Enamel Flashcards
What is the hardest tissue in the body?
Enamel
Which tissue supports enamel?
Dentine
What would happen to enamel without dentine to support it?
Enamel would break. It is very brittle and fragile. This is one of the reasons restorative procedures fail.
Enamel is translucent. What does this mean?
Light can pass through it
What determines the colour of enamel?
The colour of the dentine
When does enamel develop?
During the embryo stage
Which structure does enamel develop from?
Oral epithelium
What effect does mineralisation have on the transparency of enamel?
Transparency increases with mineralisation
Which structure is formed first: the crown or the root?
Crown
Which cells form enamel?
- Ameloblasts
- Each ameloblast forms one enamel prism
Which cells produce dentine?
Odontoblasts
Explain how enamel and dentine are formed
Enamel and dentine are produced as matrixes which form a mineralised tissue - they are not produced in their mineralised form
Describe the orientation of enamel rods (prisms)
- Crystallite orientation is determined during enamel formation
- Crystallites are deposited at right angles to ameloblast membrane
Describe the variations in thickness of enamel at different regions of the tooth
- Surface enamel is more mineralised and harder than deeper enamel
- Hardness decreases from cusp tip/incisal edge to cervical region
What is the basic unit of enamel?
Rod/prism
What are the boundaries of enamel rods?
Rods run from the amelo-dentine junction (ADJ) to the surface
What are enamel rods made up of?
Hydroxyapatite (HA) crystallites
Which teeth have thicker enamel: permanent or deciduous teeth?
Permanent teeth
Describe the content of enamel
- Hydroxyapatite (95% of weight, 90% of volume)
- Water (4% weight, 5-10% volume)
- Organic matrix (1% weight, 1-2% volume)
Why is losing water and organic content bad for teeth?
Makes them more fragile
Why can tooth whitening be damaging for teeth?
Requires hydrogen peroxide to penetrate tooth and remove proteins and water. Tooth structure loses its strength.
What is hydroxyapatite made of?
Calcium, phosphate and hydroxyl
What is hydroxyapatite called if fluoride replaces the hydroxyl group?
Fluoroapatite
Stronger than hydroxyapatite
Which organic components are found in enamel?
Proteins: amelogenins, enamelins, peptides, amino acids
Which teeth are fissures common in?
Premolars and molars
