Enamel Flashcards

(58 cards)

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
what is the distinction between head and tail regions caused by
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
what is the weight and volume of hydroxyapatite in enamel
weight - 95% | volume - 90%
27
what is the weight and volume of water in enamel
weight - 4% | volume - 5-10%
28
what is the weight and volume of organic matrix in enamel
weight - 1% | volume - 1-2%
29
what does the organic matrix consist of
proteins
30
what are the proteins in the organic matrix
amelogenins enamelins petptides amino acids
31
what is there an absence of in the organic matrix of enamel
collagen
32
what does the minor protein component regulate in enamel
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
when is crystallite orientation determined
during enamel formation
34
how are crystallites deposited in regards to the ameloblast membrane
at right angles
35
what will the arrangement of the tomes process determine
orientation of the crystallites
36
what happens in the development of crystallites
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
what is the formula for hydroxyapatite crystals
Ca10(PO4)6(OH)2
38
what is the shape of hydroxyapatite crystals
hexagonal
39
how do the crystallites in enamel compare to those elsewhere
they are larger
40
what can we have ionic substitution by
magnesium carboante fluoride
41
what does magnesium substitute
calcium
42
what does carbonate substitute
phosphate
43
what does fluoride substitute
hydroxyl
44
what do we require for substitution
remineralization/demineralization process
45
what are ground sections
mineral present but no soft tissues
46
what are decalcified sections
no mineral but only soft tissues
47
how do enamel rods run
sinusoidal course
48
what does periodic orientation cause
banding pattern | hunter-schreger bands
49
where are hunter schrager bands absent
in outer enamel
50
where do we see gnarled enamel
cusps
51
what is gnarled enamel due to
greater concentration of rods
52
why do we have gnarled enamel in cusps
the greater number of rods means that the distribution of force will be better if we have more rods
53
what are the incremental lines
Brown striae of retzius perikymata neonatal line
54
what is perkymata
exposed on the outside of enamel, disappear and wear off as we
55
what is neonatal line associated with
associated with diet change that happens at birth
56
what are enamel tufts due to
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
what is enamel lamella
incomplete maturation of groups of prisms – ‘fault’ line extending through enamel thickness – it goes all the way through the rod
58
what is enamel spindle
odontoblast processes extending into enamel. Very early stage of formation of the ADJ, the odontoblast left its projection and created a spindle.