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ORAL HISTOLOGY AND EMBRYOLOGY > ENAMEL > Flashcards

ENAMEL Flashcards

1
Q

the hard, outer
surface layer of
the teeth that
serves to protect
against tooth decay

A

ENAMEL

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2
Q

hardest calcified tissue in the human body

A

ENAMEL

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3
Q

Is the enamel harder or more mineralized at the surface

A

yes

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4
Q

What is the color of the enamel

A

white to grayish-white, slightly yellow appearance only

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5
Q

Is it translucent?

A

yes

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6
Q

Does the enamel provide the shape and contour of the
crowns of teeth

A

yes

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7
Q

Does the enamel act as semipermeable membrane

A

yes

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8
Q

Is enamel a good conductor of both heat and electricity

A

No

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9
Q

Is it vital and capable of regeneration

A

No

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10
Q

Choose which part of the tooth is enamel thickest with 2.0-2.5mm

crest of cusps or incisal edges

fissures and pit facial, lingual
and interproximal surfaces

cervical margin

A

crest of cusps or incisal edges

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11
Q

Choose which part of the tooth is enamel thinner with 1.0 – 1.5 m

crest of cusps or incisal edges

fissures and pit facial, lingual
and interproximal surfaces

cervical margin

A

fissures and pit facial, lingual
and interproximal surfaces

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12
Q

Choose which part of the tooth is enamel thinnest with <100µm

crest of cusps or incisal edges

fissures and pit facial, lingual
and interproximal surfaces

cervical margin

A

cervical margin

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13
Q

What is the inorganic material of enamel?

A

Hydroxyapatite crystals
Varying amount of carbonates
Trace elements (vanadium, manganese, selenium, molybdenum &
strontium)

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14
Q

What is the organic material of enamel?

A

Soluble and insoluble proteins:
Amino acid
Predominantly enamelins

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15
Q

immature enamel

A

AMELOGENNINS

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16
Q

mature enamel

A

ENAMELINS

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17
Q

Basic structural unit of enamel

A

ENAMEL RODS

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18
Q

Enamel rods are first described as

A

hexagonal or prism-like

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19
Q

Enamel rods are more appropriately described as a

A

cylindrical rod

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20
Q

Enamel rod has a pattern of

A

“horseshoe” or
“paddle-shaped” or
“racquet-shaped” with a head and
tail

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21
Q

Number of enamel rods

A

5 – 12 millions

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22
Q

Direction of enamel rods

A

Run in oblique direction and wavy
course

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23
Q

Length of enamel rods

A

greater than the thickness of enamel

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24
Q

Diameter average of enamel rods

A

4 µm

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25
Q

Appearance of enamel rods

A

clear crystalline
appearance

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26
Q

Cross-section of enamel rods

A

hexagonal, round, oval, or fish
scales

27
Q

Submicroscopic Structure Of Enamel Rods

Shape?

A

Keyhole or paddle-shaped.

28
Q

Submicroscopic Structure Of Enamel Rods

Separated by?

A

interrod substance

29
Q

Enamel rods in breadth?

30
Q

Enamel rods in length?

31
Q

Bodies of enamel rods located

A

near the occlusal or incisal
surface

32
Q

Tails of enamel rods point direction

A

cervically

33
Q
  • the rod’s surface
  • contain more enamel
    protein or organic matrix
    and recystallized
    hydroxyapatite crystals
  • more acid-resistant
    than other regions
A

ENAMEL ROD SHEATH

34
Q
  • cements the rods
    together
  • More calcified than the
    rod sheath
  • Less calcified than the
    rod itself
A

INTERROD ENAMEL

35
Q

Direction of enamel rods in general

A

perpendicular to the surface or the dentin

36
Q

Direction of enamel rods near the cusp tip

A

nearly vertical

37
Q

Direction of enamel rods under pits and fissures

A

tent-like manner

38
Q

Direction of enamel rods on proximal or sides

A

nearly horizontal

39
Q

Direction of enamel rods cusp or incisal

40
Q

Direction of enamel rods cervical

A

mainly horizontal or obliquely inclined

41
Q
  • Rods appear twisted around
    each other in a seemingly
    complex arrangement
  • offers the greatest resistance
    to the cusp and incisal areas
    where most of the forces are
    applied
A

GNARLED ENAMEL (GNARLED
ENAMEL ROD)

42
Q
  • Are an optical phenomenon produced
    solely by changes in rod direction
  • thought to be functionally adapted
    structures for the prevention of
    enamel cracking during chewing
A

BANDS OF HUNTER-SCHREGER

43
Q

seen most clearly in
longitudinal ground
section viewed by
reflected light

A

Hunter-Schreger Bands

44
Q
  • found in the inner 4/5 of
    the enamel
  • appear as dark and light
    alternating zones
A

Hunter-Schreger Bands

45
Q

*dark lines crossing the rods
* indicate a daily (or circadian) variation in
the secretory activity of the ameloblasts
* periodic bands or cross striations
* 4 micrometer
* SEM reveals alternating constrictions and
decreasing expansions of the rods

A

TRANSVERSE STRIATION

46
Q

o growth lines
o brownish bands in ground section
o Reflects variation in structure and
mineralization
o etiology:
* Periodic bending of enamel rods
* Variation in organic structure
* Physiologic calcification rhythm - weekly
(or circasepttimanian)

A

INCREMENTAL LINES (STRIAE) OF
RETZIUS

47
Q

Does the increment lines of retzius reach the outer enamel surface?

48
Q

What shape does the incremental lines of retzius form?

A

horse-shoe shaped

49
Q

Is the increment lines of retzius prominent in human permanent teeth

50
Q

When is the increment lines of retzius rare?

A

prenatal enamel

51
Q

In cross section, the lines of retzius appears as __________

A

Concentric rings

52
Q
  • These grooves represent the lines of Retzius
    as they meet the surface enamel
A

Perikymata/Imbrication lines of Pickerill

53
Q

a pattern of line recognizable to the unaided
eye on enamel surface of sound, freshly
erupted tooth

A

Perikymata/Imbrication lines of Pickerill

54
Q
  • shingle-like overlapping arrangement
  • closely spaced - cervical margin
  • further apart - mid-coronal region
  • absent - cusp tips and incisal edges
A

Perikymata/Imbrication lines of Pickerill

55
Q
  • an accentuated line –
    brownish line
  • reflects the
    marked physiologic changes occurring at birth
  • most primary teeth and permanent
    central incisors have these
A

neonatal line

56
Q

▪Originate at the dentinoenamel junction
▪about 1/5 to 1/3 of the
thickness of the entire enamel
▪They resemble tufts of grass
growing out of a root
▪Composed of hypomineralized
enamel rods, interrod enamel
and organic material—enamelin

A

ENAMEL TUFTS

57
Q
  • visible cracks on the
    surface of the enamel
  • confused with cracks
    caused by grinding
    (decalcification)
  • represent site of weakness
  • are important as a pathway
    through enamel
  • function as a possible
    avenue for dental caries
A

ENAMEL LAMELLAE

58
Q
  • because enamel is highly
    mineralized, stress from
    breathing cold air or
    drinking cold beverages
    may cause small cracks to
    occur in enamel,
    especially where enamel
    is weakened by
    underlying caries
A

ENAMEL LAMELLAE

59
Q
  • extensions from dentinal
    tubules that penetrate the
    DEJ into the enamel
  • seen as black or dark
    irregular or spiral-shaped
    or club-shaped structures
  • are normally filled with
    dentinal fluid
A

ENAMEL SPINDLE

60
Q
  • their dark appearance is due
    to the presence of air and
    debris resulting from the
    preparation of the section
  • one of the factors that
    cause the hypersensitivity of
    the dentino-enamel junction
A

ENAMEL SPINDLE

61
Q
  • scalloped junctionthe concavities
    toward dentin
A

Dentino-Enamel
Junction

62
Q

Begin after a few micrometer
of dentin have been deposited

A

AMELOGENESIS

63
Q

Environmental Influences of Amelogenesis

A
  • Nutrition
  • Calcium, phosphorus, protein, fluoride etc…
  • Hypoxia
  • Hyperthermia
  • Infection
  • Physical Determinants
64
Q

Functional Stages of Amelogenesis

A
  1. Morphogenetic Stage
  2. Organization & Differentiation
  3. Secretory Stage – synthesis of enamel
  4. Maturation Stage
  5. Protective Stage

ORAL HISTOLOGY AND EMBRYOLOGY (4 decks)

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