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Oral Bio > Dentin Histo Study Guide > Flashcards

Dentin Histo Study Guide Flashcards

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1
Q

Vital dentin vs non vital

A

Vital Dentin is slightly elastic – (i.e. dentin with odontoblastic processes). Non-vital loses
elasticity and may fracture when stressed.

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2
Q

Primary Dentin

A

bulk of tooth dentin – all dentin from DEJ or DCJ to secondary dentin

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3
Q

Mantle Dentin

A

approximately 150 ųm wide

see fig. 8-2 and notice interglobular dentin layer

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4
Q

Circumpulpal Dentin

A

all the primary and secondary dentin under the mantle dentin, but does not include mantle dentin

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5
Q

Secondary Dentin

A 
the	dentin	that	forms	after	the	crown	is	in	occlusion	and	the	roots	are
nearly	completed	(fig.	8-4)
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6
Q

Tertiary or Reparative Dentin

function and how long it takes to form

A

protects the pulp from further injury (figs 8-5, 8-6)

–dentin produced by irritation (pathology) takes about one month to form.

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7
Q

Features of tertiary or reparative dentin

A

Fewer tubules-most common type of reparative dentin

may have cell inclusions called osteodentin-this is reparative dentin that histologically resembles bone

Builds up in pulpal space-may greatly reduce pulpal space

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8
Q

tertiary or reparative dentin may have cell inclusions called

A

osteodentin-this is reparative dentin that histologically resembles bone

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9
Q

Where does reparative/tertiary dentin build up

A

builds up in the pulpal space-may reduce this space

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10
Q

Predentin (what, from what)

A

Not yet mineralized

produced by odontoblasts-usually produces an even predentin zone

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11
Q

Formation of predentin

A

Organic matrix given off by odontoblasts that resembles osteoid

Inorganic minerals are added, mineralization occurs producing mature dentin at the predentin-dentin junction

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12
Q

Dentin Tubular and Intertubular Relations, where do the tubules branch? what are there Shape?

A

DEJ and DCJ- the crown has dentin tubules that have an S-shaped curve

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13
Q

Describe the dentin tubules

A

S-shaped curve

tubes are very narrow and long-compared to a garden hose 1” in diameter and 100’ long

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14
Q

How much dentin is exposed next to the pulp (mm^2)

A

30,000-50,000/mm^2

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15
Q

As dentin tubules approach the DEJ and DCJ they get

A

smaller in diameter

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16
Q

Dentin tubules are _____ in diameter at the pulp than the DEJ and DCJ

A

4x larger

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17
Q

Tubules have numerous branches called and contain

A

canaliculi and contain small odontoblastic processes

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18
Q

Peritubular dentin is also called

A

intratubular dentin

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19
Q

Tubules contain what in them

A

watery dentinal fluid

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20
Q

What produces the watery dentinal fluid

A

the pulp

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21
Q

Dentinal tubules extend into the enamel by way of

A

enamel spindles

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22
Q

Features of intratubular dentin (aka peritubular dentin) (2)

A

Hypermineralized compared to intertubular dentin

With a mild irritation (i.e.) the dentin tubule may fill with dentin and is called sclerotic dentin (acts as a barrier to carries)

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23
Q

With a mild irritation (i.e.) the dentin tubule may fill with dentin and is called

A

sclerotic dentin

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24
Q

Function of sclerotic dentin

A

sclerotic dentin (acts as a barrier to carries) by filling dentin tubules

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25
Q

The rhythmic laying down of dentin leads to what

A

incremental lines of dentin

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26
Q

incremental line/imbrications (define)

A

lines of hypermineralized dentin perpendicular to the dentin tubules

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27
Q

another name for these imbrication lines

A

von ebner

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28
Q

Imbrication line of von Ebner are spread out every

A

20um

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29
Q

5 day marker of imbrication lines

A

Embrication lines of von ebner

30
Q

For 5 days, predentin is laid down _____ a day

A

4u/day

31
Q

predentin is mineralized to form

A

von ebner lines

32
Q

Neonatal line

A

a disturbance in dentin mineralization at birth which is also often seen in enamel which separates prenatal and post-dentin and enamel formation

33
Q

Neonatal lines seperate what

A

in enamel which separates prenatal and post-dentin and enamel formation

34
Q

Granular layer is also referred to as

A

Tome’s granular layer

35
Q

Granular layer/tome’s granular layer

A

a looping of dentinal tubules only seen in root dentin- seen at the DCJ and next to the cementum onlyq

36
Q

Where do you find Granular layer/Tome’ granular layer

A

seen at the DCJ-next to the cementum

37
Q

odontoblastic process

A

a cytoplasmic extension of the odontoblast-gives dentin its vitality

38
Q

How long are cytoplasmic extension

A

extend to DEJ and DCJ, may even extend into enamel as an enamel spindle

39
Q

if the odontoblastic process is missing from the tubule, it is called what

A

a dead tract filled with air

40
Q

The open dead tract stimulates the formation of

A

reparative dentin or sclerotic dentin

may fill the tubule

41
Q

Note how size of tubule varies depending upon location (fig. 8-20)

A

It is large near the pulp ( C ) and small at the DEJ ( A ).

42
Q

Dentinoenamel Junction – see enamel spindles (fig 8-16)

A

Note the dentin tubule branch in the outer mantle dentin as seen in fig. 8-8. This is thought
to produce added dentin sensitivity if this area is exposed to irritants.

43
Q

Permeability –

A

see Pulpal fluid when tubule is exposed (see pulp chapter diagrams – fig.8-
20)

44
Q

Sclerotic Dentin –

A

Tubule is occluded with mineralized dentin. This reduces permeability of
dentin and is a result of mild irritation (e.g. caries) (fig. 8-19)
Is sometimes referred to as transparent dentin and is desirable.

45
Q

Globular and Interglobular Dentin (fig 8-2)

A
  1. Defined – An area of dentin that is hypo mineralized (interglobular) surrounded by
    rounded mineralized dentin (globular) 2. Most common location is just under the mantle dentin 3. Dentinal tubules are present running through globular and interglobular dentin.
46
Q

If you expose 1 mm3 of dentin, about how many dentin tubules are exposed?

A

Next to the pulp: 30k-50k tubules per mm^3

47
Q

Describe how a necrotic odontoblast could be replaced. What cell type produces reparative dentin?

A

A necrotic odontoblast could be replaced with dentin sclerosis (thickening of peritubular dentin),

dead tracts (air filled tubule, odontoblastic process is lost)

or tertiary dentin (which produces
reparative dentin to prevent the pulp from further injury).

Secondary dentin has more tubules
than tertiary/reparative dentin.

48
Q

Which has more tubules, secondary dentin or reparative dentin?

A

Secondary dentin has more tubules

than tertiary/reparative dentin.

49
Q

define primary dentin

A

bulk of the tooth’s dentin that forms prior to eruption; all of the dentin from
DEJ or DCJ to secondary dentin

50
Q

Define secondary dentin

A

the dentin that forms after the crown is in occlusion and the roots are nearly
completed

51
Q

Define Tertiary dentin/Reparative dentin

(function, tubules?, how long to form?, other features?)

A

protects the pulp from further injury (a dentin produced by
irritation/pathology, which takes about 1 month to form)…

has fewer tubules and may have cell
inclusions called osteodentin (which is reparative dentin that histologically resembles bone)

52
Q

Mantle dentin

A

approximately 150 micrometers wide; product of immature, not yet fully
differentiated odontoblasts

53
Q

Define Sclerotic dentin (sclerosed/transparent dentin):

A

tubule is occluded with mineralized dentin;

this reduces permeability of dentin and is a result of mild irritation (caries)…this is DESIRABLE

54
Q

Define Dentin dead tracts

A 
if an odontoblastic process is missing from a tubule and the tubule is filled
with air (this open dead tract stimulates the formation of reparative dentin, or sclerotic dentin
may fill the tubule)
55
Q

Define Peritubular dentin:

A

dentin that directly surrounds the tubules (more mineralized than
intertubuler)

56
Q

Define Intertubular dentin:

A

dentin located between or around the dentinal tubules

57
Q

Globular and interglobular dentin:

A

an area of dentin that is hypomineralized (interglobular),
surrounded by rounded, mineralized dentin (globular) – most commonly located just under
mantle dentin

58
Q

Define Circumpulpal dentin:

A

all the primary and secondary dentin under the mantle dentin, but doesn’t
include mantle dentin

59
Q

Define Predentin:

A

produced by odontoblasts, but not yet mineralized dentin at the pulpal border

60
Q

State how the size of the dentinal tubules varies from a dentin tubule near the pulp to the DEJ.

A

Density and diameter of tubules DECREASE as you go from pulp to DEJ…
The closer to the pulp, the larger the tubules are!

61
Q

In what

layer of dentin does branching of the odontoblasts occur?

A

Branching of the odontoblasts/tubules begins at the DEJ and DCJ (?)

62
Q

Draw how an odontoblast occupies a dentin tubule and terminates as an enamel spindle.

What fluid
fills the dentinal tubule?

A

Watery, dentinal fluid fills the tubules, and this fluid is produced by the pulp and fills the dentin
tubules, extending by way of enamel spindles.

63
Q

Explain how sclerotic and reparative dentin form.

A

a. Dentin sclerosis = thickening of peritubular dentin and (up to) complete obliteration of dentin
tubules
i. Deposition of apatite crystals and collagen in dentinal tubules caused by irritating
stimuli (caries, erosion, attrition, cavity preparation)

Tertiary dentin = results from pulp stimulation

i. Only in localized areas along dentin-pulp interface
ii. Correspond to those zones of dentin where tubules have been exposed

64
Q

How would these dentins protect the dental pulp?

A

Dentin sclerosis:
This blocking of tubules is a defensive reaction and part of the aging process
iv. EX: if a patient brushes too hard and removes enamel, the tubules will close to protect
the pulp (living dentin can occlude tubules if stimuli is slow enough)

Tertiary dentin:

Reparative = newly recruited odontoblasts (from undifferentiated cells of the pulp)
1. Forms after about a month

65
Q

How soon after pulpal injury does reparative dentin begin to form?

A

~30 days

66
Q

Dentin sclerosis =

A

thickening of peritubular dentin and (up to) complete obliteration of dentin
tubules

67
Q

Explain how lines of von Ebner form

A

Imbrication lines of von Ebner (every 20 micrometers) are a 5 day marker. For 5 days, predentin
is laid down 4 micrometers/day, then this is mineralized, producing a von Ebner line.

68
Q

Lines of von Ebner-Are these lines parallel or perpendicular to the dentin tubules?

A

These lines

are perpendicular to the dentin tubules. Yes

69
Q

Could a tooth have both dentin and enamel neonatal lines?

A

Yes, neonatal lines can be seen in both enamel and

dentin (lines of Retzius in enamel/contour lines of Owen in dentin).

70
Q

What structures make up Tomes’ granular cell layer? Where is this layer found?

A

Tomes’ granular layer is a looping of the terminal portions of dentinal tubules. It is only seen in
root dentin, at the DCJ (occurs next to cementum). It is a structural defect (hypomineralized
dentin) of unknown origin.

71
Q

State how predentin forms and then becomes mature dentin.

A

Predentin is produced by odontoblasts. Odontoblasts lay down an organic matrix that resembles
osteoid, then inorganic minerals are added. Mineralization occurs, producing mature dentin at
the predentin-dentin junction (it starts outwards at the active mineralization front, or calcium
globule and then continues towards the pulp)

Oral Bio (9 decks)

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