Dentin Histo Study Guide Flashcards
Vital dentin vs non vital
Vital Dentin is slightly elastic – (i.e. dentin with odontoblastic processes). Non-vital loses
elasticity and may fracture when stressed.
Primary Dentin
bulk of tooth dentin – all dentin from DEJ or DCJ to secondary dentin
Mantle Dentin
approximately 150 ųm wide
see fig. 8-2 and notice interglobular dentin layer
Circumpulpal Dentin
all the primary and secondary dentin under the mantle dentin, but does not include mantle dentin
Secondary Dentin
the dentin that forms after the crown is in occlusion and the roots are nearly completed (fig. 8-4)
Tertiary or Reparative Dentin
function and how long it takes to form
protects the pulp from further injury (figs 8-5, 8-6)
–dentin produced by irritation (pathology) takes about one month to form.
Features of tertiary or reparative dentin
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
tertiary or reparative dentin may have cell inclusions called
osteodentin-this is reparative dentin that histologically resembles bone
Where does reparative/tertiary dentin build up
builds up in the pulpal space-may reduce this space
Predentin (what, from what)
Not yet mineralized
produced by odontoblasts-usually produces an even predentin zone
Formation of predentin
Organic matrix given off by odontoblasts that resembles osteoid
Inorganic minerals are added, mineralization occurs producing mature dentin at the predentin-dentin junction
Dentin Tubular and Intertubular Relations, where do the tubules branch? what are there Shape?
DEJ and DCJ- the crown has dentin tubules that have an S-shaped curve
Describe the dentin tubules
S-shaped curve
tubes are very narrow and long-compared to a garden hose 1” in diameter and 100’ long
How much dentin is exposed next to the pulp (mm^2)
30,000-50,000/mm^2
As dentin tubules approach the DEJ and DCJ they get
smaller in diameter
Dentin tubules are _____ in diameter at the pulp than the DEJ and DCJ
4x larger
Tubules have numerous branches called and contain
canaliculi and contain small odontoblastic processes
Peritubular dentin is also called
intratubular dentin
Tubules contain what in them
watery dentinal fluid
What produces the watery dentinal fluid
the pulp
Dentinal tubules extend into the enamel by way of
enamel spindles
Features of intratubular dentin (aka peritubular dentin) (2)
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)
With a mild irritation (i.e.) the dentin tubule may fill with dentin and is called
sclerotic dentin
Function of sclerotic dentin
sclerotic dentin (acts as a barrier to carries) by filling dentin tubules
The rhythmic laying down of dentin leads to what
incremental lines of dentin
incremental line/imbrications (define)
lines of hypermineralized dentin perpendicular to the dentin tubules
another name for these imbrication lines
von ebner
Imbrication line of von Ebner are spread out every
20um
5 day marker of imbrication lines
Embrication lines of von ebner
For 5 days, predentin is laid down _____ a day
4u/day
predentin is mineralized to form
von ebner lines
Neonatal line
a disturbance in dentin mineralization at birth which is also often seen in enamel which separates prenatal and post-dentin and enamel formation
Neonatal lines seperate what
in enamel which separates prenatal and post-dentin and enamel formation
Granular layer is also referred to as
Tome’s granular layer
Granular layer/tome’s granular layer
a looping of dentinal tubules only seen in root dentin- seen at the DCJ and next to the cementum onlyq
Where do you find Granular layer/Tome’ granular layer
seen at the DCJ-next to the cementum
odontoblastic process
a cytoplasmic extension of the odontoblast-gives dentin its vitality
How long are cytoplasmic extension
extend to DEJ and DCJ, may even extend into enamel as an enamel spindle
if the odontoblastic process is missing from the tubule, it is called what
a dead tract filled with air
The open dead tract stimulates the formation of
reparative dentin or sclerotic dentin
may fill the tubule
Note how size of tubule varies depending upon location (fig. 8-20)
It is large near the pulp ( C ) and small at the DEJ ( A ).
Dentinoenamel Junction – see enamel spindles (fig 8-16)
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.
Permeability –
see Pulpal fluid when tubule is exposed (see pulp chapter diagrams – fig.8-
20)
Sclerotic Dentin –
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.
Globular and Interglobular Dentin (fig 8-2)
- 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.
If you expose 1 mm3 of dentin, about how many dentin tubules are exposed?
Next to the pulp: 30k-50k tubules per mm^3
Describe how a necrotic odontoblast could be replaced. What cell type produces reparative dentin?
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.
Which has more tubules, secondary dentin or reparative dentin?
Secondary dentin has more tubules
than tertiary/reparative dentin.
define primary dentin
bulk of the tooth’s dentin that forms prior to eruption; all of the dentin from
DEJ or DCJ to secondary dentin
Define secondary dentin
the dentin that forms after the crown is in occlusion and the roots are nearly
completed
Define Tertiary dentin/Reparative dentin
(function, tubules?, how long to form?, other features?)
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)
Mantle dentin
approximately 150 micrometers wide; product of immature, not yet fully
differentiated odontoblasts
Define Sclerotic dentin (sclerosed/transparent dentin):
tubule is occluded with mineralized dentin;
this reduces permeability of dentin and is a result of mild irritation (caries)…this is DESIRABLE
Define Dentin dead tracts
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)
Define Peritubular dentin:
dentin that directly surrounds the tubules (more mineralized than
intertubuler)
Define Intertubular dentin:
dentin located between or around the dentinal tubules
Globular and interglobular dentin:
an area of dentin that is hypomineralized (interglobular),
surrounded by rounded, mineralized dentin (globular) – most commonly located just under
mantle dentin
Define Circumpulpal dentin:
all the primary and secondary dentin under the mantle dentin, but doesn’t
include mantle dentin
Define Predentin:
produced by odontoblasts, but not yet mineralized dentin at the pulpal border
State how the size of the dentinal tubules varies from a dentin tubule near the pulp to the DEJ.
Density and diameter of tubules DECREASE as you go from pulp to DEJ…
The closer to the pulp, the larger the tubules are!
In what
layer of dentin does branching of the odontoblasts occur?
Branching of the odontoblasts/tubules begins at the DEJ and DCJ (?)
Draw how an odontoblast occupies a dentin tubule and terminates as an enamel spindle.
What fluid
fills the dentinal tubule?
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.
Explain how sclerotic and reparative dentin form.
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
How would these dentins protect the dental pulp?
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
How soon after pulpal injury does reparative dentin begin to form?
~30 days
Dentin sclerosis =
thickening of peritubular dentin and (up to) complete obliteration of dentin
tubules
Explain how lines of von Ebner form
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.
Lines of von Ebner-Are these lines parallel or perpendicular to the dentin tubules?
These lines
are perpendicular to the dentin tubules. Yes
Could a tooth have both dentin and enamel neonatal lines?
Yes, neonatal lines can be seen in both enamel and
dentin (lines of Retzius in enamel/contour lines of Owen in dentin).
What structures make up Tomes’ granular cell layer? Where is this layer found?
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.
State how predentin forms and then becomes mature dentin.
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)
