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Oral Biology > QUIZ 2 Enamel I > Flashcards

QUIZ 2 Enamel I Flashcards

1
Q

mature enamel is ___ in orgin, and is a product of the ___

A
  • ectodermal
  • enamel organ
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2
Q

enamel is brittle, so underlying ___ support is critical for function

A

dentin

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3
Q

can enamel be both demineralized and remineralized?

A

yes

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4
Q

is mature enamel cellular or acellular?

A

acellular

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5
Q

is enamel vital or nonvital?

A

nonvital

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6
Q

is there vasculature associated with mature enamel?

A

no

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7
Q

enamel is the hardest tissue in the body. in other words, it is the most ___

A

mineralized

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8
Q

describe the color of mature enamel

A

it is translucent, with a range of colors

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9
Q

mature enamel covers the ___ of the tooth

A

crown

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10
Q

mature enamel is thicker at the ___, around 2.5mm, and relatively thin at ___

A
  • crown
  • cervical line
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11
Q

mature enamel is composed primarily of what?

A

hydroxyapatite crystals

small but essential protein component: organization of crystals

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12
Q

describe the components of mature enamel by weight

A
  • 96% inorganic material (hydroxyapatite)
  • 1% organic material
  • 3% water
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13
Q

describe the components of mature enamel by volume

A
  • 85% inorganic (hydroxyapatite)
  • 3% organic
  • 12% water
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14
Q

describe the organic component of enamel

A
  • 1-2% distributed between hydroxyapatite crystals
  • no collagen
  • enamel proteins, some present only in developing enamel
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15
Q

what are the major enamel proteins in the organic component of enamel?

A

amelogenins, ameloblastins, enamelin, tuftelin

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16
Q

describe enamel crystals

A
  • form the organization of enamel
  • closely packed, long, ribbon-like
  • many crystals packed together form both the enamel rods and the interrod enamel
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17
Q

the mineral component of enamel is hydroxyapatite, but lots of enamel crystals are actually composed of ___

A

carbonatoapatite (carbonated apatite)

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18
Q

what is the formula for hydroxyapatite?

A

Ca5(PO4)3(OH) x2

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19
Q

how can carbonatoapatite be formed from hydroxyapatite?

A

CO32- can substitute for both PO43- (usually) and OH- (sometimes)

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20
Q

hydroxyapatite can incorporate what 3 things into its structure?

A

carbonate, magnesium (more vulnerable to acid attack), and fluoride (less vulnerable to acid attack)

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21
Q

___ and ___ are incorporated into the more inner enamel, and ___ in the outer enamel

A
  • carbonate and magnesium
  • fluoride
  • thus, outer enamel is said to be more resilient in the face of an acid attack
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22
Q

each enamel crystal is ___ in shape, reflective of the individual ___ unit cell

A
  • hexagonal
  • hydroxyapatite
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23
Q

what are the dimensions of mature enamel crystals?

A

60-70nm wide, 25-30nm thick, and can be very long - may run the entire length of the enamel layer (in the mm range)

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24
Q

___ symmetry increases as crystals mature

A

hexagonal

but fully mature enamel crystals lose their shape somewhat

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25
what is an enamel rod?
cylindrical accumulation of enamel crystals, lined up along the long axis of the rod
26
rods generally run perpendicular to the \_\_\_
DEJ (pulp) they radiate outwards from the center
27
are enamel rods straight?
not completely; they curve somewhat as they progress towards the surface
28
rods are often called prisms. why is this technically incorrect?
rods are not that regular in terms of geometry
29
1 rod = 1 \_\_\_
ameloblast it is important to realize that 1 ameloblast will actually contribute to the surrounding rods as well
30
rods are organized into rows, which run in ___ directions
alternating forms a dense meshwork of cylinders
31
why is the orientation of rods impossible to tell from light microscopy?
rods throw off light in all directions
32
what is the relatively protein-rich area of enamel that surrounds the rods?
rod sheath
33
the rod sheath runs about 3/4 of the way around each rod, for the most part separating ___ and \_\_\_
rod and interrod enamel
34
in the gaps of the rod sheath, ___ are continuous with the interrod enamel, linking the two together
enamel crystals
35
crystal orientation is mainly parallel to the long axis of the rods, except where?
at the gaps in the sheath area - they bend outwards and become continuous with the interrod enamel
36
what are the two main rod sheath proteins?
ameloblastins and amelogenins
37
interrod enamel has the same basic composition as \_\_\_, but just in different enamel crystal orientation
rods
38
essentially, ___ fills the gaps between rods
interrod enamel more accurately, columns embed in interrod enamel
39
caries are thought to penetrate through the ___ areas, thus between rod and interrod enamel
higher protein rod sheath areas
40
the enamel rod head is ___ to the surface of enamel
perpendicular (they point outwards)
41
in histological sections, they are often demineralized in order to cut sections, so the enamel is not there. what is this called?
the enamel space
42
what are the 3 main phases of the ameloblast lifecycle?
1. pre-secretory - mature from pre-ameloblasts to ameloblasts 2. secretory - deposition of enamel 3. maturation - reduction of organic matrix, increase mineralization via ion transport 4th phase...protective phase
43
what cells form the first pre-dentin?
odontoblasts
44
describe ameloblast activation and deposition of enamel
intial deposition is only around 30% mineralized, with a much larger organic component
45
as enamel matures, ___ component is reduced, and ___ increases
* organic component * mineralization
46
describe the deposition of enamel
* ameloblasts deposit organic matrix via secretory vesicles, which exit the cell apically * the basal lamina separating the pre-dentin and ameloblasts is penetrated by cell projections and broken down * enamel is laid down directly in apposition to pre-dentin/mantle dentin * tomes' process (**not tomes' fiber**) forms, projects into the developing enamel, and is the site of secretory activity (gives a picket fence morphology)
47
ameloblasts are bound together by \_\_\_, forming a front of enamel deposition and keeping the efront moving together in sync
junctional complexes (terminal bars)
48
initial enamel in apposition to dentin does not have a ___ arrangement; it is uniform
rod
49
\_\_\_ effectively forms the enamel rod structure
tomes' process
50
describe the orientation of tomes' process
* distal - towards the forming enamel * proximal - towards the stratum intermedium
51
describe how tomes' process forms the enamel rod structure
1. secretion fro different parts of the process forms interrods first, forms a groove, into which rods are formed 2. small gap around 3/4 of the process fills with organic material and forms the rod sheath 3. eventually, tomes' process retracts
52
after enamel rods have been made and tomes' process retracts, the outer rods are ___ and the final (outermost) enamel is formed without \_\_\_
* straighter * rods * thus, tomes' processes = rods
53
after enamel has been laid down, what do the ameloblasts do?
they return to being a squat cell, much like a pre-ameloblast
54
what results in a single layer of reduced enamel epithelium?
* loss of the stellate reticulum and fusion of the OEE and the IEE * apoptosis reduces cell number
55
prior to eruption, what happens to enamel?
it hardens and becomes highly mineralized through the removal of water, organic material, and increased hydroxyapatite crystal diameter
56
what is the rate of the maturation of enamel?
relatively slow - up to 5 years for some permanent teeth
57
roughly 2/3 of ___ is maturation
amelogenesis it is a relatively slow process
58
the maturation of enamel involves the production of a unique basal lamina at the ___ (generally not collagen IV)
external enamel surface
59
disruption of proteins in the unique basal lamina produced during enamel maturation can result in \_\_\_
enamel hypoplasia the basal lamina probably helps regulate movement of fluid/material
60
what is modulation?
* occurs during enamel maturation * the process by which water and proteins are removed
61
fusion of the enamel organ forms \_\_\_
reduced enamel epithelium
62
after maturation of the enamel, the remains of the enamel organ attaches to the tooth until \_\_\_. enamel organ remnants fuse with the \_\_\_, forming a covering over the tooth
* eruption * oral epithelium
63
a canal (through which the tooth erupts) forms in the covering over the tooth formed by the fusion of the enamel organ with the oral epithelium, and this layer goes on to form the \_\_\_
dentogingival junction
64
what is nasmyth's membrane?
* the membrane formed by cells, basal lamina, and debris that remains on the crown initially after eruption * it is actually composed of the primary enamel cuticle and secondary enamel cuticle
65
what is the primary enamel cuticle?
the mineralized coating, which is the last secretory product of the ameloblasts (possibly the basal lamina)
66
what is the secondary enamel cuticle?
aka dental cutlcle; formed from the remains of the reduced enamel epithelium merged with the oral epithelium and is removed due to mechanical forces
67
what are ruffled cells?
* during the maturation of enamel, infiltration and incorporation of calcium ions into crystals occurs during "ruffling" * lowered pH favors mineralization * secretion of proteolytic enzymes * cell spends 80% of its lifetime in the ruffled form
68
what are smooth cells?
* smooth cells allow diffusion out of protein fragments out of enamel, which leak in between cells and laterally defuse through the cell layer * cell spends 20% of its lifetime in this form
69
during the maturation of enamel, fluctuations in the distal membrane of ameloblast layers causes the transition between ___ and ___ cells
ruffled and smooth this transition can go back and forth, from ruffled to smooth and back to ruffled

Oral Biology (19 decks)

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