal surfaces

Wear can be defined as a process where interaction between two surfaces or bounding faces of solids within the working environment results in dimensional loss of one solid, with or without any actual decoupling and loss of material. Wear may accelerate corrosion that involves chemical or electrochemical reactions between materials. Both these phenomena fall under the broader category of tribocorrosion. The interactions of mechanical loading and chemical/electrochemical reactions that occur between the elements of a tribological system exposed to biological environments constitute bio-tribocorrosion science.

The tribological performance of implant materials within the body where the pH can vary between 7.4 and 4.0, depending on whether the joint is infected or not, is extremely harsh and varies significantly from that experienced in other engineering environments. Three wear mechanisms that affect biomedical and, in particular, orthopaedic implants are regularly reported. These are adhesion, abrasion and fatigue. The wear mechanisms in biomedical implants, particularly hip joints, are reported to be a function of the following variables: type of materials used, contact stresses, lubricants and clearance, surface hardness and roughness, type of articulation due to motion, number of cycles, solution particle count and distribution, and tribocorrosion.

In this chapter, a general overview of current dental implants is presented, identifying weak points where improvements can be made. Particular importance is given to the surface properties of materials susceptible to modifications for improving the biological response for the specific application. Then, the concepts and techniques relevant for the evaluation of the physico-chemical properties and the protein adsorption, biocompatibility, bioactivity and biofilm formation are described. The chapter describes a particular method to modify the chemical and physical properties of materials, known as magnetron sputtering. Finally, an example using Nb2O5 coatings is presented, where also corrosion resistance and adhesion results are included.

Articulating systems are complex mechanical systems operating under sliding, rotation, slip, vibrations, weight bearing, and loading conditions. A problem in mechanical systems is the occurrence of tribocorrosion, involving a synergism between corrosion and mechanical wear, and causing increased material degradation. A tribocorrosion protocol allowing separation of the mechanical, corrosive and synergetic contributions to the total loss of material is described, based on electrochemical measurements performed before and during unidirectional sliding. As a case study, the protocol is implemented to test the tribocorrosion resistance of CoCrMo alloys under sliding. The different components of the total wear related to corrosive and mechanical contributions are calculated.

This chapter discusses synergistic damage mechanisms of modular implants due to mechanical stimulus and electrochemical dissolution. The influences of contact loads, plastic deformation, residual stresses, and environmental conditions are focused to illustrate mechanisms of damage and dissolution. Fretting corrosion is the most prevalent phenomenon that degrades the mechanical and chemical properties of implant materials. It has been explained as an alternating process of fracture and unstable growth of metal oxide film during fatigue contact motion in the corrosive environment. Stress-dependent electrochemical dissolution has also been identified as one of the key mechanisms governing surface degradation in fatigue contact and crevice corrosion of biomedical implants. This damage mechanism incorporates contact-induced residual stress development and stress-assisted dissolution. Understanding of the corrosion damage mechanism of metallic implants is very important in predicting the useful life of implants and optimizing the design of orthopedic implants.

Total joint replacement (TJR) is one of the success stories of modern medicine, which has reliably provided dramatic pain relief and improved the quality of life for several million patients with a destructive end-stage joint disease. However, the main long-term complication of TJR surgery is prosthetic loosening, often combined with osteolysis following wear, corrosion and failure of the implant. Over the past decade, the biological interactions between various types of wear particles and metal ions from metal-on-polyethylene (MoPE), metal-on-metal (MoM) and ceramic-on-ceramic (CoC) implants, endogenous danger signals (alarmins) and/or bacterial components of the microbiome with the innate and adaptive host defence (immune) system, have become better known. In this chapter, we discuss the role of biomaterials and implant-derived wear and corrosion debris in loosening of TJRs, with particular emphasis on MoM total hip replacements (THR) and hip resurfacing arthroplasty (HRA).