PULP Introduction The dental pulp has its genesis in the 6 th week of 10 life during initiation of tooth development. It forms from cranial neural crest derived ectomesenchymal cells which have migrated cephalically over the developing fore brain and ventrally around the developing foregut. These cells migrate extensively. Some travel down the sides of the head into the maxilla and mandible. During tooth formation aggregates of the neural crest cells, form the individual dental papilla which eventually become dental pulp. Thus the papilla is the primordium of the pulp after dentinal forms it is called keep. Histogenesis continues and cells differentiate into odontoblasts and pulp. This process is due to embryonic induction and epithelial, mesenchymal interaction. Both these 1
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PULP
Introduction
The dental pulp has its genesis in the 6th week of 10 life during initiation
of tooth development.
It forms from cranial neural crest derived ectomesenchymal cells which
have migrated cephalically over the developing fore brain and ventrally around
the developing foregut. These cells migrate extensively. Some travel down the
sides of the head into the maxilla and mandible.
During tooth formation aggregates of the neural crest cells, form the
individual dental papilla which eventually become dental pulp.
Thus the papilla is the primordium of the pulp after dentinal forms it is
called keep. Histogenesis continues and cells differentiate into odontoblasts and
pulp.
This process is due to embryonic induction and epithelial, mesenchymal
interaction. Both these processes need cell to cell communication in the form
of:
1. Cytoplasmic process and gap junction.
2. Synthesis, release and diffusion of information molecules.
3. Information contained within cells derived, membrane delimited matrix
vesicles being shuttled between the tissues.
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Originally the pulp is large. It later attains normal dimension due to
pulpal migration and due to dentinal apposition. In the bell stage of tooth
development the blood vessels become established in the papilla.
There are 52 pulp organs seen 20 seen are primary and 32 permanent.
Total volume is primary – 2°C .2 CC
– 38°C .38 CC
Common features of pulps of all teeth are pulp chamber.
Pulp can be divided into
– Coronal pulp
– Radicular pulp
– Accessory canals
– Apical foramen
Coronal pulp
Centrally situated shows 6 surfaces
Roof or the occlusal portion
Mesial surface
Distal surface
Buccal surface
Lingual surface
Where the coronal pulp becomes the radicular pulp a cervical
constriction is seen.
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The pulp horns or cornua are protrusions that extend into the cusps of
each crown.
Radicular pulp
Anterior teeth have a single root canal and posteriors have multiple
where it is widest.
This is continuous with a PA connective tissue through the apical foramen.
The shape of the radicular pulp is tubular or funnel shaped. An inferior
projection of the coronal connective tissue extending from cervix to apex.
The caliber of the canal is greatest during development and decreases as
life increases.
Root walls may be interrupted by accessory canals / channels, lateral
canals, sec canals, apical ramifications.
Apical foramen
Average size – Maxillary – 4mm
Mandibular – 3mm
Location may change because of the various physiological factors like
mesial migration and tipping which will cause the apex to tilt.
This can be explained as follows:
Pressure on one wall will cause resorbtion of that wall but at the same
time deposition may be seen on the opposing wall.
May be lateral in position or it may branch at the tip to form 2 foramina.
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Accessory canals
May be seen any where from floor along the length of root.
Most commonly seen in: acpical are third
1. When the dentin is forming it might encounter a blood vessel and
therefore hard tissue will form around it.
2. Premature loss of root sheath cells because these cells will induce
formation of odontoblasts.
3. some times in molars they may pierce through the intra radicular
fork of the tooth and enlarge from the floor of the pulp chamber.
Cross description of pulps of maxillary and mandibular teeth
MX
CI
Showel shaped coronally with 3 short borns on the coronal roof tapering
down to a triangle root in cross section with the patient of triangle pointing
lingually.
Small spoon shaped round root at apex.
Cuspid – longest with an elliptical cross section.
Large occlusal cervical pulp with a mesial concavity on the cervical 1/3rd
of chamber devides into 2 funnel shaped roots similar but with only root.
Roughly rectangular cervical cross section with the greatest dimension
buccolingually and also demonstrating mesiobuccal prominence. 3 roots
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lingual is longest DB is shortest from the 1st molar to 3rd crowns get smaller and
roots closer.
MN
CI – smallest pulp and is long and narrow with a flattened elliptical shape in
C.S.
LI – It is the smallest.
C – Similar to but shorter than the maxillary canine.
1PM – Similar to the canine
2PM – Lingual horn is much smaller than the buccal horn.
M – Coronal cross section is rectangular mesiobuccal horn is highest
distolingual is lowest.
Structure of the pulp
Pulp is a specialized loose connective tissue – Structurally this character
implies that this tissue contains more cells and amorphous ground subs/unit
area than it does fibres.
The pulp shows 4 distinct zones:
1) The odontoblastic zone.
2) Subodontoblastic cell free zone of weil (which is not really cell free).
3) The cell rich zone.
4) Core of the pulp
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Cell free zone
This is a space in which the odontoblasts may move pulpward during
tooth development and lateral to a limited extent in furcationing teeth.
This zone is inconspicuous during early stages of rapid dentinogenesis
as odontoblast migration is greatest at that time.
This zone is most well defined in coronal pulp and its thickness is
around 40m. This zone is only cell free in haemotoxylin and eosin sections.
When special nerve stains are employed an extensive unmyelinated nerve
plexus is seen called the:
Subodontoblastic Nerve Plexus
From this plexus nerves emanate and arbourize on the odontoblasts (and
their processes).
They also pass between the cells to eventually terminate within the
dentinal tubules.
The cell free and cell rich zone both, are formed rather late in the
histogenesis of the pulp mostly after eruption.
Components of this zone are mostly ground subs. In which are seen
reticular argyrophylic fibres.
Apart from this some pericytes may be located in the capillary plexus:
Fibroblasts may be present to maintain and or produce fibrils.
Macrophages.
Cellular components of blood and lymphatic channels.
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Cell rich zone
This zone is more deeply situated pulpward. Seen in both coronal and
radicular pulp.
This zone contains:
1) Fibroblasts
2) Undifferentiated ectomesenchymal cells.
3) A rich capillary plexus.
These include:
1) Ground substance or intercellular matrix.
2) Fibres.
3) Cells
- Fibroblasts.
- Undifferentiated mesenchymal
- Odontoblasts
- Macrophages.
Ground substance or the inter cellular matrix is abundant in young
pulps.
It is gelatinous in consistency and dense. Its appearance varies from
finely granular to fibrillar and appears more dense in some areas with some
clear spaces left between various aggregates. The nature varies depending upon
the qualitative aspect of its fibre component.
Composition – consists of
- Acid mucopolysaccharides.
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- Protein polysaccharides compounds.
Glycosamino glycans Proteoglycans
During early development the presence of
- Chondroitin A & B
And hyaluronic acid has been demonstrated in abundance.
The ground substance lends support to the cells of the pulp.
It also serves as a means of transport of metabolites and
nutrients from cells to blood vessels as it is a highly diffusible medium.
Fibres
The fibres in the pulp include:
- Reticular / precollagen
- Collagenous
- Oxytalan / preelastic
- Elastic
The fibres change from development or stages to
advanced age, collagen fibres are very common most evidence states
that Type I is more common but recent studies have stated that both
Type I and III collagen fibres may be seen which are genetically
different.
The collagen fibres in the pulp are found throughout the
pulp mostly in apical region. In H & E stained sections they may be pink
but with silver stains are used they exhibit argyrophilia i.e. they appear
dark brown to black. These are the precollagenous fibers.
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These form a delicate network pursuing spiral or straight path.
Electron microscopy shows that fibrils exhibit typical 64nm cross
striations.
The large collagen fibrils vary from 10-100m in large.
In very young pulp fibres ranging from 10-12nm are seen. Their
significant is unknown.
After root completion the pulp matures and bundles of collagen fibres
increase in number.
They may be scattered throughout the root or they may be in bundles
especially in apical portion. These are termed as diffuse or bundle collagen
depending on appearance.
Their presence may be related eminence mental trauma.
The fiber bendles are most prevalent in the root canals especially near
the apical region.
Cells of the pulp
The pulp is composed of 4 major cell type
1. Odonto blasts
2. Un differentiated mesencymeal cells.
3. Fibro blasts
4. Cells like histiocytes / macro phage
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- Plasma Cells
- Most cells
The first 3 cell types are permanent resident of the dental pulp.
1. Odontoblasts
these are the largest and the second most prominent cell of the pulp the
first being the fabroblast.
They are seen adjacent to the predentin with the cell bodies in pulp and process
in dentin.
Size 5-7 m in diameter, 25 – 40 m in length
Cell bodies
Columnar with large oral nuclei. These fill the basal part of the cell.
Immediately adjacent to the nucleus is the rough endo plastic reticulum and the
gogli apparatus.
The cells lie every close to each other and the plasma membranes exhibit
junctional complexes. Towards the apex of the cell appears rough endo plasmic
reticulum.
Near the pulpal pre dentinal junction there are no cell organells. The clear
terminal part of the cell body and the adjacent inter cellular junction is
described by some as the terminal bar apparatus of the odontoblasts.
At this zone the cell consists to a diameter of 3-4 mm where the cell process
enters the predental tubule.
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The process contains no active dentinogenesis it shows certain mito chondria
and vesicles.
Efferent motor pathway
Has symphathetic fibres these enter through apicals foramen in the
turnica adventitia of arterioles, they travel with the vessels end in turnica media
of arterioles and their branches and capillaries.
These provide vasomotor control to circulation and regulates blood
flow.
An interesting point is the role of nerve fibres in dentinogenesis.
According to Ingle, Avery and colleagues reported that both
parasymptamathetic and sympathetic nerves innervate odontoblasts. Only the
nerves in the inferior alveolar nerve trunk influence odontoblastic function.
When this nerve is sectioned and a cavity prepared in dentin the
odontoblasts react and form sec dentin throughout the pulp rather than just
below the cavity.
So inferior alveolar nerve may contain parasymptomatically motor
nerves that regulate the rate of dentinogenesis.
Sympathetic nerves may also play a role in regulating the eruption as
follows. They regulate blood flow by opening / closing AV shunts this may
secondarily affect eruptive pressure.
During the early active phase of dentogenesis
The golgi apparatus is more prominent.
The rough endoplasmic reticules is more abundant.
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Numerous mitochondria are seen throughout the odontoblast.
Peripherally many vesicles are seen where there is evidence of protein
synthesis along the tubule wall the cell actually increase in size as its
process lengthens when the process becomes 2mm long it then many
times greater in volume than the allbody.
The odontoblasts may differ in shape throughout the pulp.
Tall columnar coronal pulp
Cuboidal in middle of the root.
Spindle shaped and ovoid – in apex
Therefore here they resemble osteocytes, the processes being the only
differentiation.
Irregularly in near apical foramen appearance.
Derived from the cranial neural crest cells.
2) Fibroblasts
3) Undifferentiated mesenchymal cells
These cells are seen primarily in the young pulp throughout the pulp the
mature pulp also contains a relatively large population.
These cells are seen in – cell rich zone, pulp tissue proper.
They are characterized by – undifferentiated uncommitted appearance.
Under electron microscope they appear large, polyhedral cells. With a
large lightly staining centrally placed nuclear.
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They have abundant cytoplasm and peripheral cytoplasmic extensions.
Nuclear contains heterochromatin cytoplasm is rich in free ribosomes
and poly ribosomes.
Microtubules and microfilaments are present which allow the cell to
wander this wandering movement is via
Fibroblasts
The fibroblasts are seen in greatest no. in the pulp.
Numerous in coronal portion where the cell rich zone is seen.
In the central pulp or core it is most prevalent.
They are derived from undifferentiated M. cells.
They exist in 2 states
Active fibroblasts Inactive fibrocytes.
They are stellate cells with processes which join other
They show Elliptical centrally placed nuclear which resides within a