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Oral Biology > QUIZ 2 Enamel II > Flashcards

QUIZ 2 Enamel II Flashcards

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1
Q

rods and interrod enamel geometry are directly linked to the geometry of what?

A

the individual ameloblasts

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2
Q

rods are continuous from the ___ to the ___

A

inner enamel to the outer enamel

*uniform enamel at the innermost and outermost; no rods

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3
Q

describe the orientation of rods in relation to one another

A

inner 2/3 is somewhat interwoven, and the outer 1/3 is much straighter

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4
Q

the distal end of tomes’ process directly forms what?

A

1 enamel rod (and surrounding interrod enamel)

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5
Q

___ is formed first, and makes a pit into which the ___ is synthesized

A
  • interrod enamel
  • enamel rod
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6
Q

dentin forms inwards, towards the ___

A

pulp

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7
Q

the ___ deliminates the surface area of the enamel

A

DEJ

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8
Q

enamel is formed ___ as a cap; the dentin is formed ___, making up most of the tooth body

A
  • outwards
  • inwards
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9
Q

is enamel formation simultaneous?

A

no; it forms apically

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10
Q

as the crown grows, there are new ameloblasts that come into play ___

A

cervically

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11
Q

which enamel proteins are responsible for enamel deposition?

A

ameloginins, ameloblastin, enamelin

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12
Q

which enamel proteins are involved in organic component degradation?

A

enamelysin, enamel matrix serine protease (kallikrein 4)

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13
Q

which enamel proteins are involved the basal lamina during maturation?

A

amelotin, odontogenic ameloblast associated protein (ODAM)

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14
Q

which protein is the main protein family in developing enamel (80-90%) and is only expressed while enamel is being produced; it restricts lateral HA crystal growth, preventing crustal fusion. the loss of function of this protein = no enamel rods

A

amelogenins

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15
Q

which protein is around 10% of the enamel organic content, is expressed all the way through to maturation, involves ameloblast adhesion to developing enamel, and its loss of function results is ameloblasts falling off (no enamel)?

A

ameloblastin

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16
Q

which protein is the least abundant (<5%) enamel protein (but largest), is only present at the leading edge of enamel deposition, and whose function is possibly crystal elongation; loss of function = no enamel

A

enamalin

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17
Q

which enamel protein is an MMP (MMP 20), is found during enamel deposition, chops up ameloblastin and enamelin; loss of function results in thin immature enamel, and is critical for the removal of organic component to allow increased mineralization?

A

enamelysin

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18
Q

which enamel protein is secreted during modulation events of enamel maturation, degrades amelogenins, and the loss of function results in immature enamel?

A

enamel matrix serine protease

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19
Q

the basal lamina doesn’t seem to contain much, if any, ___, but instead has a variety of other proteins, including ___ and ___

A
  • collagen IV
  • ODAM and amelotin
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20
Q

describe how enamel acid etching is important clinically

A
  • fissure sealants
  • bonding restorative materials to enamel
  • cementing orthodontic materials to enamel
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21
Q

describe how enamel acid etching provides better bonding surface

A
  • it increases the porosity of enamel surface (infiltration of material into tissue)
  • also removes any debris clinging to the enamel surface
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22
Q

the mechanism of enamel acid etching is similar to ___

A

microbial incursions (acid attack)

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23
Q

enamel acid etching is accomplished by dissolving ___

A

enamel crystals

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24
Q

describe enamel etching

A
  • carbonated apatite in crystal core
    • more prevalent and vulnerable in inner enamel
  • crystal ends are first to dissolve, then along core
  • effectively dissolves from the inside out
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25
Q

etching enamel doesn’t always produce the same effect on the ___

A

surface

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26
Q

what are the 3 possible patterns of acid etching?

A
  • type I - most common
    • preferential removal of rods
  • type II - reverse of type I
    • interrod enamel removed
  • type III - least frequent
    • irregular and indiscriminate pattern
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27
Q

the three possible etching patterns are most likely due to a difference in what?

A
  • the orientation of rod vs interrod enamel crystals - acid etched surface enamel
    • rod crystal ends are perpendicular to enamel surface
    • interrod crystal ends not generally exposed
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28
Q

what is attrition?

A

tooth wear

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29
Q

enamel is non-vital, meaning what?

A

it cannot be replaced (no more ameloblasts)

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30
Q

attrition of enamel may expose ___

A

dentin

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31
Q

in the attrition of enamel, what might be eliminated?

A

topographical features, like pits and fissures

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32
Q

what are the 3 types of attrition?

A

abrasion, abfraction, and erosion

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33
Q

what is abrasion?

A

removal of enamel by abrasive force (ex. aggressive brushing)

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34
Q

what is abfraction?

A

notch-like cervical lesions caused by cyclic loading of teeth which places stress on the interrod-rod interface, causing rods to separate

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35
Q

what is erosion?

A

removal of enamel by break down of crystals (acid)

36
Q

describe how enamel color changes with age

A
  • darkness increases with age
  • thins with age
  • extrinsic staining
37
Q

describe how the nature of the enamel surface layer changes with age

A
  • changes due to ionic exchange from oral environment
  • fluoride ion most prevalent - topical application
38
Q

describe how enamel water content changes with age

A

water content decreases with age as crystals enlarge and decrease pore size

39
Q

describe how enamel brittleness changes with age

A

brittleness increases with age as water is excluded and crystals increase in size

40
Q

describe how enamel permeability changes with age

A

permeability decreases with age, due to increased crystal size and the continued exclusion of water; thus, there is less space between individual crystals

41
Q

describe how changes in emale over time contribute to an overall decreased incidence of caries

A
  • increased fluoride ion content
  • topographical loss of surface areas susceptible to caries (wear of pits and fissures)
  • extrinsic factors like dietary changes
    • less refined carbohydrates consumed by adults
42
Q

describe periodic structural features of enamel

A
  • striae of retzius/perikymata
  • cross striations
43
Q

describe optical structural features of enamel

A
  • hunter-schreger bands
  • gnarled enamel
44
Q

describe histological structural features of enamel

A
  • enamel tufts
  • enamel lamellae
  • enamel spindles
45
Q

___ appear as longitudinal lines or stripes on ground sections (non demineralized) running from the DEJ to the enamel surface

A

striae of retzius

46
Q

striae of retzius may indicate a weekly rhythm in ___

A

enamel deposition (rings on a tree)

47
Q

striae of retzius follow the ___ growth pattern

A

appositional; move from the inside out, just like enamel

48
Q

striae of retzius may be due to the timing of ___ during tooth development; certain cohorts of cells become active at the same time in a ___ way; the striae may delineate these these cohorts

A
  • ameloblast differentiation
  • cervical
49
Q

striae of retzius have increased ___ content

A

organic

50
Q

accentuated striae (darker), such as the neonatal line, indicate what?

A

significant physiological disturbances

51
Q

what is the neonatal line?

A
  • most accentuated stria of retzius
  • reflects physiologic changes occurring during birth
  • found in all primary teeth, sometimes cusps of first permanent molars
52
Q

what is perikymata?

A
  • surface manifestations of striae of retzius visible on the enamel surface
  • shallow furrows where stria intersect surface
53
Q

cross striations run at a right angle to the ___ direction

A

rod; more or less the DEJ

54
Q

enamel growth rate is about 4um/day, which is the distance between ___

A

cross striations; so they are relatively close together

55
Q

cross striations may indicate what?

A

cyclical variations in rod (organic, mineral density)

56
Q

ameloblast differentiation (enamel production) proceeds in what direction?

A

cervically

57
Q

stria of retzius do not run straight; they follow the contour of what?

A

the cohort of ameloblasts

58
Q

striae of retzius appear best in ___ sections

A

longitudinal; depending on how you cut into the tooth, striae will appear in different orientations

59
Q

rods run in ___ directions, toward ___

A
  • all
  • the tooth surface
60
Q

bands of hunter-schreger are visible in ___

A

ground sections

61
Q

___ are an optical phenomenon due to differential light ascattering when adjacent groups of rods alternate direction

A

bands of hunter-schreger

they appear as alternating light/dark bands

62
Q

bands of hunter-schreger represent what?

A

areas of enamel rods cut in cross-section dispersed between areas of rods cut longitudinally

63
Q

bands of hunter-schreger extend 2/3 the distance from the ___ to ___

A

DEJ to surface

the 1/3 of outer enamel generally runs straighter

64
Q

gnarled enamel is visible in ___

A

ground sections

65
Q

gnarled enamel is seen mostly where?

A

around the DEJ under the cusps/incisal area, short distance into enamel

66
Q

how is gnarled enamel formed?

A
  • from a complex twisting of rods as they proceed vertially away from the DEJ
  • twisting of vertically directed rods around a small diameter ring
    • consider that amelogenesis proceeds from the enamel knot/crown towards the cervical region of the tooth
67
Q

what are enamel tufts?

A
  • “tufts of grass” seen in ground sections; look like cracks
  • project from about 1/3 to 1/2 into the enamel, but do not reach the surface
  • developmental feature
68
Q

enamel tufts contain more ___ and are ___

A
  • enamel proteins
  • hypocalcified
69
Q

enamel tufts are a developmental feature perhaps caused by what?

A
  • abrupt changes in enamel rod direction, possibly due to initial crowding of ameloblasts
    • crowding causes some gaps where rods meet, which fill with organic material (protein)
70
Q

structurally, ___ convey on enamel a bit of a “give” to help prevent fractures

A

enamel tufts

71
Q

___ appear as cracks in ground sections which traverse the whole length of the enamel

A

enamel lamellae

72
Q

enamel lamellae contain ___ proteins

A

organic material

73
Q

describe how enamel lamellae are developmental

A

areas where enamel proteins not completely removed or trapped bits of the enamel organ

74
Q

what is the function of enamel lamellae?

A

may function to give the enamel more structural support (like fault lines) to help resist fracture

75
Q

___ are the result of odontoblastic processes that traverse the DEJ and penetrate the enamel

A

enamel spindles

76
Q

enamel spindles proceed a very short distance into ___

A

enamel

77
Q

where do enamel spindles often appear?

A

at incisal and cuspal tips

78
Q

are enamel spindles enamel?

A

no; they may have trace amounts of dentin (collagen) associated with them

79
Q

what is genetic dysplasia?

A

developmental problems with tooth development/enamel formation

80
Q

___ are very susceptible to physiological changes (birth, high fevers, etc), which can result in disruption in ___ for a time

A
  • ameloblasts
  • ameloblast function
81
Q

minor physiologic changes cause structural enamel changes visible only ___

A

histologically

82
Q

severe physiological changes can do what to enamel?

A

death or damage of ameloblasts with easily visible defects

83
Q

what is tetracycline staining?

A
  • tetracycline is incorporated into all mineralizing tissues (enamel, detin, cementum, and bone)
  • brown, yellow, or gray band of pigmentation
  • tooth form is normal; basically only cosmetic
84
Q

the severity of tetracycline staining is proportional to what?

A

dose and duration

85
Q

excess fluoride interferes with ___, resulting in fluorosis or mottled enamel

A

amelogenesis

86
Q

what are common fluoride induced enamel defects?

A
  • fluorosis or mottled enamel
  • hypermineralized enamel
  • chalk white or brown in color
  • can result in pits on teeth
  • tooth form is normal

Oral Biology (19 decks)

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