Ceramic Biomaterials Flashcards
What are ceramics?
- Referring to products obtained through the action of fire upon earthy materials
- can be defined as inorganic, nonmetallic materials
- Crystalline compounds formed between metallic and nonmetallic elements such as aluminum and oxygen (alumina-Al2O3) calcium and oxygen (calcia - CaO) silicon and nitrogen (silicon nitride-Si3N4)
- Crystals containing metallic and non-metallic ions with strong bonds- hence tend to be hard
What are glasses?
Ceramic composition but not crystalline
What are bioactive glasses?
react with solution to form a calcium phosphate layer on their surface
What are the types of bioceramics?
1st generation: bioinert, non-absorbable
2nd generation: biodegradable, bioactive
3rd generation: scaffolds of biologically active molecules
What is the in vivo reactivity of bio-inert bioceramic?
Isolated by a non-adherent fibrous capsule
What are some examples of 1st generation bioceramics?
Alumina, Al1O3
Zirconia: ZrO2
Carbons (mainly pyrolytic and as fibres in composites)
What is the in vivo reactivity of a biodegradable bioceramic?
Dissolves after a specific time
What are some examples of 2nd generation bioceramics?
Calcium phosphates
Calcium sulphate
Calcium phosphates and sulphates (+ZnO, AL2O3, Fe2O3)
Coralline CaCO3
Hydroxyapatite (HA) (pure and substituted)
Hydroxycarbonate apatite (HCA)
Glasses: by melting and sol-gel
Glass ceramics: A/E glass ceramic and Ceravital
What is the in vivo reactivity of a bioactive bioceramic?
Tightly bonded to living tissues
What is the vivo reactivity of stimulating living tissues regeneration?
Stimulating living tissues regeneration
What are some examples of 3rd generations of bioceramics?
Bioglass: in particulate form
Porous bioactive and biodegradable ceramics
Advanced bioceramics: mesoporous materials, organic-inorganic hybrids
What are the application and function of calcium phosphates?
Bulk: bone graft substitutes, cell scaffolds
= replace the bone loss
Coatings: surface coatings on total joint prosthesis
= provide bioactive bonding to bone
What are the applications and functions of glasses?
Bulk: endosseous alveolar ridge maintenance, = space filling and tissue bonding middle ear prosthesis = replacement of part of the ossicular chain orbital floor prosthesis = repair damaged cone supporting eye
Powder:
Fixation or revision arthroplasty
= restore bone after prostheses loss
Filler in periodontal defects
= periodontal disease treatment
Bone graft substitutes and cranial repair
= augmentation after diverse illness and traumas
What are the applications of glass-ceramics?
Bulk: Vertebral prostheses = replace vertebrae removed by surgery Iliac crest prostheses = substitute bone removed for autogenous graft
Coatings:
Fixation of hip prosthesis
= provide bioactive bonding
What are the applications of calcium sulphate?
Bulk and powder:
Bone graft substitutes
= repairing osseous tissues
Why use bioceramics?
Used initially as alternatives to metals in order to increase the ‘biocompatibility’ of implants, bioceramics three basic types:
- relatively bioinert ceramics,
- bioactive (or surface reactive)
- bioresorbable
What are bioinert ceramics?
- Alumina oxide,Al203 most commonly used
- Zirconia, Zr02 also used in hip sockets
- Highly stable, excellent mechanical properties, good biocompatability, little fibrous capsule formation, non-degradeable
- Zirconia tougher, less stiff, less wear but lower Young’s modulus and strength, more difficult to manufacture, costly.
How can you improve the miscrostructure of alumina?
Hot Isostatic Pressed
What is zirconia commonly used for and what are the problems with this?
Orthopaedic prostheses
Femoral heads for hip replacement prostheses
Can fragment inside patient
= Nucleation and growth of monoclinic phase onthe surface of a ZrO2 ceramic exposed to a moist environment
What can be added to zirconia to improve its properties?
- Alumina provides the material’s hardness and wear resistance
- Zirconia and strontium oxide improves fracture toughness
- very small grain size of the alumina matrix gives high strength and high density
What is an example of a bioactive ceramic?
calcium phosphates
- Bone mineral is carbonated hydroxyapatite, a type of calcium phosphate
- Makes sense that calcium phosphates are highly compatible with bone
- Poor mechanical properties but can be used as coatings or in scaffolds
What is bone most up of?
basically hydroxyapatite
- 50-70% mineral (Hydroxyapatite, a crystalline form of Calcium Phosphate)
- 20-40% organic matrix
Collagen (type 1) – 90% of bone protein
Non-collagenous proteins -10% of all protein (Proteoglycans and glycoproteins)
What is the difference between hydroxyapatite and tricalcium phosphate?
Hydroxyapatite = Ca10(PO4)6(OH)2
tricalcium phosphate = Ca3(PO4)2
How are crystal impurities achieved?
Substitutions (ions commonly substituted into the hydroxyapatite lattice)
- Biological apatite is rich in carbonate and low in calcium
- Substitutions increase solubility
