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BDS2 BAMS Oral Biology > Enamel > Flashcards

Enamel Flashcards

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1
Q

what is the function of enamel

A

resists abrasion

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2
Q

what are features of enamel

A

brittle
varies in thickness
translucent
transparency

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3
Q

what does enamel cover

A

tooth crown

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4
Q

what is enamel supported by

A

dentine

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5
Q

what happens if enamel is unsupported

A

will fail

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6
Q

what does translucency of enamel mean

A

it reflects colors and where the colour is a different place in the dentine due to the shape of the dentinal tubules

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7
Q

what does transparency of enamel increase with

A

mineralization

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8
Q

what is enamels thickness based upon

A

its function

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9
Q

why is the enamel on deciduous teeth thinner

A

they spend less time in the mouth

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10
Q

which is more mineralized - surface or deeper enamel

A

surface

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11
Q

when does surface and deeper enamel have the same level of mineralization

A

when it erupts

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12
Q

what is the purpose of a fissure sealant

A

protect the surface while it is still maturing

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13
Q

Where does the hardness of enamel decrease

A

cervical regions

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14
Q

what is hardness of enamel associated with

A

fragility of enamel

receiving attack from caries

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15
Q

what part of the tooth is more prone to recurrent caries

A

cervical

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16
Q

what is the basic unit of enamel

A

enamel rod/prism

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17
Q

what is the dimensions of the enamel rod

A

5 micrometres x 2.5mm (length of enamel)

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18
Q

where does the rod run from

A

ADJ to the surface

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19
Q

what does the rod contain

A

a high concentration of hydroxyapatite crystallites (more than 106)

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20
Q

what is the arrangement of rods

A

key holes

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21
Q

what are cross striations

A

consequence of daily growth of the rod when it was created

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22
Q

what is the daily growth of rods

A

4 micrometers

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23
Q

what is brown transverse striae

A

consequence of the weekly growth of the rods

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24
Q

what surface is more prone to etching

A

side surface of crystallites

25
Q

what is the distinction between head and tail regions caused by

A

ariations in the orientations of the crystallites in different parts of the rod – there is no real space between the rods, this space is just a difference in orientation of the crystallites

26
Q

what is the weight and volume of hydroxyapatite in enamel

A

weight - 95%

volume - 90%

27
Q

what is the weight and volume of water in enamel

A

weight - 4%

volume - 5-10%

28
Q

what is the weight and volume of organic matrix in enamel

A

weight - 1%

volume - 1-2%

29
Q

what does the organic matrix consist of

A

proteins

30
Q

what are the proteins in the organic matrix

A

amelogenins
enamelins
petptides
amino acids

31
Q

what is there an absence of in the organic matrix of enamel

A

collagen

32
Q

what does the minor protein component regulate in enamel

A

nanomechanical properties of enamel
ts ability to withstand forces is linked to the presence of the organic component and if you remove the organic component you lose the little amount of flexibility that is present

33
Q

when is crystallite orientation determined

A

during enamel formation

34
Q

how are crystallites deposited in regards to the ameloblast membrane

A

at right angles

35
Q

what will the arrangement of the tomes process determine

A

orientation of the crystallites

36
Q

what happens in the development of crystallites

A

Ameloblasts will create a globular structure in which the inner portion can be hyperconcentrated in terms of calcium-phosphate, this is called supersaturation

There is a cocoon protecting the calcium phosphate that needs to be removed for the crystal to form

We require the breakdown of amelogenins - this is the maturation stage of amelogenesis
If we don’t have the breakdown of amelogins then we get amelogenesis imperfecta

The crystal then grows to its full potential

37
Q

what is the formula for hydroxyapatite crystals

A

Ca10(PO4)6(OH)2

38
Q

what is the shape of hydroxyapatite crystals

A

hexagonal

39
Q

how do the crystallites in enamel compare to those elsewhere

A

they are larger

40
Q

what can we have ionic substitution by

A

magnesium
carboante
fluoride

41
Q

what does magnesium substitute

A

calcium

42
Q

what does carbonate substitute

A

phosphate

43
Q

what does fluoride substitute

A

hydroxyl

44
Q

what do we require for substitution

A

remineralization/demineralization process

45
Q

what are ground sections

A

mineral present but no soft tissues

46
Q

what are decalcified sections

A

no mineral but only soft tissues

47
Q

how do enamel rods run

A

sinusoidal course

48
Q

what does periodic orientation cause

A

banding pattern

hunter-schreger bands

49
Q

where are hunter schrager bands absent

A

in outer enamel

50
Q

where do we see gnarled enamel

A

cusps

51
Q

what is gnarled enamel due to

A

greater concentration of rods

52
Q

why do we have gnarled enamel in cusps

A

the greater number of rods means that the distribution of force will be better if we have more rods

53
Q

what are the incremental lines

A

Brown striae of retzius
perikymata
neonatal line

54
Q

what is perkymata

A

exposed on the outside of enamel, disappear and wear off as we

55
Q

what is neonatal line associated with

A

associated with diet change that happens at birth

56
Q

what are enamel tufts due to

A

hypomineralised regions due to the residual matrix protein at prism boundaries. The tufts penetrate the prisms but do not go all the way through

57
Q

what is enamel lamella

A

incomplete maturation of groups of prisms – ‘fault’ line extending through enamel thickness – it goes all the way through the rod

58
Q

what is enamel spindle

A

odontoblast processes extending into enamel. Very early stage of formation of the ADJ, the odontoblast left its projection and created a spindle.

BDS2 BAMS Oral Biology (10 decks)

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