Ceramic bio materials Flashcards
Define Ceramic
InOrganic, non metallic metal.
Crystaline compounds formed between metallic and nonmetallic elements
These crystals have strong bonds and are therefor hard
Glasses
Ceramic composition but not crystaline
Bioactive glasses work with the surface to form a calcium phosphate layer on their surface
- They are an inorganic melt colled to a solid form without crystalisation
- An amorphous (lacks long range order like you would expect in a solid) solid
Possesses short range atomic order –> therefor brittle
1st Generation Biomaterial
Bioinert- minimal interaction with the body tissues
Generally forms a fibrous capsule
Alumina, Zirconia
2nd Generation Biomaterial
Biodegradable (Resorbable)
This dissolves after a specific period of time ( need to ensure this is the required time )
Calcium phosphates and calcium sulphates
Bioactive - surface reactive
Tighly bonded to living tissues
Hydroxyapatite
3rd Generation Biomaterial
Scaffolds made of biologically active molecules
This stimulates living tissue regeneration
Bioglass
What type of biomaterial is calcium phosphate and give and example of how it is used
2nd Gen- Biodegradable
Used as bone graft substitute to replace bone loss
Why do we use bioceramics
Initially used instead of metals in order to increase biocompatability
Three basic types of biomaterial
- Bioactive
- BioInert
- Bioresorbable
What type of biomaterial is Glass ceramic and give and example of how it is used
Give definition
Give an example of a commercially available version
BioActive
Glass- ceramics - a polycrystaline solid prepared by controlled crystallisation of glass.
Vertibral prosthesis to replace those removed after surgery
- It was the first biomaterial to display bioactiviity in the bone system
-Capable of direct chemical bonding with the host tissue
- Stimulatory effects on bone building cells
- The structure does not shrink during crystalisation so the net glass shape is retained. This makes it good for non load baring implants such as maxillo facial repair.
Example: BioGlass which bonds well with bone. It is sometimes used ina powder form to encourage bone healing- occurs because it forms hydroxyapatite which encourages cell adhesion adn releases calcium.
Bioinert ceramics- most common example, uses and +ives
Alumina oxide Zirconia is also very popular for use in hip sockets Highly stable Good mechanical properties Good biocompatability Little fibrous capsule formation Non degradable Don't cause osteolysis
What ceramic is known as the ultimate ceramic and why
Current problems
How are we over coming them
Zirconia
It has great properties when dry- super strong
As soon as it gets wet it fails
Combining it with alumina means the new material has improved hardness and wear resistance. It also is provided with a high strength and density from the alumina.
Give an example of a bioactive ceramic
Calcium phosphates
These are good for coating and scaffold but have poor mechanical properties
Bone mineral is carbonated hydroxyapatate which is a type of calcium phosphate so this works well for scaffolding bone
What is the chemical formula for hydroxyapatate
Ca10(PO4)6(OH)2
What is an example of a hydroxyapatite ceramic and what are they good for
TRICALCIUM PHOSPHATE
- Highly resorbable
- Especially useful in cements
- Not good at load baring as resolution rate is so high
- If used individually, work well as coatings
- If mixed with other materials can be used for other things
What are the mechanical properties of glass ceramic influenced by
- Properties of crystalline phase
- Grain size
- Intergranular bonding
- Crystal orientation
- Percentage crystallinity - some residual glass pphase impves some properties such as bioactivity- dont want this to be 100%
Give two examples of implantable bone fillers from bovine bone
Endobon
- Osteoconductive Hydroxyapatite ceramic
- Used as a bone graft substitute
- Biological origin
- Used in permanent fillings for trauma surgery and orthopedics
Bio-Oss
- Osseointegrates with newly formed bones
- Is resorbed by adjacent osteoclasts
What is Corraline Hydroxyapatite
Sold as Pro Osteon
Hydrthermically converted marine coral exoskeletons converted into hydroxyapatite
The interconnected porous structure is similar to that of bone- Provides a strong natural foundation for new bone ingrowth and offers strong support
The strength once healed is similar to that of the actual bone
No implant rejected and has no immune response or disease transmission
The healing rates are equivalent to that of the patients own bone
Define Composits
Consisting of two or more chemically distinct constituents in a macro scale having a distinct interface
Define Composits
Consisting of two or more chemically distinct constituents in a macro scale having a distinct interface
What advantages does using a composite have
- Improves mechanical properties like toughness
- Improves degradability
- Can combine strength with cell adhesion properties
- Can be used to allow the release of a drug/growth factor whilst maintain structure
- Higher tensile strengths and moduli that both biological materials and polymers
- They can be designed with crack deflecting abilities though laminations, voids and fibre reinforcements
What materials can be mixed with bioceramic in order to reinforce them
Carbon Fibre Polymer fibres- Kevlar used in dentistry Ceramics Glass fibres PLA and PGA cen self reinforce
Give an example of a commmercially available biomaterial composit
HAPEX
Hydroxyapatite and high density polyethene- the cells attach themselves to the hydroxapatite and grow
Electrospinning Composites
Nanoparticles are dissolved in the same solvent as PCL to make a solution with dispersed particles and then are spun using standard methods
This often requires a compromise between mechanical and biological properties
