Enamel

Question 1

what is the function of enamel

Answer 1

resists abrasion

Question 2

what are features of enamel

Answer 2

brittle
varies in thickness
translucent
transparency

Question 3

what does enamel cover

Answer 3

tooth crown

Question 4

what is enamel supported by

Answer 4

dentine

Question 5

what happens if enamel is unsupported

Answer 5

will fail

Question 6

what does translucency of enamel mean

Answer 6

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

Question 7

what does transparency of enamel increase with

Answer 7

mineralization

Question 8

what is enamels thickness based upon

Answer 8

its function

Question 9

why is the enamel on deciduous teeth thinner

Answer 9

they spend less time in the mouth

Question 10

which is more mineralized - surface or deeper enamel

Answer 10

surface

Question 11

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

Answer 11

when it erupts

Question 12

what is the purpose of a fissure sealant

Answer 12

protect the surface while it is still maturing

Question 13

Where does the hardness of enamel decrease

Answer 13

cervical regions

Question 14

what is hardness of enamel associated with

Answer 14

fragility of enamel

receiving attack from caries

Question 15

what part of the tooth is more prone to recurrent caries

Answer 15

cervical

Question 16

what is the basic unit of enamel

Answer 16

enamel rod/prism

Question 17

what is the dimensions of the enamel rod

Answer 17

5 micrometres x 2.5mm (length of enamel)

Question 18

where does the rod run from

Answer 18

ADJ to the surface

Question 19

what does the rod contain

Answer 19

a high concentration of hydroxyapatite crystallites (more than 106)

Question 20

what is the arrangement of rods

Answer 20

key holes

Question 21

what are cross striations

Answer 21

consequence of daily growth of the rod when it was created

Question 22

what is the daily growth of rods

Answer 22

4 micrometers

Question 23

what is brown transverse striae

Answer 23

consequence of the weekly growth of the rods

Question 24

what surface is more prone to etching

Answer 24

side surface of crystallites

Question 25

what is the distinction between head and tail regions caused by

Answer 25

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

Question 26

what is the weight and volume of hydroxyapatite in enamel

Answer 26

weight - 95% | volume - 90%

Question 27

what is the weight and volume of water in enamel

Answer 27

weight - 4% | volume - 5-10%

Question 28

what is the weight and volume of organic matrix in enamel

Answer 28

weight - 1% | volume - 1-2%

Question 29

what does the organic matrix consist of

Answer 29

proteins

Question 30

what are the proteins in the organic matrix

Answer 30

amelogenins enamelins petptides amino acids

Question 31

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

Answer 31

collagen

Question 32

what does the minor protein component regulate in enamel

Answer 32

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

Question 33

when is crystallite orientation determined

Answer 33

during enamel formation

Question 34

how are crystallites deposited in regards to the ameloblast membrane

Answer 34

at right angles

Question 35

what will the arrangement of the tomes process determine

Answer 35

orientation of the crystallites

Question 36

what happens in the development of crystallites

Answer 36

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

Question 37

what is the formula for hydroxyapatite crystals

Answer 37

Ca10(PO4)6(OH)2

Question 38

what is the shape of hydroxyapatite crystals

Answer 38

hexagonal

Question 39

how do the crystallites in enamel compare to those elsewhere

Answer 39

they are larger

Question 40

what can we have ionic substitution by

Answer 40

magnesium carboante fluoride

Question 41

what does magnesium substitute

Answer 41

calcium

Question 42

what does carbonate substitute

Answer 42

phosphate

Question 43

what does fluoride substitute

Answer 43

hydroxyl

Question 44

what do we require for substitution

Answer 44

remineralization/demineralization process

Question 45

what are ground sections

Answer 45

mineral present but no soft tissues

Question 46

what are decalcified sections

Answer 46

no mineral but only soft tissues

Question 47

how do enamel rods run

Answer 47

sinusoidal course

Question 48

what does periodic orientation cause

Answer 48

banding pattern | hunter-schreger bands

Question 49

where are hunter schrager bands absent

Answer 49

in outer enamel

Question 50

where do we see gnarled enamel

Answer 50

cusps

Question 51

what is gnarled enamel due to

Answer 51

greater concentration of rods

Question 52

why do we have gnarled enamel in cusps

Answer 52

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

Question 53

what are the incremental lines

Answer 53

Brown striae of retzius perikymata neonatal line

Question 54

what is perkymata

Answer 54

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

Question 55

what is neonatal line associated with

Answer 55

associated with diet change that happens at birth

Question 56

what are enamel tufts due to

Answer 56

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

Question 57

what is enamel lamella

Answer 57

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

Question 58

what is enamel spindle

Answer 58

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