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Oral Histology Exam 1 > Enamel Tissue > Flashcards

Enamel Tissue Flashcards

1
Q

what is the hardest one of the 4 mineralized tissues of the body?

A

enamel

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2
Q

True or false: enamel is only one that is not a connective tissue.

A

true

its an ectodermal derived tissue (formed by a specialized epithelial cell- ameloblast)

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3
Q

true or false: enamel is not the only one that does not have an unmineralized or preenamel formation stage

A

false

most of enamel has an immature stage (partially mineralized) and a mature stage (fully mineralized)

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4
Q

is enamel formation finite?

A

yes
ameloblast completes its enamel formative cycle once the thickness of enamel is reached at a site (most advanced coronally)

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5
Q

is enamel the first mineralized tissue to appear in a developing tooth?

A

no

dentin is the first to appear, enamel second

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6
Q

what does enamel subject to?

A

malformations (genetic and external factors), age changes, self-induced habits

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7
Q

does enamel have enclosed cells, nerves, or lymph vessels?

A

no

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8
Q

what is enamel tissue?

A

composite biological mineral with apatite crystals oriented in a complex 3d pattern

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9
Q

physical properties of enamel

A

most clinically significant tissue of tooth, esp at surface, pits, grooves, ridges, caps, cracks
hardest and most highly mineralized bioloogical tissue.
5 on mineral hardness scale. 1-talc, 10 diamond
withstands both shearing and impact forces well
brittle without dentin support
translucent
needs wet environment to maintain integrity***
subject to attrition, abrasion, erosion

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10
Q

what is attrition?

A

normal slow wearing away of tooth substance under the stress of mastication

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11
Q

what is microporosity?

A

pathways for diffusion of small molecules such as water, electrochemical effects on pore walls lead to carious lesions

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12
Q

what is remineralization?

A

mineral is returned to the molecular structure of enamel by way of the saliva. when demineralization exceeds remineralization, cavitation occurs

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13
Q

inorganic substance within enamel

A

96% by weight
hydroxyapatite crystals.
enamel crystals are larger and consist of more impurities than other 3 types

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14
Q

organic substance within enamel

A

1% by weight. enamel is the only one of the 4 mineralized tissue that does not contain collagen fiber - can dissolve in weak acid

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15
Q

water within enamel

A

3% by weight
distributed throughout the volume of enamel by ways of micropores between crystals and proteins.
most of water forms a hydration shell around each crystal.
its distribution is clinically important bc its the route of fluoride ions, calcium and phosphorous ions for remineralization and whitening substances artificial and natural substances, acidophilic microorganisms, age changes

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16
Q

what are the age changes of enamel?

A

wears slowly- attrition- darkens in color, composition of surface changes, fluoride increased at surface- reduced porocity- reduced susceptiility to caries.

17
Q

what are the 3 CEJ relationships?

A

most common: cementum overlaps enamel
next common: cementum meets enamel
least common: cemetum does not meet enamel

18
Q

DEJ configuration around tooth

A

scalloped at coronal areas: adaptation to occlusal forces

smooth at cervical areas: non- load bearing areas

19
Q

what are ameloblast?

A

columnar epithelial cells

20
Q

what are lines of retzius?

A

growth lines

21
Q

what is perikymata?

A

numerous small transverse ridges on the exposed surfaces of enamel
lines of retzius end on enamel surfaces as grooves. perikymata (ridges) are created between the grooves

22
Q

how are the structural components of enamel formed?

A

due to the direction and density of the apatite crystals in each site

23
Q

what are the three structural components of enamel?

A

enamel rods
enamel sheath
interrod substance

24
Q

enamel rods

A

structural unit of enamel
hydroxyapatite crystals are most dense in the center or core of the rod and run parallel to the long axis of the rod
each rod is formed by one ameloblast***

25
Q

enamel sheath

A

outer surface of the rod
crystals are less dense than those of core and run in different directions, higher % of organic substance
formed by one ameloblast along with the rod

26
Q

interrod substance

A

between he sheaths of rods
crystals ar more dense and run at different directions than those of the sheath
two or more amelobalst secrete the interrod substance

27
Q

what is the direction of rods?

A

right angles to dentin surface

28
Q

what are interrod striations?

A

each enamel rod is built up of segments separated by dark lines that give it a striated appearance.
segmented bc its secreted in a rhythmic manner- rest period of ameloblast marked by interrod striation

29
Q

what are the 3 hypomineralized enamel structures

A

enamel lamella
enamel tuft
enamel spindle

30
Q

enamel lamella

A

extend for varying depths from the surface of enamel and consist of longitudinally oriented defects filled with enamel protein or organic debris from the oral cavity
originates at enamel surface and passes toward dentin
clinical significance: due to their access by acidophilic microorganisms and to stain substances

31
Q

enamel tuft

A

tufts project from the DEJ for a short distance into enamel and contain greater concentration of enamel protein
clinical signicance: contributes to the spread of caries at the DEJ

32
Q

enamel spindle

A

spindles extend from the dentin across the DEJ into the enamel for a short distance
formed when before secretion of dentin and enamel begins, some cell processes of odontoblast extend between ameloblast and when enamel formation begins, the processes become embedded within the newly secreted enamel.
clinical signicance: contributes to spread of caries along the DEJ

33
Q

hunter schreager band

A

alternating dark and light bands of varying width- originate at the DEJ border and pass outward ending at some distance from the outer enamel surface: caused by the different direction of enamel rods in adjacent layers
change in rod direction is regarded as a functional adaptation, minimizing the risk of cleavage in the axial direction under the influence of masticatory forces

34
Q

where does differentiation first occur?

A

differentiation of inner epeithelial cells of the enamel organ into ameloblasts and of the peripheral cells of the dental papillar into odontoblasts begins in the coronalmost side of future dej

35
Q

how does enamel and dentin first form?

A

ameloblast form partially mineralized or immature enamel moving outward
odontoblast forming predentin: moving inward toward center of pulp

Oral Histology Exam 1 (5 decks)

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