Download PULP

GENERAL FEATURES
 Every
person normally has a total of 52 pulp organs,
32 in the permanent & 20 in the primary teeth.
 The
total volumes of all the permanent teeth pulp
organs is 0.38 cc.
 The mean volume of a single adult human pulp is
0.02 cc.
 Molar
pulps are 3 to 4 times larger than incisor pulps.
 Cuspid has the longest pulp.
 Mandibular central incisor has the smallest pulp.
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 The
average size of apical foramen of the maxillary teeth
in the adult is 0.4 mm.
 In
the mandibular teeth it is slightly smaller, being
smaller, being 0.3 mm in diameter.
ACCESSORY CANALS
 Found in apical third region & furcation region.
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 The
average length of time a primary pulp functions in
the oral cavity is only about 8.3 years.
 This
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amount of time can be divided into three periods :Pulp organ growth
Pulp maturation
Pulp regression
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 Pulp
of the permanent teeth undergoes development
for about 12 years, 4 months.
 The
maxillary arches require slightly longer to
complete each process of development than do the
mandibular arches.
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The pulp is circumscribed by the specialized odontogenic
region composed of : The
odontoblasts (the dentin forming cells)
 The
cell-free zone (Weil’s zone), and
 The
cell-rich zone
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 Are
the most numerous cell types in the pulp.
 Function in collagen fiber formation .
 Have the typical stellate shape & extensive processes
that contact & are joined by intercellular junctions.
 Have abundant rough-surfaced endoplasmic reticulum,
mitochondria & other cell organelles.
 Also have the capability of ingesting & degrading this
same matrix.
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 In
the older pulp, they appear rounded or spindle
shaped with short processes & exhibit fewer
intracellular organelles. They are then termed
fibrocytes.
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 They
are the primary cells in the very young pulp.
 Only
a few are seen in the pulps after root
completion.
 Appear
larger than fibroblasts.
 Are
polyhedral in shape with peripheral processes &
large oval nuclei.
 Are
found along pulp vessels, in the cell-rich zone &
scattered throughout the central pulp.
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 Viewed
from the side, they appear spindle
shaped.
 They
are believed to be a totipotent cell &
when need arises they may become
odontoblasts, fibroblasts, or macrophages.
 Decrease
in number in old age.
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 The
second most prominent cell in the pulp.
 Reside
adjacent to the predentin with cell bodies in
the pulp & cell processes in the dentinal tubules.
 About
5 to 7 um in diameter & 25 to 40 um in length.
 Cell
bodies are columnar in appearance with large
oval nuclei, which fill the basal part of the cell.
 The
plasma membranes of adjacent cells exhibit
junctional complexes.
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 The
tight & intermediate junctional complexes are
important for maintaining the integrity of the
odontoblastic layer & preventing the ingress of foreign
material, for example toxins & bacterial products, from
the oral cavity.
 The
tight junctions provide mechanical attachment
between adjacent odontoblasts.
 Intermediate junctions have shown to extend around the
perimeter of odontoblasts as narrow bands.
 The
gap junctions are areas of reduced electrical
resistance that also allow selective exchange of
substances between odontoblasts.
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 Near
the pulpal-predentin junction the cell cytoplasm is
devoid of organelles.
 The
process of the cell contains no endoplasmic
reticulum, but during the early period of active
dentinogenesis it does contain occasional mitochondria &
vesicles.
 They
are columnar in the crown & cuboidal in the root.
 Close
to the apex of an adult tooth the odontoblasts are
ovoid & spindle shaped, appearing more like osteoblasts.
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 These
are histiocytes, or macrophages, mast
cells, and plasma cells.
 In
addition,
there
eosinophils, basophils,
monocytes.
are
neutrophils,
lymphocytes, and
 These
cells emigrate from the pulpal blood
vessels & develop characteristics in response
to inflammation.
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 Blood
vessels of both the pulp & periodontium arise
from the inferior or superior alveolar artery.
 As
the vessels enter the tooth their walls become
considerably thinner than those surrounding the
tooth.
 Pulpal
pressure is among the highest of body tissues.
 The
flow of blood in arterioles is 0.3 to 1 mm/s, in
venules 0.15 mm/s , & in capillaries 0.08 mm/s.
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 The
largest arteries in the human pulp are 50 to 100 um
in diameter, thus equaling in size arterioles found in the
most areas of the body.
 Pericytes
are capillary associated fibroblasts, have been
suggested as progenitor cells for replacement of
odontoblasts.
 Veins
& venules measure 100 to 150 um in diameter.
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 Those
draining the anterior teeth pass to the
submental lymph nodes;
 Those
of the posterior teeth pass to
submandibular and deep cervical lymph nodes.
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the
 The
sensory & postganglionic sympathetic nerves that
innervate the dental pulp originate in the trigeminal
& superior cervical ganglion & enter the teeth
through the apical foramen.
 From
the neural receptor in the pulp, the central
process of a trigeminal sensory neuron traverses the
trigeminal ganglion located in the floor of the middle
cranial fossa.
 The
central process then synapses on a second-order
neuron located in the subnucleus caudalis of the
brainstem trigeminal complex.
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 The
majority of second order neurons then decussate &
ascend to synapse on neural cell bodies located on the
ventro postero –medial nucleus of the thalamus.
 The
third order neurons ascend to the area of the postcentral gyrus concerned with the orofacial region.
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 First
order neuron - detects a stimulus and transmits
the signal to the spinal cord or brain stem.
 Second
order neuron -continues to the thalamus at
upper end of brainstem.
 Third
order neuron -carries the signal to the cerebral
cortex.
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 The
majority of the nerves that enter the pulp are
non-myelinated.
 Many of these gain a myelin sheath later in life.
 Are sympathetic in nature.
 Function in vasoconstriction.
 The
large myelinated fibers mediate the sensation of
pain.
 The
peripheral axons form a network of nerves
located adjacent to the cell-rich zone. This is termed
the parietal layer of nerves, also known as the
plexus of Rashkow.
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•
Inductive - To induce oral epithelial differentiation into dental lamina &
enamel organ formation.
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Formative - Produce the dentin that surrounds & protects the pulp.
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Nutritive - Nourishes the dentin through odontoblasts & by means of blood
vascular system.
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Protective -Respond with pain to all stimuli.
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Defensive or reparative - Produce reparative dentin & mineralize any
affected dental tubules.
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CELL CHANGES
 Cells decrease in number.
 Decrease
in size & number of cytoplasmic organelles.
 The
fibroblasts in the aging pulp exhibit less perinuclear
cytoplasm & possess long, thin cytoplasmic processes.
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 Increase
in fibers in the pulp organ is gradual.
 Any external trauma such as dental caries or deep
restoration usually causes a localized fibrosis or
scarring effect.
 Collagen increase is noted in the medial & adventitial
layers of blood vessels as well.
 Decrease in the size of pulp.
 Plaques may appear in pulpal vessels.
 Calcifications in the walls of blood vessels is found
most often in the region near the apical foramen.
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 Are
nodular, calcified masses appearing in either or
both the coronal or root portions of the pulp organ.
 Classified
as true denticles, false denticles, & diffuse
calcifications.
 The
structure of true denticles is similar to dentin.
 Are rare & lie close to the apical foramen.
 Development
of true denticle is caused by the
inclusion of remnants of the epithelial root sheath
within the pulp.
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 Do
not exhibit dentinal tubules.
 Appear
as concentric layers of calcified tissue.
 In
the center, there may be remnants of necrotic &
calcified cells.
 Calcification
of thrombi in blood vessels, called
phleboliths, may also serve as nidi for false denticles.
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Appear as irregular calcific deposits, usually following
collagenous fiber bundles or blood vessels.
•
Are usually found in the root canal & less often in the
coronal area.
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Also classified according to their location in relation to
the surrounding dentinal wall; free, attached, &
embedded denticles.
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The incidence as well as size of pulp stones increase with
age.
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 The
wide pulp chamber in the tooth of a young person
will make a deep cavity preparation hazardous.
 If
opening a pulp chamber for treatment becomes
necessary, its size and variation in shape must be taken
into consideration.
 The
shape of the apical foramen and its location may
play an important part in the treatment of root canals.
 Pulpal-periodontal
lesion due to accessory canals.
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•
When filling materials contain harmful
chemicals (e.g. acid in silicate cements and
monomer in composites), an appropriate
cavity liner should be used prior to the
insertion of restorations.
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The vitality of the pulp depends on its blood
supply. The instruments called vitalometers
test the reaction of the pulp to electrical or
thermal stimuli.
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