Dentin Histo Study Guide

Question 1

Vital dentin vs non vital

Answer 1

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

Question 2

Primary Dentin

Answer 2

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

Question 3

Mantle Dentin

Answer 3

approximately 150 ųm wide

see fig. 8-2 and notice interglobular dentin layer

Question 4

Circumpulpal Dentin

Answer 4

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

Question 5

Secondary Dentin

Answer 5

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

Question 6

Tertiary or Reparative Dentin

function and how long it takes to form

Answer 6

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

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

Question 7

Features of tertiary or reparative dentin

Answer 7

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

Question 8

tertiary or reparative dentin may have cell inclusions called

Answer 8

osteodentin-this is reparative dentin that histologically resembles bone

Question 9

Where does reparative/tertiary dentin build up

Answer 9

builds up in the pulpal space-may reduce this space

Question 10

Predentin (what, from what)

Answer 10

Not yet mineralized

produced by odontoblasts-usually produces an even predentin zone

Question 11

Formation of predentin

Answer 11

Organic matrix given off by odontoblasts that resembles osteoid

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

Question 12

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

Answer 12

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

Question 13

Describe the dentin tubules

Answer 13

S-shaped curve

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

Question 14

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

Answer 14

30,000-50,000/mm^2

Question 15

As dentin tubules approach the DEJ and DCJ they get

Answer 15

smaller in diameter

Question 16

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

Answer 16

4x larger

Question 17

Tubules have numerous branches called and contain

Answer 17

canaliculi and contain small odontoblastic processes

Question 18

Peritubular dentin is also called

Answer 18

intratubular dentin

Question 19

Tubules contain what in them

Answer 19

watery dentinal fluid

Question 20

What produces the watery dentinal fluid

Answer 20

the pulp

Question 21

Dentinal tubules extend into the enamel by way of

Answer 21

enamel spindles

Question 22

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

Answer 22

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)

Question 23

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

Answer 23

sclerotic dentin

Question 24

Function of sclerotic dentin

Answer 24

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

Question 25

The rhythmic laying down of dentin leads to what

Answer 25

incremental lines of dentin

Question 26

incremental line/imbrications (define)

Answer 26

lines of hypermineralized dentin perpendicular to the dentin tubules

Question 27

another name for these imbrication lines

Answer 27

von ebner

Question 28

Imbrication line of von Ebner are spread out every

Answer 28

20um

Question 29

5 day marker of imbrication lines

Answer 29

Embrication lines of von ebner

Question 30

For 5 days, predentin is laid down _____ a day

Answer 30

4u/day

Question 31

predentin is mineralized to form

Answer 31

von ebner lines

Question 32

Neonatal line

Answer 32

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

Question 33

Neonatal lines seperate what

Answer 33

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

Question 34

Granular layer is also referred to as

Answer 34

Tome's granular layer

Question 35

Granular layer/tome's granular layer

Answer 35

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

Question 36

Where do you find Granular layer/Tome' granular layer

Answer 36

seen at the DCJ-next to the cementum

Question 37

odontoblastic process

Answer 37

a cytoplasmic extension of the odontoblast-gives dentin its vitality

Question 38

How long are cytoplasmic extension

Answer 38

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

Question 39

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

Answer 39

a dead tract filled with air

Question 40

The open dead tract stimulates the formation of

Answer 40

reparative dentin or sclerotic dentin | may fill the tubule

Question 41

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

Answer 41

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

Question 42

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

Answer 42

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.

Question 43

Permeability –

Answer 43

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

Question 44

Sclerotic Dentin –

Answer 44

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.

Question 45

Globular and Interglobular Dentin (fig 8-2)

Answer 45

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.

Question 46

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

Answer 46

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

Question 47

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

Answer 47

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.

Question 48

Which has more tubules, secondary dentin or reparative dentin?

Answer 48

Secondary dentin has more tubules | than tertiary/reparative dentin.

Question 49

define primary dentin

Answer 49

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

Question 50

Define secondary dentin

Answer 50

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

Question 51

# Define Tertiary dentin/Reparative dentin (function, tubules?, how long to form?, other features?)

Answer 51

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)

Question 52

Mantle dentin

Answer 52

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

Question 53

Define Sclerotic dentin (sclerosed/transparent dentin):

Answer 53

tubule is occluded with mineralized dentin; | this reduces permeability of dentin and is a result of mild irritation (caries)...this is DESIRABLE

Question 54

Define Dentin dead tracts

Answer 54

``` 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) ```

Question 55

Define Peritubular dentin:

Answer 55

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

Question 56

Define Intertubular dentin:

Answer 56

dentin located between or around the dentinal tubules

Question 57

Globular and interglobular dentin:

Answer 57

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

Question 58

Define Circumpulpal dentin:

Answer 58

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

Question 59

Define Predentin:

Answer 59

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

Question 60

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

Answer 60

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

Question 61

In what | layer of dentin does branching of the odontoblasts occur?

Answer 61

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

Question 62

Draw how an odontoblast occupies a dentin tubule and terminates as an enamel spindle. What fluid fills the dentinal tubule?

Answer 62

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.

Question 63

Explain how sclerotic and reparative dentin form.

Answer 63

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

Question 64

How would these dentins protect the dental pulp?

Answer 64

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

Question 65

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

Answer 65

~30 days

Question 66

Dentin sclerosis =

Answer 66

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

Question 67

Explain how lines of von Ebner form

Answer 67

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.

Question 68

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

Answer 68

These lines | are perpendicular to the dentin tubules. Yes

Question 69

Could a tooth have both dentin and enamel neonatal lines?

Answer 69

Yes, neonatal lines can be seen in both enamel and | dentin (lines of Retzius in enamel/contour lines of Owen in dentin).

Question 70

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

Answer 70

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.

Question 71

State how predentin forms and then becomes mature dentin.

Answer 71

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)