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Oral Histology > dentin structure > Flashcards

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
Q

what type of dentin is put down in response to serve injury or OB die and is it fast or slow

A

reparative dentin

slow to react but FAST depostiion

26
Q

Crystals that fail to coalesce and mineralize form hypomineralized regions called

A

interglobular dentin

27
Q

what are the 2 patterns of dentin mineralization

A
  1. globular 2. linear
28
Q

what represent the weekly deposition of dentin
* Lines appear at right angles to dentin tubule

A

Incremental Lines of Von Ebner

29
Q

can we see Incremental Lines of Von Ebner

A

NO!

30
Q

what are exaggered lines of Von Ebner called

A

contour lines of owen

31
Q

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

A

contour lines of owen

32
Q

what appears as line demarcating tertiary dentin at point of injury.

A

Calciotraumatic line

33
Q

what appears yellow when viewed by transmitted light – tetracycline binds to calcium of hydroxyapatite crystals

A

tetracycline bands

once 8 y/o, cannot get anymore

34
Q

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

A

neonatal lines

35
Q

function of dentin tubules

A

allows for diffusion of nutrients

36
Q

what do dentin tublues look like at the crown

A

s shaped

37
Q

what do dentin tubules look like at the root

A

straight lines but bends at CDJ = granular layer (hypominerlaized)

38
Q

contents of dentin tubules

A
  1. Odontoblastic process
  2. Unmyelinated sensory nerves endings extend short distance from pulp into tubule
  3. Dentinal fluid
39
Q

what are dead tracts

A

-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
Q

_____________ seals off such dead tracts at their pulpal extremity, thereby protecting the pulp from infection

A

Reparative dentin

41
Q

region between the tubules

A

intertubular dentin

42
Q

where is intertubular dentin

A

in crown and root in circumpulpal region

43
Q

region of dentin that forms wlal of tubule

A

peritubular dentin

44
Q

is peritubular dentin hypo or hypermineralizaed

A

hypermineralized

45
Q

is peritubular found in interglobular dentin

A

NO

46
Q

where can you find peritubular dentin

A

crown and root

47
Q

in caries attack, one of the first regions demineralized is ______________– outcome is increased tubule diameter and faster spread of toxins and bacteria.

A

peritubular dentin

48
Q

dentin tubules become filled with hypermineralized dentin

A

sclerotic dentin - aging

49
Q

region where calcospherites failed to fuse

A

interglobular dentin

hypomineralized!!

50
Q

region where dentin tubules meet cementum and hypomineralized in root, closet to CEJ.

ONLY visible in dry ground!

A

granular layer of tomes

Salt and pepper

51
Q

-represents the interface between the dentin and cementum
* First layer deposited in ROOT formation but is delayed in completing mineralization until cementum is deposited.

A

hyaline layer of hopewell smith

last place mineralized

52
Q

age related changes in dentin

A
  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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