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DHS2๐ŸŽ > Enamel > Flashcards

Enamel Flashcards

1
Q

โ€ฆโ€ฆโ€ฆโ€ฆโ€ฆโ€ฆโ€ฆ.what is enamel and where is it found

A

enamel is specialized hard tissue that is unique to teeth covering the dentin of crown

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2
Q

where is the enamel the thickest and where does it taper

A

enamel thickest over cusps and incisal edges(2.5mm) and thins toward cervical margin (0.5mm)

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3
Q

why cant enamel repair itself if damaged

A

due to how its avascular ( no blood vessels) and acellular (no cells) so it lacks regenerative ability

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4
Q

is enamel a living tissue

A

no its nonvital and does not respond to injury like other tissue

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5
Q

how is enamel dynamic

A

enamel exchange ions with surrounding environment allowing remineralization and demineralization

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6
Q

what gives enamel its hardness

A

hydroxyapatite crystals make enamel strong and highly resistant to wear

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7
Q

how does ion exchange affect enamel

A

enamel undergoes ion exchange with saliva , changing its mineral composition over time

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8
Q

what happens if demineralization exceed remineralization

A

leads to caries and erosion

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9
Q

how can enamel be remineralized to prevent caries

A
  • fluoride ( but not exceeding the minimum dosage to prevent fluorosis)

-calcium phosphate

  • fluoride foam trays which is a safer way than giving it systematically by water
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10
Q

why is enamel the hardest

A
  • high in % of inorganic which is 96 % and only 4% organic
  • crystal shape of hydroxyapatite very long and very thick crystals
  • arrangement of crystals is packed in rods and interrods
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11
Q

why is enamel hardness important

A

to withstand chewing and grinding forces making enamel highly abrasion resistant

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12
Q

what makes enamel semipermeable

A

enamel has tiny water filled spaces between crystals allowing small molecules and ions to cross

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13
Q

how do hardness and porosity vary across enamel

A

enamel is harder and less porous at external surface and cuspal enamel is harder and denser than cervical enamel

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14
Q

why is enamel brittle

A

enamel lacks collagen so its not flexible , has low shear strength, and is prone to fracture under certain forces

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15
Q

how does enamel thermal property protect the dental pulp

A

low thermal conductivity and expansion protect the pulp from temperature changes

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16
Q

why is enamel translucent and what color does it appear

A

high crystal content make enamel translucent and it appears yellowish due to underlying dentine

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17
Q

how does aging affect enamel

A

becomes more translucent and showing a stronger yellow hue

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18
Q

chemical composition of enamel

A

mineral: 96%
organic material : โ‰ค 1%
water: 2-3%

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19
Q

how does mineral content of enamel compare to dentine and bone

A

enamel has higher proportion of mineral components than dentine and bone making it harder

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20
Q

what is the main mineral in enamel what what is the chemical formula

A

calcium hydroxyapatite
Ca10(PO4)6(OH)2

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21
Q

describe the shape and organization of hydroxyapatite crystals in enamel

A

crystals are long , large , hexagonal , organized into rods ( prisms) and interrod each with different crystal orientation

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22
Q

does enamel contain organic component and if so what is the structure

A

yes , it has fine network of organic material surrounding the crystals and thin layers around rods

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23
Q

name the primary proteins found in enamel

A

amelogenin, enamelin, ameloblastin, tuftelin, dentine sialophosphoprotein

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24
Q

what other types of proteins support enamel formation

A

enzymes and serum proteins

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25
Q

what role do enamel proteins play in tooth development

A

the guide tooth morphogenesis and mediate mineralization and hydroxyapatite crystal formation

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26
Q

how are enamel proteins used in dentistry

A

aid in periodontal regeneration and can stimulate reparative process in enamel and dentine

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27
Q

which cells are responsible for secreting enamel matrix proteins

A

ameloblasts

28
Q

what begins to precipitate in enamel matrix after ameloblasts secrete it

A

hydroxyapatite crystals

29
Q

what role does amelogenin play in enamel mineralization

A

provides an ideal substrate for HA crystal formation in an environment rich in calcium and phosphate

30
Q

how does enamel mineralization different from other tissues in terms of matrix vesicles

A

it doesnโ€™t involve matrix vesicles it occurs directly in protein matrix

31
Q

at what mineral content is enamel secreted

A

enamel secreted as partially calcified tissue with about 30% mineral content and no pre enamel

32
Q

what happens as enamel matures

A

its mineral content will increase to about 96% as more amelogenin and parts of enamelin dissolve into enamel fluid enhancing mineralization

33
Q

whatโ€™s the basic structural unit of enamel

A

enamel rod or prisms

34
Q

enamel rods or prisms extend from where

A

extend from dentine to enamel except near the dentin a thin rodless enamel zone and outermost layer 30-50 micrometer of rodless enamel at enamel surface

35
Q

describe the shape of enamel rods in cross section

A

tightly packed
keyhole shape
arranged in horizontal rows

36
Q

how do enamel rods appear when viewed longitudinally

A

wavy or sinusoidal form

37
Q

what is interrod

A

region around each enamel rod containing crystals orientated differently from those in rod itself

38
Q

how are crystals orientated in head and tail of enamel rod

A

head : crystals are parallel to the rod long axis
tail: they diverge about 65 degrees from long axis

39
Q

why is enamel orientation important in restorative dentistry

A

cuz enamel unsupported by dentin is prone to fracture so understanding the orientation helps avoid weak stuff

40
Q

how do enamel rods differ in permanent teeth near CEJ

A

enamel rod tilt slightly toward root of tooth

41
Q

what influences the length of enamel rods

A

thickness of enamel ( rods vary in length according to thickness)

42
Q

what is the general orientation of enamel rods in relation to enamel surface

A

usually oriented 90 degrees to enamel surface

43
Q

how many crystals does each enamel rod contain

A

each rod contains several million crystals

44
Q

describe enamel complex arrangement of enamel rods within a tooth crown

A

its spiral shaped and contribute to enamel strength and resistance properties

45
Q

what is rod sheath in enamel

A

layer of organic matrix between enamel crystals mostly located at margins of each enamel rods its primarily made of protein called ameloblastin and other proteins

46
Q

how are enamel rods arranged in cuspal/ incisal regions

A

in spiral arrangements ( Gnarled enamel) for added strength with rods twisted or bent in different axis

47
Q

what is enamel lamellae

A

defect in enamel that appear as cracks from surface inward containing high level of organic material and allowing bacteria to enter this will initiate caries

48
Q

what are enamel tufts

A

small dark branched proteins extending from DEJ into 1/5 to 1/10 of enamel thickness marking areas where rod orientation changes

49
Q

what are enamel spindles

A

short dark finger extension from DEJ to enamel and its formed

50
Q

how is enamel spindles formed

A

odontoblast process travel through the DEJ into developing enamel and when enamel mineralization occur these processes get trapped within enamel forming enamel spindles

51
Q

what are striae of retzius

A

dark striations or lines running from DEJ to enamel surface in cuspal direction

52
Q

what do striae retzius indicate about enamel formation

A

each line corresponds to a specific time interval during tooth development, showing when enamel was incrementally added.

53
Q

what happens when newly differentiated ameloblasts are recruited

A

they contribute to the secretion of enamel, leading to the formation of Striae Retzius as enamel is deposited in layers

54
Q

how do striae retzius appear in longitudnal sections

A

dark lines surrounding tip of dentin

55
Q

where are striae retzius most prominent

A

in permanent teeth

56
Q

what can cause variations in striae retzius

A

from normal physiological changes in ameloblast activity or functional interruptions such as neonatal line

57
Q

what is neonatal line

A

darkened line represents the border between enamel matrix before and after birth

58
Q

what forms neonatal line

A

formed due to sudden change in environment after birth leading to metabolic disturbances in ameloblasts

59
Q

in which teeth is neonatal commonly found

A

in all deciduous teeth and 1st permanent molars

60
Q

what are hunter schreger bands

A

they are optical phenomena observed in enamel appearing as alternating dark and light zones

61
Q

location of hunter schreger band

A

seen in longitudinal sections of enamel specifically in inner 2/3 enamel

62
Q

what causes appearance of hunter schreger bands

A

caused by groups of enamel rods with different rod orientations creating banding pattern that can change with light direction

63
Q

how is surface enamel different from subsurface enamel

A

the chemical and physical characteristics are different surface enamel is less soluble, harder and less porous and they have straie retzius , perikymata and aprismatic enamel

64
Q

what is perikymata

A

concentric liner grooves where striae of retzius reach enamel surface

65
Q

where are perikymata found

A

paraellel to CEJ and separated by ridges

66
Q

under which conditions are perikymata present

A

where enamel has not been abraded or eroded such as in cervical areas

67
Q
A

DHS2๐ŸŽ (8 decks)

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