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1 - IOE - Dental Anatomy > Dental Enamel > Flashcards

Dental Enamel Flashcards

1
Q

What does the enamel do

A
  • Forms outer covering of tooth
  • Modifies colour of tooth
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2
Q

Why are younger teeth whiter

A

Less translucent enamel

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3
Q

Where is enamel thickest

A

Over cusps and incisal edges

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4
Q

Where is enamel thinnest

A

At cervical margin

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5
Q

How does enamel thickness evolve with time

A

Thickness declines gradually to become a very thin layer at the cervical margin

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6
Q

What is the composition of enamel

A

Almost pure mineral - hydroxyapatite

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7
Q

What are the physical properties of enamel

A
  • Very hard due to high mineral content & its unique microstructural organisation
  • Withstand forces from mastication
  • High abrasion resistance so it wears down slowly
  • Cannot be repaired or replaced
  • Brittle so it depends on dentine for resilience
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8
Q

What proteins comprise the matrix of immature enamel

A
  • Amelogenin
  • Ameloblastin
  • Enamelin
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9
Q

What are the chemical properties of human enamel

A
  • Hydroxyapatite in enamel forms larger crystalites
  • Crystalites are long, ribbon-like
  • Tightly packed with pores
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10
Q

How are crystallites grouped

A

Grouped as prisms - some form the interprismatic enamel

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11
Q

Where do enamel spindles arise

A

At the ADJ, particularly around the cusps of teeth where most crowding of odontoblasts occurs

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12
Q

What are enamel tufts

A
  • Hypomineralised structures coming from the ADJ
  • Tufts are spaces between prisms that contain the enamel protein ‘tuftelin’
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13
Q

What are enamel lamellae

A
  • Fine cracks in the surface of enamel
  • Extend from surface of enamel to ADJ
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14
Q

When and why are enamel lamellae formed

A
  • During enamel development
  • Due to incomplete maturation of enamel development or stress cracks
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15
Q

Describe the structure of the newly erupted outer enamel

A

Non-prismatic

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16
Q

Why is surface enamel more highly mineralised

A

Absence of prism boundaries

17
Q

Whats the advantage of surface enamel containing more fluoride than subsurface enamel

A
  • Increased density
  • Increased hardness
  • Decreased solubility in comparison to subsurface enamel
18
Q

Whats the advantage of surface enamel being aprismatic

A
  • Not subject to abrasion
  • Less porous
  • Less susceptible to acid dissolution
19
Q

Explain the Perikymata Grooves

A

Fine ridges resulting from the termination of the incremental striae of Retzius on the enamel’s surface

20
Q

Describe the sheets of enamel prisms forming the Hunter-Schreger bands

A
  • Prisms are grouped into sheets of 10-13 layers, following a sinusoidal path
  • Groups of prisms above and below them going in different directions
21
Q

Explain how the optical effect (Hunter-Schreger bands) are formed

A

Periodic changes in the direction of prism sheets

22
Q

Why are Hunter-Schreger bands visible

A

Different bands of prisms transmit light in different directions

23
Q

Whats the advantage of the complex pattern of prisms

A

Makes enamel resistant to a fracture

24
Q

What happens to enamel as age increases

A

Becomes progressively thinner due to tooth surface loss

25
Q

Why does the tooth darken as enamel age increases

A

Enamel becomes thinner + reduced translucency of tooth

26
Q

Why does enamel become less permeable with age

A
  • Microporosity reduces - less spaces between crystallites
  • Crystals acquire more ions
  • Crystals increase in size
27
Q

What dissolves enamel mineral

A

Acids produced by plaque biofilm

28
Q

Where do early lesions develop and where do they progress

A
  • Develop at the surface of enamel
  • Progress through the tissue following the orientation of prisms
29
Q

What does the microporus prismatic structure allow acids to do?

A

Allows acids produced by plaque biofilm to penetrate surface enamel and begin dissolving enamel prisms and crystallites

30
Q

Where will acids penetrate more readily?

A
  • Where there’s greater porosity
  • May tend to progress down paths provided by prism boundaries
31
Q

Why is removal of unsupported enamel an important element in cavity preparation design

A

Caries penetrates to the underlying dentine, leaving overlying enamel unsupported and prone to fracture during mastication

32
Q

What can lead to microleakage

A

Fracture of unsupported enamel

33
Q

What happens to prisms during tooth preparation

A

Prisms are sectioned, cracked and pulled apart

1 - IOE - Dental Anatomy (13 decks)

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