Ceramics And Polymers Flashcards
General benefits of ceramic implant materials
- Inertness in body fluids
- High compressive strength
- High hardness
Problems with ceramics
- Do not bend easily at room temperature
- Susceptible to crack propagation
- Can undergo static fatigue
Describe notch sensitivity
In ductile materials notch tips widen under load and stress risers decrease
In brittle materials fast fracture happens quickly
Why are compressive stresses not considered as big of a problem with notch sensitivity?
Compressive stresses can be supported across cracks without extending flaws
What is the first notable ceramic in our notes?
Aluminium oxide - Alumina - Al2O3
What is the moh’s hardness grade for aluminium oxide
9
What is the main use of Aluminium Oxide in implants
Hip ball construction (occasionally socket - acetabular cup)
What happens during sintering?
Firing a powder pressed piece, but not melting it, to reduce pore size
What is the second notable ceramic in our notes?
Calcium Phosphate
What is the main use of Calcium phosphate?
Artificial Bone
How is Calcium Phosphate obtained?
Processing sea coral or synthetic production
What three factors affect the type of Calcium Phosphate ceramic that is produced?
Ca/P ratio
Presence of water
Impurities
What is the form of Calcium Phosphate ceramic most closely related to bones and teeth?
Hydroxyapatite
What kind of Calcium Phosphate would be more suitable for bone scaffolds?
Porous Calcium Phosphate
How can Coralline (mostly Calcium Carbonate) be converted to Hydroxyapatite?
React with Ammonium phosphate under heat and pressure
List the three types of polymer molecular structure from weakest to strongest
- Linear
- Branched
- Cross-linked
What are the three classifications of biomedical synthetic polymers
Thermoplastics
Thermosets
Elastomers
Name two Polyolefins
Polypropylene, Polyethylene
What are the three ways that polyethylene is processed
- Low Density (LDPE)
- High Density (HDPE)
- Ultra-High Molecular Weight (UHMWPE)
Two applications for LDPE and HDPE
- Lining of Catheters
- Porous graft (craniofacial augmentation)
Main uses for UHMWPE
- Sliding surfaces in artificial joints with a metal pairing
- High load bearing joints (unbeatable)
Main uses for Polypropylene
- Monofilament suture materials
- Meshes
What is the most important application of polyamides?
Nylon (sutures)
Name three alternative synthetic and non-biodegradable polymers
Poly(Vinyl Chloride) (PVC)
Polyurethanes
Silicone
List three features of Methacrylates e.g. PMMA
Excellent Chemical Resistivity and high bio compatibility
Excellent light transparency
High index of refraction
Hydrogels love____
Water (Hydrophilic)
