Metal-Based Implants: Review of Materials and Designs

The purpose of implants is to replace, restore, maintain or improve the functionality of various tissues and organs of the human body. Their use in modern medicine has significantly improved treatment methods and increased the quality and life expectancy of patients. The most preferable from the point of view of the possibility of imparting the required mechanical properties, the relatively low cost of the material and low production costs are metal implants. Metals and their alloys in the production of implants are superior to ceramic and polymer materials in a range of properties such as tensile strength, endurance limit, wear resistance, hardness, elasticity, viscosity, shape memory effect. The paper provides an overview of the designs of modern implants for various purposes and the metal materials used for their production. An analysis of literature sources has shown that modern implants made of metal materials represent a wide range and have significant differences in shape and size. Some of them are characterized by a small cross-section and rigidity, while possessing elastic properties. Other products are load-bearing, in some cases massive, structures. According to the proposed classification, according to their purpose, metal implants are divided into: dental, cranial, maxillofacial, vertebral, traumatological, cardiovascular and joint endoprostheses. An analysis of the advantages and disadvantages of the main metal materials used in the production of implants (corrosion-resistant steel, titanium and titanium alloys, cobalt-chromium alloys and nitinol) has been performed. It has been established that all currently used biocompatible metal materials are not completely inert towards the body. Each material in any case causes some reaction in the surrounding tissues. The greatest biocompatibility and corrosion resistance in the body is provided by technical titanium, which, however, has low strength characteristics.