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dentin structure Flashcards

1
Q

what forms a protective covering for the pulp and supports the overlying enamel and cementum

A

dentin

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2
Q

T/F

dentin is acellular, avascular, limited repair, no remodeling, located in crown and root and depositied over life of tooth

A

TRUE

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3
Q

what is the chemical composition of dentin

A

70 in-org
20 org
10 water

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4
Q

are the non-fib and fib the same proteins as in enamel and cementum?

A

NO! totally different ones

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5
Q

T/F

dentin has less elasticity and tensile strength than enamel

A

FALSE

it has more elasticity and tensile strength than enamel due to collagen!

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6
Q

is dentin permeably?

A

yes

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7
Q

2 regions of dentin

A

coronal and radicular

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8
Q

what are the 2 types of coronal dentin

A

mantle and circumpulpal

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9
Q

what are the 2 types of radicular dentin

A

hyaline layer of hopewell smith and circumpulpal

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10
Q

is peritubular dentin low or highly mineralized

A

highly!

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11
Q

hypomineralized regions in CROWN

A

mantle dentin and interglobular dentin

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12
Q

hyperminerzliaed regions in CROWN and ROOT

A

sclerotic

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13
Q

hypomineralized regions in ROOT

A

granular layer of tomes and may have some interglobular too

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14
Q

when does deposition of coronal dentin start

A

Deposition starts at end of bell stage through apposition (pre-eruptive)

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15
Q

when does deposition of radicular dentin start

A

Deposition starts during root formation (pre-functional
eruptive; Intraosseous )

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16
Q

does coronal dentin have a fast or slow rate of deposition

A

fast

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17
Q

does radicular dentin have a fast or slow rate of depostion

A

slower

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18
Q

what is deposited during pre-eruptive phase and pre-functional eruptive phase

A

primary dentin

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19
Q

what is the outer layer of dentin closest to DEJ ; first mineralized ( 3-5% less mineralized vs rest of crown) 0.15- .0.20 mm thickness in crown
and collagen fibers-deposited in crown perpendicular to DEJ

A

MANTLE dentin

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20
Q

what Surrounds pulp chamber - recognized in both crown and root
o Collagen fiber tightly packed arranged parallel to long axis of tooth 6-8 mm in thickness in crown/ thinner in root
* Slower rate of mineralization/ deposition than mantle
* Regular arrangement of dentin tubules –
* S-shaped curve in crown ( due to odontoblasts crowded)
* Horizontal rows in root (perpendicular to cementum )

A

circumpulpal dentin

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21
Q

what is deposited after root formation is complete and tooth is in occlusion;- (post-eruptive) secondary and triggered by physiological stimuli i.e aging, occlusal forces; abrasive foods

A

SECONDARY dentin

22
Q

what dentin is deposited over life of tooth

A

secondary dentin

23
Q

what is deposition triggered by pathological stimulus – (post-eruptive

A

tertiary dentin

24
Q

what type of dentin is put down in response to caries, restoration, attrition and erosion and is it fast or slow

A

reactionary dentin

SLOW deposition

25
what type of dentin is put down in response to serve injury or OB die and is it fast or slow
reparative dentin slow to react but FAST depostiion
26
Crystals that fail to coalesce and mineralize form hypomineralized regions called
interglobular dentin
27
what are the 2 patterns of dentin mineralization
1. globular 2. linear
28
what represent the weekly deposition of dentin * Lines appear at right angles to dentin tubule
Incremental Lines of Von Ebner
29
can we see Incremental Lines of Von Ebner
NO!
30
what are exaggered lines of Von Ebner called
contour lines of owen
31
what represent accentuated incremental lines (Von Ebner) which occur due to changes in mineralization over time * Appear as wide lines run perpendicular to dentin tubules
contour lines of owen
32
what appears as line demarcating tertiary dentin at point of injury.
Calciotraumatic line
33
what appears yellow when viewed by transmitted light -- tetracycline binds to calcium of hydroxyapatite crystals
tetracycline bands once 8 y/o, cannot get anymore
34
what are are hypomineralized regions that show the “trauma of birth” and disrupts the incremental deposition of the enamel and dentin in the crown. The line demarcates the boundary between the prenatal and postnatal periods of hard tissue deposition
neonatal lines
35
function of dentin tubules
allows for diffusion of nutrients
36
what do dentin tublues look like at the crown
s shaped
37
what do dentin tubules look like at the root
straight lines but bends at CDJ = granular layer (hypominerlaized)
38
contents of dentin tubules
1. Odontoblastic process 2. Unmyelinated sensory nerves endings extend short distance from pulp into tubule 3. Dentinal fluid
39
what are dead tracts
-Empty dentin tubule –odontoblastic process disintegrates/ retracts -Increase with age due loss of odontoblasts cell numbers -Site of bacteria entry into pulp -Visible by light microscopy – appear black due to air in Dry Ground section -Often appears in association with sclerotic and tertiary
40
_____________ seals off such dead tracts at their pulpal extremity, thereby protecting the pulp from infection
Reparative dentin
41
region between the tubules
intertubular dentin
42
where is intertubular dentin
in crown and root in circumpulpal region
43
region of dentin that forms wlal of tubule
peritubular dentin
44
is peritubular dentin hypo or hypermineralizaed
hypermineralized
45
is peritubular found in interglobular dentin
NO
46
where can you find peritubular dentin
crown and root
47
in caries attack, one of the first regions demineralized is ______________– outcome is increased tubule diameter and faster spread of toxins and bacteria.
peritubular dentin
48
dentin tubules become filled with hypermineralized dentin
sclerotic dentin - aging
49
region where calcospherites failed to fuse
interglobular dentin hypomineralized!!
50
region where dentin tubules meet cementum and hypomineralized in root, closet to CEJ. ONLY visible in dry ground!
granular layer of tomes Salt and pepper
51
-represents the interface between the dentin and cementum * First layer deposited in ROOT formation but is delayed in completing mineralization until cementum is deposited.
hyaline layer of hopewell smith last place mineralized
52
age related changes in dentin
1. thickness due to 2 and 3 dentin 2. decrease in permeability 3. increase response rate to attrition/caries 4. decrease in ability to repair

Oral Histology (12 decks)

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