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DHS2🎐 > Enamel > Flashcards

Enamel Flashcards

(67 cards)

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1
Q

………………….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 : ≤ 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 ( enamel matrix) 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
what role do enamel proteins play in tooth development
they guide tooth morphogenesis and mediate mineralization and hydroxyapatite crystal formation
26
how are enamel proteins used in dentistry
aid in periodontal regeneration and can stimulate reparative process in dentine
27
which cells are responsible for secreting enamel matrix proteins
ameloblasts
28
what begins to precipitate in enamel matrix after ameloblasts secrete it
hydroxyapatite crystals
29
what role does amelogenin play in enamel mineralization
provides an ideal substrate for HA crystal formation in an environment rich in calcium and phosphate
30
how does enamel mineralization different from other tissues in terms of matrix vesicles
it doesn't involve matrix vesicles it occurs directly in protein matrix
31
at what mineral content is enamel secreted
enamel secreted as partially calcified tissue with about 30% mineral content and no pre enamel
32
what happens as enamel matures
its mineral content will increase to about 96% as more amelogenin and parts of enamelin dissolve into enamel fluid enhancing mineralization
33
what's the basic structural unit of enamel
enamel rod or prisms
34
enamel rods or prisms extend from where
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
describe the shape of enamel rods in cross section
tightly packed keyhole shape arranged in horizontal rows
36
how do enamel rods appear when viewed longitudinally
wavy or sinusoidal form
37
what is interrod
region around each enamel rod containing crystals orientated differently from those in rod itself
38
how are crystals orientated in head and tail of enamel rod
head : crystals are parallel to the rod long axis tail: they diverge about 65 degrees from long axis
39
why is enamel orientation important in restorative dentistry
cuz enamel unsupported by dentin is prone to fracture so understanding the orientation helps avoid weak stuff
40
how do enamel rods differ in permanent teeth near CEJ
enamel rod tilt slightly toward root of tooth
41
what influences the length of enamel rods
thickness of enamel ( rods vary in length according to thickness)
42
what is the general orientation of enamel rods in relation to enamel surface
usually oriented 90 degrees to enamel surface
43
how many crystals does each enamel rod contain
each rod contains several million crystals
44
describe enamel complex arrangement of enamel rods within a tooth crown
its spiral shaped and contribute to enamel strength and resistance properties
45
what is rod sheath in enamel
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
how are enamel rods arranged in cuspal/ incisal regions
in spiral arrangements ( Gnarled enamel) for added strength with rods twisted or bent in different axis
47
what is enamel lamellae
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
what are enamel tufts
small dark branched proteins extending from DEJ into 1/5 to 1/10 of enamel thickness marking areas where rod orientation changes
49
what are enamel spindles
short dark finger extension from DEJ to enamel
50
how is enamel spindles formed
odontoblast process travel through the DEJ into developing enamel and when enamel mineralization occur these processes get trapped within enamel forming enamel spindles
51
what are striae of retzius
dark striations or lines running from DEJ to enamel surface in cuspal direction
52
what do striae retzius indicate about enamel formation
each line corresponds to a specific time interval during tooth development, showing when enamel was incrementally added.
53
what happens when newly differentiated ameloblasts are recruited
they contribute to the secretion of enamel, leading to the formation of Striae Retzius as enamel is deposited in layers
54
how do striae retzius appear in longitudnal sections
dark lines surrounding tip of dentin
55
where are striae retzius most prominent
in permanent teeth
56
what can cause variations in striae retzius
from normal physiological changes in ameloblast activity or functional interruptions such as neonatal line
57
what is neonatal line
darkened line represents the border between enamel matrix before and after birth
58
what forms neonatal line
formed due to sudden change in environment after birth leading to metabolic disturbances in ameloblasts
59
in which teeth is neonatal commonly found
in all deciduous teeth and 1st permanent molars
60
what are hunter schreger bands
they are optical phenomena observed in enamel appearing as alternating dark and light zones
61
location of hunter schreger band
seen in longitudinal sections of enamel specifically in inner 2/3 enamel
62
what causes appearance of hunter schreger bands
caused by groups of enamel rods with different rod orientations creating banding pattern that can change with light direction
63
how is surface enamel different from subsurface enamel
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
what is perikymata
concentric liner grooves where striae of retzius reach enamel surface
65
where are perikymata found
paraellel to CEJ and separated by ridges
66
under which conditions are perikymata present
where enamel has not been abraded or eroded such as in cervical areas
67

DHS2🎐 (13 decks)

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