The use of electrochemical techniques to evaluate the corrosion performance of metallic biomedical materials and devices

The Mechanism of Metallosis After Total Hip Arthroplasty

Metallosis is defined as the accumulation and deposition of metallic particles secondary to abnormal wear from prosthetic implants that may be visualized as abnormal macroscopic staining of periprosthetic soft tissues. This phenomenon occurs secondary to the release of metal ions and particles from metal-on-metal hip implants in patients with end-stage osteoarthritis. Ions and particles shed from implants can lead to local inflammation of surrounding tissue and less commonly, very rare systemic manifestations may occur in various organ systems. With the incidence of total hip arthroplasty increasing as well as rates of revisions due to prosthesis failure from previous metal-on-metal implants, metallosis has become an important area of research. Bodily fluids are electrochemically active and react with biomedical implants. Particles, especially cobalt and chromium, are released from implants as they abrade against one another into the surrounding tissues. The body’s normal defense mechanism becomes activated, which can elicit a cascade of events, leading to inflammation of the immediate surrounding tissues and eventually implant failure. In this review, various mechanisms of metallosis are explored. Focus was placed on the atomic and molecular makeup of medical implants, the component/surgical associated factors, cellular responses, wear, tribocorrosion, joint loading, and fluid pressure associated with implantation. Current treatment guidelines for failed implants include revision surgery. An alternative treatment could be chelation therapy, which may drive future studies.

Arthroplasty is an invasive procedure which disrupts surrounding joint tissues, and can greatly perturb the joint’s immune homeostasis. In some instances, this may pose a difficult challenge to implant integration. Particles released from implants into the surrounding joint tissues activate the body’s defense mechanism, eliciting a cascade of events, which leads to biotribocorrosion and electrochemical attacks on the implant. This process may lead to the release of even more particles. Besides, implant makeup and designs, frictions between bearing surfaces, corrosion of non-moving parts with modular junctions, surgical mistakes, patient factor, comorbidities, and loosened components can alter the expected function of implants. High accumulations of these ions and particulates result in metallosis, with accompanying adverse complications. Current recommended treatment for failed prosthesis is revision surgeries. However, chelation therapy as a prophylactic intervention may be useful in future efforts but more investigation is required.

Effect of Protein and Mechanical Strain on the Corrosion Resistance and Cytotoxicity of the Orthodontic Composite Arch Wire

In this study, the effects of the exposure to different types of salivary proteins (fibrinogen, IgG, and mucin) and application of an in vitro bending strain on the laser welding orthodontic composite arch wire (CAW) were investigated, and the resultant corrosion behavior and cytotoxicity were studied in vitro. The purpose was to determine the mechanisms by which protein exposure and bending loads contribute to the corrosion of the CAW either alone or in combination by mimicking the clinical application. The results showed that the application of a mechanical strain significantly decreased the corrosion resistance of the CAW and increased the release of toxic corrosion products. The addition of the proteins inhibited the corrosion of the CAW, but the mechanical loads counteracted this effect. Mucin enhanced the corrosion resistance of the CAW. The effects of the proteins or strain, either alone or in combination, should be considered in the application of medical materials of heterogenetic alloys.