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OCB02 > Enamel > Flashcards

Enamel Flashcards

1
Q

What is enamel designed for?

A

To withstand biting and wearing forces

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2
Q

What is caries?

A

Loss of mineral due to plaque acids

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3
Q

Where is the enamel thickest?

A

Cusps (up to 2.5mm)

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4
Q

Where is the enamel thinnest?

A

Fissures

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5
Q

Where do teeth decay first and why?

A

Fissures

Very deep and tight so hard to brush and thin enamel

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6
Q

Where are mamelons present?

A

Incisal edges

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7
Q

What are the surface features of newly erupted teeth? (4)

A

Mamelons

Perikymata

Tomes’ process pits

Pearls

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8
Q

What are perikymata?

A

Grooves on surface due to lines of Retzius

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9
Q

How small are Tomes’ process pits?

A

<100um

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10
Q

What are pearls?

A

Bumps of enamel found at the cervical part of tooth

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11
Q

What makes up an enamel prism?

A

10,000 hydroxyapatite crystallites

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12
Q

How long are the enamel prisms?

A

4-7um

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13
Q

What shape are the enamel prisms?

A

Horse-shoe shape, open end pointing toward root

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14
Q

What shape are the crystallites and why?

A

Hexagonal

Packing of ameloblasts

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15
Q

Why are there gaps between prisms and what is the function of these?

A

Crystallites do not line up as well at boundaries (discontinuity)

Allows distribution of fluids

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16
Q

Why are the prisms not uniform in diameter all the way along the length?

A

Cross-striations created daily

Helps lock adjacent prisms together

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17
Q

Which parts of the cross-striations appears darker and lighter?

A

Darker - thinner

Lighter - thicker

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18
Q

What are the three types of incremental lines?

A

Cross-striations

Brown striae of Retzius

Neonatal line (special stria of Retzius)

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19
Q

When and why do the brown striae of Retzius form?

A

Every 7-9 days

Rate of secretion slows and ameloblasts slightly change direction

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20
Q

Why are brown striae of Retzius called brown?

A

Appear brown in transmitted light

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21
Q

Where are the brown striae of Retzius most prominent?

A

Cervical third of enamel

22
Q

What is the neonatal line?

A

Most prominent brown stria of Retzius formed at birth

23
Q

Where are perikymata most prominent?

A

Cervical third of enamel surface

24
Q

What tissues are the dentin and enamel derived from?

A

Dentin - mesenchyme

Enamel - epithelium

25
Q

What triggers ameloblast differentiation?

A

Predentin

26
Q

What type of cell secretes enamel matrix?

A

Long ameloblasts

27
Q

What are the two types of enamel matrix protein?

A

Amelogenins

Non-amelogenins/enamelins

28
Q

What part of the ameloblasts secretes enamel matrix?

A

Tomes’ process

29
Q

Briefly describe enamel mineralisation.

A

Occurs within matrix - matrix gets thinner and hydroxyapatite crystallites grow

30
Q

What happens to the ameloblasts after secretion?

A

Mature and shorten

31
Q

What do the shortened ameloblasts do?

A

Remove proteins (mainly amelogenins) so enamel is not too porous

32
Q

What are the functions of the reduced enamel epithelium? (2)

A

Protective layer during eruption

Fuses with oral epithelium to create junctional epithelium (seal)

33
Q

At what point is the enamel fully mineralised?

A

After eruption in mouth

34
Q

What does the saliva contain which is important in enamel mineralisation? (4)

A

Calcium ions

Magnesium ions

Phosphate ions

Carbonate ions

35
Q

How long does an ameloblast secrete for?

A

1 year

36
Q

How long does matrix secretion for a permanent molar take?

A

4-7 years

37
Q

When is acid etch used?

A

Before restorations and composites

38
Q

Why is acid etch used?

A

Opens up enamel structure and removes smear layer

Allows resin to infiltrate and create a strong bond with tooth

39
Q

What is decussation?

A

Sheets of prisms changing angles relative to each other (crossing over)

40
Q

Describe the path which prisms/ameloblasts take from EDJ to surface.

A

Inner third = sinuous

Outer two-thirds = straight

41
Q

Where are the Hunter-Schreger bands?

A

Inner third of enamel

42
Q

What is the function of the Hunter-Schreger bands?

A

Stress-reliever (compressible)

43
Q

What is a tuft?

A

Where ameloblasts cross over each other

44
Q

What are diazones?

A

Prisms cut transversely

45
Q

What are parazones?

A

Prisms cut longitudinally

46
Q

What are the Hunter-Schreger bands?

A

Paired light and dark bands

Optical illusion caused by reflection (parazones) and transmission (diazones) of light

47
Q

What does the enamo-dentin junction look like?

A

Scalloped line

Concave towards pulp

48
Q

What would happen to the enamel if the dentin was compromised and why?

A

Fracture due to loss of support

Enamel is very brittle

49
Q

What are the enamel spindles/spaces?

A

Where odontoblast processes are trapped

50
Q

What are lamellae?

A

Cracks from EDJ to surface containing organic material

OCB02 (19 decks)

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