Classes of Materials Used in Medicine Flashcards
Classification of materials: conventional, novel
- ceramics
- metals
- polymers (synthetic and natural)
- composites
- Nanomaterial
- Smart material (able to respond to environment such as chemicals, environmental sensitive polymers)
Ceramics
inorganic compounds contain metallic and non-metallic elements, for which interatomic bonding is ionic or covalent, and which are generally formed at high temperatures
most ceramics occur as minerals, mostly silicon and aluminum
Ceramics advantages
- inert or bioactive in body
- high wear resistance (orthopedic and dental applications)
- high modulus and compressive strength
- esthetic properties
Ceramic disadvantages
- brittle
- low tensile strength
- poor fatigue
Ceramic applications
- femoral heads and cup inserts for ceramic on polyethylene
- ceramic on ceramic hip replacement bearings
- knee prostheses
- spinal fusion devices
- orthopedic instrumentation - dental-crowns
- bridges, implants and caps
- inner ear implants (cochlear implants)
- drug delivery devices
Nearly bioinert ceramtics
Alumina (Al2O3) and Zirconia (ZnO2) ceramics
hydroxyapatite (bioactive)
low strength but useful as coating for metallic implants, aids in tissue fixation of the implant by providing a porous surface and its surrounding tissue
Metals
closely packed crystal structure, valuable as load-bearing implants as well as internal fixation devices
Metal characteristics
high tensile strength, fatigue, and yield strength, low reactivity
Metal complication
Stress shielding
in hip implantation: the high strength of the metal in the impact induces it to assume more than its share of responsibility for the load in that region decreasing the load born by the surrounding tissue and therefore shielding it from experiencing stress causing bone density to decrease as bone tissue resorbs, cause complications in the implant/tissue
Metal applications
medical tubing, stents, catheters
Polymers
consist of small repeating units strung together in long chain, largest class of biomaterials, flexible structure enables it to be useful in applications from plastic garbage bags to rubber tires, adjusting the length of the chain and produce different properties with different applications
Polymer characteristics
- Hydrophilic
- Hydrophobic
- Biostable
- Biodegradable
- Natural
- Synthetic
- Highly processable
Composites vs other materals
- provide improved properties that typical metals, polymers, and ceramics alone cannot provide
- combine strength and flexibility by reinforcing a relatively flexible material with a harder, stronger one
- properties can be tailored by changing the composition ratio
- desirable for applications ranging from orthopedics, dentistry, and drug delivery to frontiers such as cancer theranostics
Composites
formed by combining multiple components of materials, such as metals, polymers, and ceramics; incorporates the desired characteristics of different materials to meet the stringent demands of living tissue
Bioactive materials vs biointertness
play a more aggressive role in the body. While a biocompatible material should affect the equilibrium of the body as little as possible, a bioactive material recruits specific interactions between the material and surrounding tissue.
Bioactive Materials
- encourage tissue integration to aid in the fixation of an implant in the body.
- a porous coating of Hydroxyapatite (HA), a normal component of bone, to help permanently stabilize the stem of the implant in the bone. The coating encourages ingrowth from the surrounding tissue that interlocks within the pores much like the pieces of a puzzle lock together.
Which ceramic material, known for its composition similar to bone mineral, is primarily used to promote bone growth in grafting procedures?
A) Zirconia B) Alumina C) Silicon carbide D) Hydroxyapatite
D) hydrozxyapatite
Considering factors like strength and resistance to body fluids, which metal alloy would be the optimal choice for constructing long-term orthopedic implants? A) Stainless steel B) Aluminum alloy C) Copper alloy D) Zinc alloy
A) stainless steel
Given its properties of biodegradability and compatibility, which polymer would be most suitable for developing temporary surgical sutures? A) Polyethylene (PE) B) Poly(lactic acid) (PLA) C) Polyvinyl chloride (PVC) D) Polymethyl methacrylate (PMMA)
B) Poly(lactic acid) (PLA)
Composite materials are used in dental applications. What is the primary function of the matrix component in a dental composite? A) To provide hardness B) To bond the filler particles together C) To act as a filler D) To enhance thermal conductivity
B) to bond the filler particles together (picture on slide with composites)
polymer processing for dental application
after implantation, interacts with living tissue, particles diffuse out of composite into living tissue to stimulate bone growth, the surrounding tissue will interact with the composite and may be able to interact
Requirements of biomaterials
- inert or specifically interactive
- biocompatible with the physiological context
- mechanically and chemically stable or
- biodegradable
- processable (for manufacturability)
- nonthrombogenic (if blood-contacting)
- sterilizable
