Polymers offer a wide range of choices for medical applications because of their versatility in properties and processing. This article provides an overview of polymeric materials and the characteristics that make them a unique class of materials. It describes the ways to classify polymers, including the polymerization method, how the material deforms, or molecular origin or stability. The article contains tables that list common medical polymers used in medical devices. It describes the medical polymer selection criteria and regulatory aspects of materials selection failure analysis and prevention. Failure analysis and prevention processes to determine the root cause of failures that arise at different stages of the product life cycle are reviewed. The article describes the mechanisms of plastic product failure analysis. It discusses the trends in the use of medical polymers, such as high-performance polymers for implants, tissue engineering, and bioresorbable polymers.

This article outlines some of the selection criteria for choosing an implant material for biomedical devices in orthopedic, dental, soft-tissue, and cardiovascular applications. It details the development of implants based on materials, such as metallic implants, ceramic implants, and polymeric implants. The article discusses the specific problems associated with implant manufacturing processes and the consequent compromises in properties of functionally graded implants. It describes the manufacturing of the functionally-graded hip implant by using the LENS process. It reviews the four different types of tissue responses to the biomaterial. The article discusses the testing of implant failure, such as in vitro and in vivo assessment of tissue compatibility.

This article provides a summary of biocompatibility or biological response of metals, ceramics, and polymers used in medical implant, along with their clinical issues. The polymers include ultrahigh-molecular-weight polyethylene, nonresorbable polymer, and resorbable polymers.

This article tabulates materials that are known to have been used in orthopaedic and/or cardiovascular medical devices. The materials are grouped as metals, ceramics and glasses, and synthetic polymers in order. These tables were compiled from the Medical Materials Database which is a product of ASM International and Granta Design available by license online and as an in-house version. The material usage was gleaned from over 24,000 U.S. Food and Drug Administration (USFDA), Center for Devices and Radiological Health, Premarket notifications (510k), and USFDA Premarket Approvals, and other device records that are a part of this database. The database includes other material categories as well. The usage of materials in predicate devices is an efficient tool in the material selection process aiming for regulatory approval.

The biocompatibility of a material relates to its immunological response, toxicity profile, and ability to integrate with surrounding tissue without undesirable local or systemic effects on a patient. This article underscores the transformation of the medical device design ecosystem engaged as an integral part of the device ecosystem. It discusses the various applications of biomaterials, including orthopedic, cardiovascular, ophthalmic, and dental applications. The article describes the four major categories of biomaterials, such as metals, polymers, glass and ceramics, and composites. A discussion on natural materials, nanomaterials, and stem cells is also provided. The article concludes with information on examples of biomaterials applications, including endovascular devices, knee implants, and neurostimulation.

This article discusses the several aspects of biocompatibility of polymers, including selection of a suitable polymer, specific use of a material, contact of polymer on body site, and duration of the contact. It describes factors influencing the biological response to the polymer in a biocompatibility perspective. These include raw materials, manufacturing process, cleaning and sterilization, and biodegradation and biostability. The article reviews the general testing of polymer, such as chemical, mechanical and thermal tests, to ensure that the polymer is stable and has not been adversely altered due to sterilization or processing. It concludes with a description of the guidance, provided by the regulatory authorities, on the biocompatibility testing of polymers and polymer-containing devices that can aid in selecting the right analysis.

This article provides the background of biological evaluation of medical devices. It discusses what the ISO 10993 standards require for polymeric biomaterials and presents examples of what qualitative and quantitative tests can be used to satisfy the requirements. The article describes infrared (IR) analysis and thermal analyses that are used extensively to fingerprint polymeric materials and should be a part of all polymeric biomaterials characterization programs. It also provides a discussion on the chemical characterization and risk assessment of extracts. Background information on risk assessments of extracts is also included. The four basic steps that are commonly used in the risk assessment process are discussed. These steps include hazard identification, dose-response assessment, and exposure assessment, and risk characterization.

This article provides an overview of curing techniques, adhesive chemistries, surface preparation, adhesive selection, and medical applications for adhesives. The curing techniques are classified into moisture, irradiation, heat, and anaerobic. The article highlights the common types of curable adhesives used for medical device assembly, including acrylics, cyanoacrylates, epoxies, urethanes, and silicones. Other forms of adhesives, such as hot melts, bioadhesives, and pressure-sensitive adhesives, are also discussed. Adhesives are used for medical device assembly, hard-tissue attachment in the fields of orthopedics and dentistry, and soft-tissue attachment such as wound closure. The typical characteristics and applications of biocompatible medical device adhesives are listed in a table. The article concludes with a section on selection of materials for medical adhesives.

Total joint replacement in orthopedic surgery can be achieved by excision, interposition, and replacement arthroplasty. This article details the most common materials used in total replacement synovial joints, such as metals, ceramics, and ultrahigh molecular weight polyethylene (UHMWPE). The principal physical properties and tribological characteristics of these materials are summarized. The article discusses the pin-on-disk experiments and pin-on-plate experiments for determining friction and wear characteristics. It details the use of various types of joint simulators, such as hip joint simulators and knee joint simulators, to evaluate the performance of engineering tribological components in machine simulators. The article describes in vivo assessment of total joint replacement performance.

This article focuses on the modes of operation, physical basis, sample requirements, properties characterized, advantages, and limitations of common characterization methods that are used to evaluate the physical morphology and chemical properties of component surfaces for medical devices. The methods include light microscopy, scanning electron microscopy, atomic force microscopy, energy-dispersive x-ray spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy.

This article addresses the biologic aspects of implant debris both locally and systemically. It discusses the particulate debris, such as stainless steel, cobalt alloy, and titanium alloy, and soluble debris obtained due to wear from all orthopedic implants. Implant debris is known to cause local inflammation, local osteolysis, and, in some cases, local and systemic hypersensitivity. The article describes debris-induced local effects, particle-induced proinflammatory responses, and debris-induced systemic effects. It concludes with a discussion on the four systemic effects of implant debris, namely, neuoropathic effects, hypersensitivity effects, carcinogenictiy, and general toxicity.

Ceramics are used widely in a number of different clinical applications in the human body. This article provides a brief history of the bioceramics field and information on the classification of the different types of bioceramics. These include bioinert ceramics, bioactive ceramics, and bioresorbable ceramics. The article describes the third-generation bioceramics, classified by Hench and Polak, such as silicate-substituted hydroxyapatite and bone morphogenic protein-carrying calcium phosphate coatings. It reviews several examination methods that are used to test the biocompatibility of ceramics, namely, biosafety testing, biofunctionality testing, bioactivity testing, and bioresorbability testing.

This article focuses on the use of noble and precious metals for biomedical applications. The noble metals include gold, platinum, palladium, ruthenium, rhodium, iridium, and osmium. The physical and mechanical properties of the noble and precious metals are presented in tables. A brief discussion on the ancient history of noble and precious metal use in dentistry is provided. The article discusses the use of direct gold dental filling materials, direct silver dental filling materials, traditional amalgam alloys, high-copper amalgam alloys, and gallium alloys in biomedical applications. Modern stents were developed as a result of balloon catheterization research. The article describes gold coatings and iridium oxide coatings for stents.

Physically, tantalum is a dark, blue-gray, lusterless metal that exists in two crystalline forms: an alpha-phase with a body-centered cubic structure, and a brittle beta-phase with a tetragonal orientation. This article tabulates the physical and material properties of tantalum. It discusses the use of tantalum in medical electronics and the advantage of tantalum over stainless steel. The article describes the manufacturing and medical applications of tantalum foam.

This article focuses on the specific aspects of nitinol that are of interest to medical device designers. It describes the physical metallurgy, physical properties, and tensile properties of the nitinol. The article discusses the factors influencing superelastic shape memory effects, fatigue, and corrosion in medical device design. It reviews the biocompatibility of nitinol based on corrosion behavior. The article describes the general principles, potential pitfalls, and key properties for manufacturing, heat treatment, and processing of nitinol.

Fatigue failure of engineering components and structures results from progressive fracture caused by cyclic or fluctuating loads. Fatigue is an important potential cause of mechanical failure, because most engineering components or structures are or can be subjected to cyclic loads during their lifetime. This article focuses on fractography of fatigue. It provides an abbreviated summary of fatigue processes and mechanisms: fatigue crack initiation, fatigue crack propagation, and final fracture,. Characteristic fatigue fracture features that can be discerned visually or under low magnification are then described. Typical microscopic features observed on structural metals are presented subsequently, followed by a brief discussion on fatigue in polymers and polymer-matrix composites.

Polyurethane is any polymer consisting of a chain of repeating organic units joined by urethane linkages. Polyurethane polymers are formed through step-growth polymerization by making a monomer containing at least two isocyanate functional groups to react with another monomer containing at least two hydroxyl (alcohol) groups. This article provides a detailed account of the protective coatings used in the building, infrastructure, and architectural markets. It focuses on the various types of polyurethane coatings used in these applications: moisture-cure and two-pack aromatic coatings as primers and topcoats, moisture-cure aromatic elastomeric high-build coatings, moisture-cure aliphatic topcoats, two-pack aliphatic polyurethane coatings as topcoats, and one- and two-pack polyurethane dispersion coatings as sealers and topcoats. It also includes a section on the health effects of isocyanates.

This article begins with an overview of the fundamentals of adhesive technology, including functions, limitations, adhesive joint types, and the key factors in the selection of adhesives, including application, type of joint, process limitation, mechanical requirement, and service conditions. It then focuses on the characteristics, types, and properties of the five groups of adhesives, such as structural, hot melt, pressure sensitive, water based, ultraviolet, and electron beam cured adhesives. The article also discusses the functions and applications of adhesive modifiers, including fillers, adhesion promoters, tackifiers, and tougheners. It gives a short note on functions of primers and primerless bonding. Applications of adhesives in automotive, aerospace, electronics, electrical, medical, sports, and construction sectors are also described. Finally, the article describes the steps in adhesive bonding, including storage and handling of adhesives, bonding preparation, adhesive application, tooling, and curing.

Structural applications for advanced ceramics include mineral processing equipment, machine tools, wear components, heat exchangers, automotive products, aerospace components, and medical products. This article begins with an overview of the wear-resistant applications and the parameters affecting wear of ceramics, namely, hardness, thermal conductivity, fracture toughness, and corrosion resistance. The next part of the article addresses temperature-resistant applications of advanced ceramics. Specific applications of ceramic materials addressed include cutting tools, pump and valve components, rolling elements and bearings, paper and wire manufacturing, biomedical implants, heat exchangers, adiabatic diesel engines, advanced gas turbines, and aerospace applications.

Biomaterials are the man-made metallic, ceramic, and polymeric materials used for intracorporeal applications in the human body. This article primarily focuses on metallic materials. It provides information on basic metallurgy, biocompatibility, chemistry, and the orthopedic and dental applications of metallic biomaterials. A table compares the mechanical properties of some common implant materials with those of bone. The article also provides information on coatings, ceramics, polymers, composites, cements, and adhesives, especially where they interact with metallic materials.