Biomaterial properties of tooth substrate Flashcards
1
Q
Describe ‘Enamel’
A
- 96% Hydroxyapatite
- Most mineralized tissue in body
- Hardest tissue in body
- Rods/interrods
- Rod sheath
2
Q
Describe ‘Enamel viscoelasticity’
A
- Enamel is much tougher than pure hydroxyapatite
- Enamel protein bonds between crystals break when force is applied.
- Crystals can move with respect to other crystals.
- When force removed, crystal can spring back and protein bonds reformed.
3
Q
Describe ‘enamel toughness’
A
- enamel structure guides crack between rods
- Rod direction changes prevent crack propagation
- Ligaments bridge crack and reduces stress concentration.
- Interrod proteins increase toughness.
4
Q
Describe ‘Dentine’ composition
A
- 50% hydroxyapatite
- 25% collagen
- 25% fluids
- 5% other proteins
5
Q
Describe dentine structure
A
- Dentinal tubules radiate from pulp to DEJ
- Two dentine types: Intertubular and peritubular dentine
6
Q
Describe toughness of dentine
A
- Orientation of collagen prevent cracks
- Dentine is tougher than enamel
- Water acts as plasticizer:
1) hydration increase toughness and ductility
2) Water swells dentine to resist compression
3) Hydrated dentine has reduced hardness and elastic modulus. - Dentine tubules
7
Q
List reasons for high toughness of dentine
A
- Uncracked bridges in interbuluar dentine
- Crack deflection in peritubular dentine
- Microcracking with tubules
- Cracks follow path of the tubules
8
Q
Describe ‘uncracked bridges in intertubular dentine’
A
- These are called loading bridges.
- These bridges can withstand more stress and stop propagation of the crack.
- Occurs due to the orientation of collagen.
9
Q
Describe ‘crack deflection in peritubular dentine’
A
- Higher mineralised and stiffer peritubular dentine.
- Stops the main crack from propagating as energy is dissipated within the tubule.
- Like fillers in resin composites.
10
Q
Describe ‘microcracking with tubules’
A
- Crack breaks in several smaller cracks, which dissipates the force.
- Lowers stress concentration.
11
Q
Describe ‘cracks follow path of the tubules’
A
- Guides crack propagation so the above mechanisms can act.
- Energy is lost at each tubule.
