ICP L12: Enamel structure and biochemical properties Flashcards
What are the clinical implications of drilling into a tooth
This can undermine the remaining intact enamel structure and produce weak points where crack propagation may occur under loading
What is the colour of enamel
It is greyish or bluish white but appears yellow white as it is semi-translucent and reflects the colour of the underlying dentine
What is the thickness of enamel
Incisors = 0 - 2mm Molars = 2.6mm
Outline the macroscopic structural properties of enamel
It is selectively permeable so small amounts of water can permeate through, it has a refractive index on 1.655 and is soluble in acids
Describe the microscopic properties of enamel
- needle-like crystals
- clustered into prisms containing 1000s crystallites
- prisms arranged into larger arrays with inter prismatic enamel between them
Why is dentine important to the structure of enamel
Because enamel itself is brittle so dentine provides support to withstand the forces applied and this minimises crack and fracture formation
Name a genetic abnormality in enamel which increases the risk of crack propagation
Mucopolysaccharidosis type I
What is mucopolysaccharidosis type I and what does it cause
This is a genetic abnormality in enamel where there is defective protein structure meaning that the enamel and dentine is not well developed which causes gap formation
Because the enamel is not bonded well to the dentine, the surface is under stress during mastication which can lead to crack formation at the EDJ which can spread through the enamel
It can also cause the enamel to completely debond
Where is the greatest pressure applied during mastication
The cusp tips are the load bearing areas - where the is less alignment the enamel is prone to wear and acid dissolution
Why is elastic modulus of enamel important
Because this is its ability to bounce back after being subjected to load so the higher the elastic modulus the better the recovery; similarly the lower the elastic modulus, the lower the recovery and so the increased chance of crack propagation
Compare the elastic modulus of cross sectional and surface enamel
Cross-sectional enamel has a lower elastic modulus than surface enamel
What happens to the elastic modulus when a higher road is applied
It is measured to be lower
What is fracture toughness
The ability to resist brittle fracture when a crack is present
How is the enamel structure designed to resist wear
The rod orientation reduces wear by increasing hardness
How is the enamel structure designed to resist fracture
The inter-rod structure holts cracks
