Introduction to Biomaterials Flashcards
Define ‘biomaterial’
Synthetic material used to replace part of a living system or to function in contact with living systems.
Define Cl50
Period of time for the material to fail in 50% of patients.
Describe the types of metals
Metals and alloy: implants (titanium), orthodontic wires, cast restoration (gold alloy), components of partial dentures (cobalt chromium).
Inter-metallic compounds: filling materials (amalgam phases, Ag3Sn).
Advantages and disadvantages of metals
Advantages:
- Favourable mechanical properties
Disadvantages:
- Poor aesthetics
- Undergoes corrosion
- Dense and heavy
Describe ceramics properties and examples
All non-metallic products that are made by burning or firing at high temperature.
Crystalline ceramics: some dental cements (ZnO - zinc oxide, ZnPO4 - zinc phosphate), gypsum products (Calcium sulfate - CaSO4).
Glass ceramics (mixture of amorphous and crystalline structure): porcelain crowns (SIO).
Advantages and disadvantages of ceramics
Advantages:
- Aesthetic quality
- Biocompatibility
- High compressive strength
Disadvantages
- Brittle
- Hard to make
- Expensive
Describe polymers properties and examples
Rigid polymers: denture base polymers (acrylic resin), dental adhesives.
Elastomers: impression materials (polyvinylsiloxane)
Polymer composites: restorative materials (silica + dimethylacrylate), dental cements (Silica + polyacrylic).
Advantages and disadvantages of polymers
Advantages:
- Aesthetic quality
- Easy to manipulate
Disadvantages:
- Prone to hydrolysis
- May degrade with time and temperature
Give examples of intramolecular bonds
- Ionic bonds
- Covalent bonds
- Metallic bonds
Examples of intermolecular bonds
- Hydrogen bonds
- Van der Waals forces
Describe ionic bonds (intramolecular bond)
Atoms are bound together by an electrostatic attraction between positive and negative ions.
An electron donor atom (metallic) transfers one or more valence electrons to an electron acceptor atom (non-metallic).
Properties:
- Poor electrical and heat conductivity.
- Brittle
- Have high melting point.
Describe covalent bonds (intramolecular bonds)
Two or more valence electrons are shared by adjacent atoms (non-metallic).
These atoms have equal tendencies to donate or accept electrons. Properties: - Hard - Poor electrical and heat conductivity. - Brittle.
Describe metallic bonds (intramolecular bonds)
The positive ions (metallic) are immersed in a “cloud” of negative electrons.
The electrons are not exchanged or shared, they have “mobility” in the electron cloud.
Properties:
- good electrical and heat
- conductivity
- Ductile and malleable
- Crystal structure
Describe hydrogen bonds (intermolecular bonds)
Bond between slightly positive hydrogen bound to electron-negative atom and slightly negative electronegative (O, N, F) atom bound to H.
Describe Van der Waals Forces and its different types (intermolecular bonds)
Weak interaction forces between molecules.
London dispersion forces (Induced dipoles):
- small shifts in the electron cloud results in an induced dipole on molecule.
- when the molecule approaches another molecule, it induces a dipole other molecule’s electron cloud.
Keesom force (Permanent dipoles) - Two molecules with permanent dipoles interact with each other.
Debye force (Permanent and induced dipoles) - A permanent dipole induces a dipole on a neighbouring molecule.
