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Oral Biology > Components of the Teeth - Enamel > Flashcards

Components of the Teeth - Enamel Flashcards

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1
Q

what does cariogenic mean

A

this is something that creates caries - “cariogenesis” is the creation of caries

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2
Q

how does acid lead to the development of caries

A

it removes certain components of the tooth structure

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3
Q

what is the structure of enamel essential for

A

the development of caries

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4
Q

give a brief summary of the features of enamel

A
  • it is the hardest tissue in the body
  • resists abrasion
  • brittle
  • supported by dentine
  • covers the crown of the tooth
  • varies in thickness
  • translucent
  • transparency of enamel increases with mineralisation
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5
Q

why is enamel the hardest tissue in the body

A

it is often exposed to traumas like biting and chewing that it needs to be resilient for

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6
Q

what is attrition

A

this is the normal wear of a tooth throughout its lifetime.

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7
Q

what is abrasion

A

wear over a very strong activity in which there is a more pathological wear. this includes activities like grinding of teeth, or dents in a tooth where there is constant contact and wear.

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8
Q

how must teeth be restored in older invididuals

A

in such a way that looks natural, including colour and level of wear. designing to make them look like the teeth of a teenager will not look natural on them

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9
Q

explain what is meant by describing enamel as brittle

A

this means it is breakable, where without any support the enamel would break apart from force

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10
Q

why does the enamel not break apart from force if it so brittle

A

it is cushioned by the dentine underneath the surface. if left unsupported when doing a tooth restoration, it would certainly break apart if any force was applied to it

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11
Q

what does it mean to say enamel is translucent

A

the light can pass thrugh it. the colour of tooth is actually due to the dentine underneath, rather than the actual enamel on the top surface.

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12
Q

where do enamel and dentine grow from

A

the amelo dentino junction

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13
Q

what are the cells that produce enamel called

A

ameloblasts

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14
Q

in what structure is enamel produced in

A

rods, or otherwise known as prisms.

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15
Q

what is the thickness of enamel dependent on

A

the function of the tooth

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16
Q

describe the regional variations of enamel

A

the surface enamel is more mineralised and harder than deeper enamel due to long term wear
the hardness of enamel decreases from the cusp tip (posterior teeth) or incisal edge (anterior teeth) to the cervical region
these properties have both functional and clinical significance

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17
Q

give a brief outline of the enamel rods

A

these are the basic units of enamel, and run from the amelo dentino junction to the surface. they contain hydroxyapatite crystallites, and their orientation of these crystallites will vary within and along the rod

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18
Q

what does rod structure arise from in relation to crystallites

A

their orientation

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19
Q

breakdown the different components and their composition within enamel

A
  • hydroxyapatite makes up 95% of the weight of enamel, and about 90% of its volume
  • water makes up 4% of weight and around 5-10% volume
  • the organic matric makes up 1% of the wight and around 1-2% of the volume
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20
Q

what can be found within the organic matrix of enamel

A

proteins, like amelogenins, enamelins, peptides and amino acids

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21
Q

what are the different surface types found on enamel

A

smooth surface
pits and fissures

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22
Q

is surface enamel always different to deeper enamel

A

no, they are exactly the same at the start point of their lifetime but over time changes as the tooth is exposed

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23
Q

what does the hardness of enamel depend on

A

its mineralising and demineralising

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24
Q

what defines crystallites

A

the proteins

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25
Q

when is enamel formed

A

it is made before the tooth erupts in the mouth, by ameloblasts, which die once the tooth erupts.

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26
Q

why does the tooth lose its ability to make enamel

A

the ameloblasts die as soon as the tooth erupts

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27
Q

what is responsible for giving bone much of its hardness

A

hydroxyapatite

28
Q

which protein makes up most of the enamel proteins

A

amelogenins

29
Q

what are the three stages of amelogenesis

A

presecretory, secretory, and maturation.

30
Q

what is dental papilla

A

a condensation of odontoblasts

31
Q

what happens to the translucency of teeth as people age

A

increases

32
Q

what colour is young enamel

A

white

33
Q

what composition of enamel is hydroxyapatite crystals

A

95%

34
Q

describe the structure of the hydroxyapatite crystals in enamel

A

long flat ribbons that are rhomboidal in cross section analysis. some of them can be distorted by crowding during development.

35
Q

are the hydroxyapatite crystals wtihin enamel larger or smaller than in dentine

A

larger

36
Q

why are there incremental lines on enamel

A

due to the phasic way that enamel develops

37
Q

what makes up enamel

A

the enamel rods/prisms. these are a basic structural unit of enamel and are keyhole shaped, and are formed by the hydroxyapatite crystals.

38
Q

how can enamel be described in relation to its composition of cells

A

it lacks cells and is a calfified tissue

39
Q

where is enamel thickest on the tooth

A

the cusp and incisal edge

40
Q

where is enamel thinnest on the tooth

A

the cervical margin

41
Q

why does the thickness of enamel vary depending on the location on the tooth

A

the areas that suffer more attrition has more enamel and will have a reduced risk of fracture

42
Q

how does the hardness and density of enamel change through its depth

A

these features decrease as you go from the surface enamel to the interior, subsurface layer

43
Q

how are incremental lines removed from enamel

A

attrition and abrasion

44
Q

what are the different types of incremental lines

A

straie of retzius and cross striations

45
Q

describe the straie of retzius

A

these are a type of incremental line found on the surface of enamel. they run obliquely along the enamel prisms to the surface, and when they reach the surface they form perikymata

46
Q

describe cross striations

A

these are short period incremental lines on the enamel that are formed parallel to the secretory face of ameloblasts. they cross enamel prisms at right angles

47
Q

what causes the small pits on perikymata

A

the impressions of the ends of ameloblasts

48
Q

how many days does it take for enamel to reach its full thickness

A

625

49
Q

how many crystallites are found within each enamel prism

A

several million

50
Q

how many different patterns of enamel prisms are there

A

three

51
Q

what is type 1 of enamel prisms

A

these form complete prism boundaries

52
Q

what is type 2 and 3 of enamel prisms

A

the prism boundaries are incomplete, and have a keyhole pattern. the tail points cervically

53
Q

give a description of surface enamel

A

this is the most clinically relevent form of enamel as it is susceptible to caries, erosion etc. it is harder, less porous and less soluble than subsurface enamel.

54
Q

when does enamel restrict fracture the most effectively

A

in regions where prisms make an acute angle with the surface

55
Q

give a description of the pores found within enamel

A

the pores are waterfilled spaces that are found between the crystallites.

56
Q

where are the enamel pores that are accessible for larger molecules located

A

prism boundaries

57
Q

what are some features that extend from the dentine into the enamel at the amelodentine junction

A

enamel spindles, tufts and lamellae

58
Q

what are enamel lamellae

A

features that are hypomineralised and extend from the junction to the surface of the enamel.

59
Q

what are enamel spindles

A

narrow tubules

60
Q

what are enamel tufts

A

these are features that resemble tufts of grass, and they contain tuftelin

61
Q

which area of enamel is more soluble

A

the core is more soluble than the periphery of enamel

62
Q

what determines the strength and resistance to fracture of enamel

A

arrangement of crystallites and prisms

63
Q

when is the effect of fluoride on enamel strength and remineralisation most effective

A

when it has replaced 50% of the hydroxyl groups

64
Q

are there prisms on the narrow surface zone of enamel

A

no

65
Q

presecretory stage of amelogenesis

A
  • inner enamel epithelial cells differentiate to form ameloblasts by stretching and becoming tall columnar cells
66
Q

secretory stage of amelogenesis

A

ameloblasts secrete organic matrix to form the full enamel thickness

67
Q

maturation stage of amelogenesis

A

ameloblasts carry out activities that help with degradation of enamel matrix and replacement by minerals or inorganic material

Oral Biology (27 decks)

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