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2 - Oral Biology (Head And Neck Anatomy) > Enamel > Flashcards

Enamel Flashcards

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1
Q

What are features of enamel?

A

Hardest tissue in body
Resists abrasion
Brittle
Supported by dentine
Covers tooth crown
Varies in thickness
Translucent
Transparency increases with mineralisation

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2
Q

Where is enamel thicker?

A

Insical edge is thicker
Molar cusps are thicker

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3
Q

What are the enamel regional variations?

A

Surface enamel more mineralised and harder than deeper enamel
Hardness is more at cusp/incisal edge

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4
Q

What is the basic unit of enamel?

A

Enamel rod/prism

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5
Q

What are the qualities of the rods?

A

Rod is 5micrometres times 2.5 millimetres
Run from ADJ to surface
Contain >10^6 HA crystallites
Light microscopy appearance is due to the orientation of crystallites
Orientation varies along and within the rod

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6
Q

What are crystallites that run parallel to the rods called?

A

Rod regions

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7
Q

What are crystallites that run inclined to the rods called?

A

Inter-rod regions

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8
Q

Where is acid-etch more effective?

A

Within inter-rod regions because the etch works better on the sides of the crystallites

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9
Q

What are the cross-stations found in long parallel rods due to?

A

Due to daily incremental growth of enamel

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10
Q

What are the brown transverse striae due to?

A

Formed due to weekly growth

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11
Q

What is the shape of enamel rods, end on?

A

Keyhole

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12
Q

What is between the rods?

A

Inter-rod regions

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13
Q

In the keyhole shape, why is there a ‘head’ and a ‘tail’?

A

Both composed of the same hydroxyapatite crystals however the distinction is caused by variations of the crystallites in difference parts of the rod

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14
Q

What is the content of enamel?

A

Hydroxyapatite - 95% (weight), 90% (volume)
Water - 4% (weight), 5-10% (volume)
Organic matrix - 1% (weight), 1-2% (volume)

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15
Q

What is the organic matrix made of?

A

Proteins - amelogenins, enamelins, peptides, amino acids

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16
Q

What does the protein content of the rods regulate?

A

The nano mechanical properties of enamel (flexibility)

17
Q

Why is tooth whitening harmful?

A

Removes protein component therefore making enamel more fragile

18
Q

When is crystallite orientation determined?

A

During enamel formation

19
Q

How are crystallites deposited?

A

At right angles to ameloblast membranes

20
Q

What process is responsible for the organisation?

A

Tomes process (landmark within ameloblast)

21
Q

Describe the process of crystallite formation

A

Proteins secreted by ameloblasts form pellets which concentrate calcium and phosphate in an organised way

Protein is then removed for crystallite to grow on it’s own

22
Q

What are the qualities of hydroxyapatite crystallites?

A

Made of hydroxide, phosphate, calcium
Hexagonal shape
In enamel, larger than in dentine, cementum or bone

23
Q

What can you substitute for hydroxide?

A

Mg2+, CO3, F-

24
Q

What is important to note when looking at histological samples of enamel?

A

Hard tissues are difficult to cut
-ground sections have the mineral present (however no soft tissues)
-decalcified sections have no mineral present (only soft tissue)

25
Q

What course do enamel rods run?

A

A sinusoidal course

26
Q

What are some enamel optical features, and properties of them?

A

Hunter-Schreger bands - changes in direction between adjacent groups of rods, absent in outer enamel
Gnarled enamel -found in cusps, concentrated rods that look intertwined
Brown striae of retzius- (incremental lines), weekly enamel growth
Perikymata -once tooth erupts, surface, lines wear off
Neonatal line - seperates enamel formed after birth/before birth

27
Q

What are features found in the ADJ and what are their properties?

A

Enamel tufts -hypomineralised regions due to residual matrix protein at prism boundaries (incomplete maturation)

Enamel lamella/fault line -incomplete maturation of groups of immature prisms extending through enamel thickness

Enamel spindles -odontoblast processes extending into enamel

28
Q

Where can caries occur?

A

Fissures

2 - Oral Biology (Head And Neck Anatomy) (13 decks)

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