The dentin and pulp are considered a complex by its similar embryology and function. It is in our practice to distinguish both by its unique functions it serves in our tooth.
2. CONTENTS
• INTRODUCTION
• THE DENTIN-PULP COMPLEX
• DEVELOPMENT OF THE TOOTH
• THE PULP
• DEVELOPMENT OF PULP
• MORPHOLOGIC ZONES OF PULP
• COMPONENTS OF THE PULP
• PULPAL CALCIFICATIONS
• AGE CHANGES OF THE PULP
3. CONTENTS
• DENTIN
• INTRODUCTION
• STRUCTURE OF DENTIN
• TYPES OF DENTIN
• AGE AND FUNCTIONAL
CHANGES IN DENTIN
• DENTINOGENESIS
• CONCLUSION
• REFERENCES
4. Dentin and pulp are embryologically, histologically, and
functionally the same tissue and therefore are considered as a
complex
Orbans(1980) stated that “The pulp lives for the dentin
and the dentin lives by the grace of the pulp. Few
marriages in nature are marked by a greater
interrelationship. Thus it is with the pulp and the four
functions that it serves: namely, the formation and the
nutrition of dentin and the innervation and defence of the
tooth”
Based on this Nanci (2005)has stated that the pulp and
dentin can no longer be studied as two separate entities
but must be viewed as the pulp-dentin complex.
5. THE DENTIN PULP
COMPLEX
• The dentin and pulp are interlinked to one another both embryologically
and functionally.
• Histologically, it is the practice to distinguish between dentin and pulp.
The former being a hard tissue and the latter, a soft tissue.
• This unity is exemplified by the classic functions of the pulp:
1. Formative (Produces the dentin that surrounds it)
2. Nutritive (Nourishes the avascular dentin)
3. Protective (Innervation to the dentin causing sensitivity)
4. Reparative (Capability of producing new dentin)
6. DEVELOPMENT OF THE TOOTH
Cementum
Tooth germ
Enamel organ Enamel
Dental papilla Dentin
Dental follicle
Pulp
Periodontal ligament
Alveolar bone
7. DEVELOPMENTAL
STAGES
• On the basis of the
enamel organ:
1. Bud stage
2. Cap stage
3. Bell stage
4. Advanced bell stage
8. DEVELOPMENTAL
STAGES
• BUD STAGE
• It is represented by the first
epithelial incursion into the
ectomesenchyme of the jaw.
• As a result of increased
proliferation of ectomesenchymal
cells and migration of neural crest
cells, the cellular density of
ectomesenchyme immediately
adjacent of the enamel organ
increases. This is referred to as
condensation of ectomesenchyme.
9. DEVELOPMENTAL
STAGES
• CAP STAGE
• As the tooth bud grows larger, due to unequal
rate of proliferation, the epithelial outgrowth
superficially resembles a cap sitting on a ball
of condensed ectomesenchyme, referred
widely as dental organ (enamel organ).
• The ball of condensed ectomesenchymal cells,
called the dental papilla, will form the dentin
and pulp.
• The condensed ectomesenchyme limiting the
dental papilla and encapsulating the enamel
organ – the dental follicle or sac- gives rise to
the supporting tissues of the tooth.
10. DEVELOPMENTAL
STAGES
• BELL STAGE
• As the enamel organ further
invaginates with growth in the
margins, it takes the shape of a
bell.
• During this stage, the tooth
crown assumes its final shape
(morphodifferentiation), and the
cells that form the hard tissues
of the crown (ameloblasts and
odontoblasts) acquire
histodifferentition.
11. PULP
The pulp is a soft connective tissue of
mesenchymal origin residing within the pulp
chamber and root canal of teeth (Cohen).
12. ANATOMY OF PULP
Pulp Chamber or coronal
pulp, located in the crown
of the tooth.
Root canal or radicular pulp,
is the portion of the pulp
located in the root area.
The apical foramen is the
opening from the pulp atthe
apex of the tooth.
Accessory canals or lateral
canal, extra canal located on
the lateral portions of the
root.
Pulp horns
13. DEVELOPMENT OF PULP
Begins at the 8th week of embryoniclife.
Inner enamel epithelium
(Signalling molecules)
Dental papilla cells undergoes cytodifferenciation into a peripheral
layer of odontoblasts & central mass of fibroblasts
Once odontoblasts have begun to lay down dentine
Dental papilla becomes dental pulp
14. PERIPHERAL
ZONE
(ODONTOGENIC
ZONE).
MORPHOLOGICAL ZONES OF THE
PULP
Dentin
CENTRALZONE
(PULPCORE)
The coronal pulp when
viewed under the
microscope shows the
following zones:
1. Odontoblastic zone
2. Cell-free zone of
Weil
3. Cell –rich zone
4. Pulp core
15. ODONTOGENIC ZONE
• The presence of odontoblasts in a palisading order.
• Location:Adjacent to the predentin with the cell bodies in
the pulp and cell processes in the dentinal tubules.
• Crowding of odontoblasts present due to the reduction in
surface area when the odontoblasts move inward and
produce the secondary dentin.
Dentin
• Depending on the function, the
odontoblasts may be in active,
transitional or resting phase.
16. CELL FREE ZONE (THE ZONE OF WEIL)
• Appears as a space between the odontoblastic zone and cell-rich
zone.
• Devoid of cells but a few fibers may run through this zone.
• It is suggested to be the area of mobilization and replacement of
odontoblasts.
17. CELL - RICH ZONE
This zone is present beneath the cell-free zone.
It contains numerous cells, fibroblasts being the highest population.
• Fibroblasts – Predominant group of cells in the pulp.
Function: Synthesize and degrade collagen.
The size of the cells decreases as age advances.
• Undifferentiated mesenchymal
cells: Totipotent cells which
differentiate into odontoblasts,
fibroblasts or macrophages.
• Defence cells: Histiocytes,
macrophages, dendritic cells,
mast cells and plasma cells.
Leucocytes also present.
• Fibres: Type I and Type III
collagen fibres
18. PULP CORE
• Contains blood vessels &
nerves embedded in the pulp
matrix with fibroblasts.
• Neurovascular bundles
enter/exit this core through the
apical foramen.
• The nerve bundles branch as
they reach coronal portion and
become extensive and form a
plexus – Plexus of Raschkow.
• Glycosaminoglycans,
glycoproteins and water
constitute the ground substance
of pulp.
20. CELLS OF THE PULP
Macrophages, lymphocytes, eosinophils,
mast cells and plasma cells.
Progenitor cells:
Undifferentiated mesenchymal cells.
2Synthetic cells (formative cells):
Odontoblasts and fibroblasts.
3Defensive cells:
21. PROGENITOR CELLS
UNDIFFERENTIATED
MESENCHYMAL CELLS)
• They are smaller than fibroblasts
but have a similar appearance.
• They are usually found along the walls
of blood vessels.
• These cells have the potentiality of
forming other types of formative or
defensive cells.
22. PROGENITOR CELLS
DENTAL PULP STEM CELLS)
• Mesenchymal stem cells have been isolated from the dental
pulp of adult and deciduous teeth.
• These post-natal dental pulp stem cells have a self-renewal
capability and can differentiate into odontoblasts,
chondroblasts, adipocytes and neurons.
• Capacity to give rise to osteoblasts and may therefore be a
promising tool for bone regeneration.
23. ODONTOBLASTS
• Highly differentiated cell of the pulp.
• Function: Production of dentin
• In the early stages of development
odontoblasts consist of a single layer of
columnar cells.
• In the later stages of development, the
odontoblasts appeared pyriform where the
broadest part of the cell contains the
nucleus.
FORMATIVE CELLS
24. FIBROBLASTS
• These are the most numerous type of
pulp cells particularly in the coronal
portion of the pulp.
• They are spindle in shape.
• They have elongated processes which are
link up with those of other pulpal fibroblasts
(stellate appearance).
• The nucleus stains deep with basic dye
and the cytoplasm is highly stained
and homogenous.
25. These cells have a double function: formation and
degradation of fibers and ground substances.
In young pulp, they are :
*Large cells
*With large multiple processes
*Centrally located oval nucleus,
*Numerous mitochondria,
*Well developed Golgi bodies
*Well developed RER
mitochondria
Fibroblast
protein
secreting cell
26. • In periods of less activity and aging they appear
smaller and round or spindle-shaped with few
organelles, they are termed fibrocytes.
Apoptotic cell death of pulpal fibroblasts, especially
in cell-rich zone , indicates turnover of these cells.
fibrocyte
fibroblast
27. DEFENSIVE CELLS
HISTIOCYTE
(MACROPHAGE):
• They appear irregular in shape with short blunt
processes.
• The nucleus is small, more rounded & darker in
staining than fibroblast.
• They are distributed around the odontoblasts and
small blood vessels and capillaries.
28. In case of inflammation:
*Nuclei increase in size and exhibit a
prominent nucleolus.
*It exhibits granules and vacuoles in their
cytoplasm.
The distinguishing feature of macrophages
is aggregates of vesicles, or
phagosomes, which contain
phagocytized dense irregular bodies.
29. *MACROPHAGES ARE
INVOLVED IN THE
ELIMINATION OF DEAD
CELLS.
*Macrophages remove
bacteria and interact with
other inflammatory cells to
protect the pulp during
inflammation.
30. PLASMACELLS:
• These cells are seen during inflammation.
• The nucleus of this cell is small and appears
concentric in the cytoplasm.
• The arrangement of chromatin in the nucleus
gives the cell a cart wheel appearance.
• The plasma cells are known to produce
antibodies.
31. LYMPHOCYTES
• They are found in normal pulp and
they increase during
inflammation.
• T-lymphocytes are mostly present.
EOSINOPHILS
They are found in normal
pulp and they increase
during inflammation.
32. MAST CELLS:
• They have a round nucleus and their
cytoplasm contains many granules.
• They are demonstrated by using specific
stains as toluidine blue.
• They produce histamine& heparin
.
34. THE GROUND SUBSTANCES
OF THE PULP
• Ground substance, the main constituent of the pulp, is a
part of the matrix that surrounds and supports the cellular
and vascular elements of the pulp.
• The ground substances consists of acid mucopolysaccharides,
water and neutral glycoprotein.
• Glycosaminoglycans are bulky molecules and hydrophilic, they
form gels that fill most of the extracellular space, They
contribute to the high tissue fluid pressure of the pulp.
35. THE GROUND SUBSTANCES
OF THE PULP
Functions:
• Serves as a transport medium for metabolites and waste products
of cells as a barrier against the spread of bacteria.
• These substances are the environment that promotes life of
the cells.
Alterations in composition of the ground substance caused by
age or disease interfere with this function, producing metabolic
changes, reduced cellular function, and irregularities in mineral
deposition.
36. CONNECTIVE TISSUE FIBRES OF
THE DENTAL PULP
Three types of fibres are found in the connective tissue:
• Collagenous
• Reticular
• Elastic
37. COLLAGEN FIBRES
Mainly collagen fibre are type I
and type III.
These fibers form a loose,
reticular network to
support other structural
elements of the pulp.
Collagen is synthesized and
secreted by odontoblasts and
fibroblasts.
Greatest concentration present
in apical portion of the pulp
38. COLLAGEN FIBRES
In young pulp the fibers are relatively sparse throughout the
pulp & gradually the bundles increase in size with advancing
age.
In dentin, the matrix in which mineralization occurs is
composed of collagen fibrils and glycosaminoglycans which
has a tendency to attract minerals.
39. RETICULAR FIBRES
Reticular fibres are found in connective tissue early in
development.
They persist in the gingiva and dental pulp.
The von Kroff fibres are immature collagen fibrils and ground
substance found coursing from pulp through the odontoblastic
layer into the predentin.
ELASTIC FIBRES
Elastic fibres are produced by fibroblasts.
Elastic fibres are not found in the dental pulp but are present in
the alveolar mucosa and submucosa.
40. BLOOD VESSELS
• The pulp is highly vascularized. It
is supplied by the:
i. Inferior and superior alveolar
arteries & also drain by the same
veins
ii. Infraorbital
iii. Inferior alveolar branches of the
internal maxillary artery
*
41.
42. BLOOD VESSELS
• A single artery or several
smaller arteries enter the
pulps through apical
foramen or foramina.
• Smaller vessels enter
through lateral and
accessory foramina.
• The pulpal veins
together with other
venous tributaries, form
the pterygoid plexus
located posterior to the
maxillary tuberosity.
43. REGULATION OF PULPAL
BLOOD FLOW
• Walls of arterioles and
venules are associated with
smooth muscles which are
innervated by unmyelinated
sympathetic fibres.
• When stimulated by
stimulus (e.g. epinephrine
containing local
anaesthetics), muscle fibers
contract, decreasing the
blood supply.
44. REGULATION OF PULPAL
BLOOD FLOW
• The pulpal blood flow mainly determines the speed of
diffusion between the blood and the interstitial fluid; higher
the blood flow, the faster the diffusion.
• Regulation of an adequate blood flow is a crucial point for
survival and normal function in any tissue.
FUNCTIONS:
• Transport nutrients, fluids, and oxygen to the tissues and to
remove metabolic waste from the tissues by maintaining an
adequate blood flow through the capillaries.
• The transfer of nutrients and metabolic wastes through the
capillary walls is controlled by the law of hydrostatics and
osmosis.
45. LYMPHATIC DRAINAGE OF
THE PULP
• Lymphatic vessels also occur in the pulpal
tissue.
• Small, blind, thin-walled vessels in the
coronal region of the pulp and pass apically
through the middle and radicular regions of
the pulp to exit via one or two larger
vessels through the apical foramen.
FUNCTION:
• Removal of interstitial fluid and metabolic
waste products to maintain the intrapulpal
tissue pressure at normal level.
• Average intrapulpal pressure is
approximately 10 mmHg.
46. NERVES OF THE PULP
• The pulp has an abundant
nerve supply which follows
the distribution of the blood
vessels.
• The sensory mechanism of
the pulp is composed of:
• Sensory afferent
• Autonomic efferent
47. The afferent system conducts impulses perceived by the pulp from a
variety of stimuli to the cortex of the brain, where they are
interpreted as pain, regardless of the stimulus.
Stimulated impulse travels from C or A-delta fiber nerve endings
The plexus of Raschkow
Nerve trunk in the central zone of the pulp
that exits the tooth through apical foramen
Pons
Thalamus
Cortex
48. The efferent motor pathway in the dental
pulp consists of sympathetic fibres from the
cervical ganglion that enter through the
apical foramina in the outer layer of the
arterioles, the tunica adventitia.
The sympathetic nerves provide vasomotor
control to circulation and therefore regulate
the blood flow and intrapulpal blood pressure
in response to stimuli.
49. A-delta fibers
• Conduction velocity 2-30 m/s
• Lower threshold
• Involved in fast, sharp pain
• Stimulated by hydrodynamic
stimuli
• Sensitive to ischemia
C fibers
Conduction velocity 0-2 m/s
Higher threshold
Involved in slow, dull pain
Stimulated by direct pulp
damage
Sensitive to anesthetics
Dull pain
TYPES AND PROPERTIES OF PULPAL SENSORY
NERVE FIBERS
A-beta fibers
Conduction velocity 30-70 m/s
Very low threshold, non-
noxious sensation
50% of myelinated fibers in
pulp
Functions not fully known
Non-myelinated sympathetic
fibers
Conduction velocity 0-2 m/s
Post-ganglionic fibers of
superior cervical ganglion
Vasoconstriction
50.
51. • More nerve endings are found in the pulp horns than in other
peripheral areas of the coronal or radicular pulp.
• As the mylelinated nerves run coronally, they give off side branches
and lose their myelin coat & form then sub-odontoblastic plexus of
nerves known as plexus of Rashkow. Few axons extend in-between
the odontoblasts to give the nerve endings.
52. PULPAL CALCIFICATIONS
Pulp stones, also known as denticles, are calcifies, nodular
structures seen in coronal or radicular pulp, more commonly
in the coronal pulp.
They are discrete calcified masses that have calcium-
phosphorus ratios comparable to that of dentin.
Singular or multiple in any tooth and are found frequently at
the orifice of the pulp chamber or within the root canal.
Histologically, they usually consist of concentric layers of
mineralized tissue formed by surface accretion around blood
thrombi, dying or dead cells, or collagen fibers.
53. PATHOGENESIS OF PULP CALCIFICATIONS
LOCAL METABOLIC
DYSFUNCTION TRAUMA
HYALINISATION OF
INJURED CELLS
VASCULAR
DAMAGE
(thrombosis)
FIBROSIS
MINERALISATION
(nidus formation)
PULP STONES
GROWTH
WITH TIME
55. TRUEDENTICLES
• Rare
• Small in size.
• Found near the apical foramen
• They consist of irregular dentin
containing traces of dentinal
tubules and few odontoblasts.
• Remnants of the epithelial root
sheath invade the pulp tissues
causing UMC of the pulp to
form this irregular type of
dentin.
FALSE DENTICLES
•Evidence of dystrophic
calcification of the pulp tissue .
•No dentinal tubules & can exist in any
area of
the pulp.
•Formed of degenerated cells or
areas of hemorrhage which act as a
central nidus for calcification.
•Overdoses of vit. D, may favor the
formation of numerous denticles.
56. DIFFUSE PULP
CALCIFICATION
Commonly occurs on top of hyaline degeneration in the root canal
and not common in the pulp chamber.
They are irregular calcific deposition in the pulp tissue following the
course of blood vessels or collagenous bundle.
Advancing age favors their development.
Calcifications in the root canals are usually are not seen
radiographically, but are detectable during exploration of the root canal.
This type of calcification may prevent the clinician from reaching
apical foramen and may therefore prevent complete instrumentation of
the root canal.
57. AGE CHANGES IN THE PULP
• That the pulp
supports the dentin
and that age changes
within the pulp are
reflected in the
dentin.
• The ability of the
pulp-dentin complex
to repair itself lessens
as age advances due
to decreased cellular
metabolism.
58. AGE CHANGES IN THE PULP
The size of the pulp
The apical foramen
The cellular elements
The bloodvessels &
nerves
Vitality
.
Decreased
59. AGE CHANGES IN THE PULP
• Reduction in size and volume of pulp chamber:
Continuous deposition of secondary dentin and
the deposition of reparative dentin in response
to stimuli reduces the size of the pulp chambers
and root canals and root canals thereby
decreases the pulp volume.
• The diminution of the pulp is called atrophy.
• Complete obliteration of the root canal occurs
in old teeth as a result of which the vascular
supply decreases. Such teeth may become
brittle and fracture easily.
60. AGE CHANGES IN THE PULP
• Decrease in diameter of the dentinal
tubules by the continuous deposition of
peritubular dentin also occurs.
• Some of these tubules close completely
and form sclerotic dentin. The decrease
in pulp volume reduces cellular,
vascular, and neural content of the pulp.
The odontoblasts undergo atrophy and
may disappear completely under areas of
sclerotic dentin.
• Reduction in the fluid content of the
dentinal tubules is also seen. These
changes make the dentin less permeable
and more resistant to external stimuli.
61. AGE CHANGES IN THE PULP
• Reduction in cell number: The cell population of the pulp
chamber as well as the root canal decreases with age. The
intracellular organelles also decrease in number.
• Changes in collagenous elements:
• Fibroblasts are reduced in size and numbers, but the collagen
fibres are increased in number and size. This is due to the
decrease in collagen solubility and turnover with advancing age.
This change is referred to as fibrosis.
• Fibrosis is more evident in radicular pulp. Fibrosis around the
capillaries and the blood vessels also takes place as age advances.
62. AGE CHANGES IN THE PULP
• Changes in the blood vessels: Atherosclerotic plaque formation is
seen on the vessel walls of the pulp tissue.
• Changes in the nerve distribution: Degeneration of myelinated
and non-myelinated axons takes place as age advances. This leads
to decreased sensitivity.
• Dystrophic calcifications: May be seen in relation to the blood
vessels or the collagen bundles. Commonly seen in root canals.
63. DENTIN
• Hard tissue portion of the
pulp- dentin complex the
bulk of the tooth
• First formed
• Formation begins in late bell
stage
• Formed by odontoblasts
• Bound to enamel at DEJ & to
cementum at CEJ
• Consists of large no of small
parallel tubules in a
mineralized collagen matrix.
• Vital, non-living
64. STRUCTURE OF
DENTIN
DENTINAL TUBULES
• Dentin is permeated by dentinal tubules.
• It runs from pulpal surface to DEJ & CEJ.
• tubules indicates the course taken by the odontoblasts during
dentinogenesis.
PRIMARY CURVATURE
• Tubules follow an S- shaped path
• results from the crowding of & path followed by odontoblasts as
they move towards the centre of the pulp.
• First curve towards apex, second towards crown
• In root dentin- little or no crowding- tubules run in a straight
course
66. Secondary curvatures:
Tubules also show changes in direction of smaller amplitude(a
few micrometers), observed under higher magnification.
67. Terminal branches:
• more profuse in root dentin than in coronal dentin.
• show a Yshaped terminalbranching.
Lateral branches:
• tubules show lateral branches , almost 45 degree to
main tubule, may contain O. Process, may
communicate with adjacent ones or blindly end in
intertubular dentin.
TUBULE POPULATION:
Approx;
20000/mm² – towards DEJ
30000/mm²-75000/mm² – towards the pulp
• Dentinal tubules are tapered shape
• larger near pulp- 2.5 µm in diameter
• smaller at DEJ- 1 µm or less
71. PRIMARY DENTIN
•Formed before root completion
•Consists of mantle dentine and circumpulpal dentin
1) MANTLE DENTINE
• First formed dentin in crown
• Underlying the DEJ
• 20 µm thick
• Fibrils are perpendicular to DEJ
• Organic matrix – von korffs fibres (large diameter fibrils-
type III collagen fibrils)
• Less mineralized compared to circumpulpal dentin.
• Matrix vesicles involved in mineralization.
• Globular mineralization
72. PRIMARY DENTIN
2) CIRCUMPULPAL DENTIN:
• Forms the remaining primary dentin or bulk of the tooth.
• The fibrils are much smaller in diameter (0.05micrometer)
& are more closely packed together.
• Slightly more mineral content than mantle dentin.
73. SECONDARY DENTIN
• Narrow band of dentin bordering the pulp.
• Forms after root formation is complete.
• It is a slow continous deposition of dentin.
• Contains fewer tubules than primary dentin.
• It is formed more slowly than primary dentin.
• Secondary dentin is not formed uniformly and
appears in great amounts on the roof and floor of
coronal pulp chamber, where it protects the pulp from
exposure.
74. TERITIARY DENTIN
• Reactive, Reparative, Irregular dentin.
• Produced in reaction to various stimuli such as attrition,
caries or restorative procedure.
• Quality and quantity depends on intensity and duration of
stimulus.
• Tubules may or may not be present.
75. STIMULI
ODONTOBLASTS DIE FEW ODONTOBLAST
SURVIVE
MIGRATION OF
UNDIFFERENCIATED
CELLS FROM PULPTO
DENTIN
REPARATIVE DENTIN REACTIONARY DENTIN
76. TERTIARY DENTIN
REPARATIVE
DENTIN
• Formed by the newly
differentiated odontoblast-like
cells that replace the original
odontoblasts that have been
destroyed by insult/stimulus.
• Irregular and fewer and more
tubules.
• Normally, odontoblasts move
away from the matrix they
form (tubular dentin), but the
newly differentiated
odontoblast-like cells may get
entrapped in the matrix they
form to produce osteodentin.
REACTIONARY
DENTIN
• Formed by the existing
odontoblasts which have
survived severe damage
caused to them by
insult/stimulus.
• Irregular appearance with
fewer tubules.
77. Types Of Reparative Dentin
Atubular dentin ( area
without dentinal tubules)
Osteodentin (entrapped cells).
Vasodentin
(entrapped b.v.)
78. PERITUBULAR
DENTIN
• Wall of dentinal tubules
• Highly mineralised
• Lost during decalcification
Other name: INTRATUBULAR
DENTIN
• Deposition of the minerals occurs in the
inner wall of the tubule rather on the
outer wall, the term intratubular dentin
is considered more appropriate.
• 15% more mineralized
than intertubular dentin
• Lacks collagenous
fibrous matrix.
79. INTERTUBULAR
DENTIN
• Located between the dentinal
tubules.
• The primary end product of the
odontoblasts.
• Fibrils are arranged at roughly
right angles to the DT.
• FIBRILS 0.5 – 0.2
micrometres in diameter.
• Less calcified
• Bulk of dentin
• Retained after decalcification
81. PREDENTIN
• The newly laid, yet–to-be mineralized
dentin matrix.
• Located adjacent to the pulp tissue.
• It is the mineralising front of the dentin.
• 2 to 6 microns thick, depending on the
activity of the odontoblast.
• The predentin appears to be pale staining
than the mineralized dentin owing to
differences in composition of the matrix.
82. INTERGLOBULAR
DENTIN
• Areas of hypomineralized dentin
where globular zones of
mineralization (calcosperites) have
failed to fuse into a homogenous
mass within mature dentin.
• Seen in the circumpulpal dentin just
below the mantle dentin.
• The dentinal tubules pass
uninterruptedly, thus demonstrating a
defect of mineralization & not of
matrix formation.
• Appear dark in transmitted light &
bright under reflected light- ground
sections.
83. TOMES’ GRANULAR LAYER:
• In root dentin adjacent to CDJ, when viewed
under transmitted light in ground sections a
granular layer can be seen.
• Caused by coalescing and looping of the
terminal portions of the dentinal tubules.
• The air spaces thus created appear dark and
granular in ground sections because of
internal reflection of transmitted light.
HYALINE LAYER:
• Outside the granular layer is a clear hyaline
layer.
• Upto 20 µm wide
• Usually included as a component of the
dentin.
• May serve to bond cementum to dentin.
84. STRUCTURAL LINES IN DENTIN
There are 2 groups of lines:
(1) Lines associated with primary and secondary
curvature of dentinal tubules.
(a) Schreger lines (primary curvature)
(b) Contour lines of owen (secondary curvature)
(2) Lines arising from the incremental deposition of dentin
and its subsequent mineralization.
(a) Incremental lines of von ebner (short period lines)
(b) Andersons line (long period lines)
85. CONTOUR LINES OF OWEN:
• Coincidence of the secondary curvatures
between the neighbouring dentinal
tubules.
• Some of the incremental lines are
accentuated because of disturbances in
the matrix and mineralization process.
• Seen in ground sections as
hypocalcified bands.
NEONATALLINE:
• Represents an exxagerated contour line of
owen & shows the changes in physiology
(nutritional, hormonal, etc.) that occur at
birth.
• Seen in primary teeth & the first permanent
molars.
• Dentine distal to this line (nearer to DEJ) -
formed prior to birth & the dentine proximal to
it(nearer to the pulp - formed after birth.
86. INCREMENTAL LINES (VON EBNER), OR
IMBRICATION LINES OR SHORT
PERIOD LINE
Appear as fine lines or striations in dentin.
Seen as alternating dark & light bands.
Run at right angles to the dentinal tubules.
Reflect the diurnal rhythm of dentin deposition as well
as hesitation in the daily formative process.
Cuspal dentin -4µm/day(rapid deposition)
Root dentine - 2µm/day(slower)
ANDERSONS LINES (LONG PERIOD
LINES)
The term long period refers to the intrinsic
temporal repeatinterval that is greater than one
day (in contrast to daily short periodline).
16 - 20µm apart
Between each long period line there are 6 – 10
pairs of short period lines.
Cause for the 6 to 10 day periodicity is
unknown.
87. AGE AND FUNCTIONAL
CHANGES IN DENTIN
1. VITALITY OFDENTIN:
• Odontoblasts & its processes are an integral part of dentin.
• Reacts to physiologic and pathologic stimuli.
• As age advances, the ability of dentin to respond to stimuli
decreases.
2. SECONDARY DENTIN:
• Continuous deposition of secondary dentin leads to the
decrease in the size of the pulp cavity & obliteration of
the pulp horns with narrow root canal to protect pulp
from exposure.
88. AGE AND FUNCTIONAL
CHANGES IN DENTIN
3. TERITIARY DENTIN:
• It is formed only by cells directly affected by the stimulus
and depends on the intensity and duration of stimulus.
4. TRANSLUCENT DENTIN:
• As a result of physiologic ageing, dentinal tubules become
completely occluded with apatite crystals, especially in the
roots.
• Formation starts at the root apex and proceeds cervically
with age.
• Used in forensic dentistry to estimate the age of the tooth.
89. 5. SCLEROTIC DENTIN:
• Dentinal tubules become
occluded with calcified material
in response to external stimuli.
• When this occurs in several tubules
the dentin assumes a glassy
appearance.
• Found specially in radicular
dentin (apical 3rd).
• Transparent or light in transmitted
and dark in reflected light.
• Sclerotic dentin is harder, has
reduced fracture toughness but same
elastic properties as normal dentin.
90. 5. DEAD
TRACTS
Tubules affected by caries may
fill with bacteria
Odontoblast processes
may disintegrate or retract
Leaving behind an empty
space-dead tract
• In ground sections appear black
in transmitted light because they
entrap air.
• Seen more commonly in older
teeth and demonstrate reduced
sensitivity.
91. DENTAL PAPILLA CELLS (LATE
BELL STAGE)
CYTODIFFERENCIATION OF
ODONTOBLASTS
DEPOSITION OF ORGANIC MATRIX
MANTLE PREDENTINAPPEARS
MINERALIZATION PHASE
CIRCUMPULPAL DENTIN(PRIMARY
DENTIN)
ROOT DENTIN
SECONDARY DENTIN
DENTINOGENESIS
1. Odontoblast
Differentiation
2. Matrix Formation
3. Good Vascular Supply
4. Mineralization
92.
93.
94. DENTINOGENESIS
Dentin formation begins when the tooth germ has reached
bell-stage of development.
Under the influence of inner enamel epithelium, the
outermost ectomesenchymal cells of dental papilla
differentiate into odontoblasts.
Initially, the cells of the dental papilla are small,
undifferentiated and have few organelles.
Inner enamel epithelium releases transforming growth
factor, insulin growth factor and bone morphogenetic
protein for the differentiation of odontoblasts.
Differentiation begins adjacent to the deepest invagination
of the enamel organ, the portion of the future cusp tip.
95. DENTINOGENESIS
The cells of dental papilla immediately adjoining the
acellular zone enlarge to become preodontoblasts, which
change their shape from ovoid to columnar and differentiate
into odontoblasts.
The nucleus is oriented towards the base (away from the
inner enamel epithelium) and increased amounts of protein-
synthesizing organelles appear in cytoplasm.
97. Odontoblast become a protein forming and secreting cell.
• R E R , Mitochondria and Golgi bodies
• Ribonucleic acid and alkaline phosphatase
Inner dental
Predentin
Epithelial
side
Large open
faced nucleus
R E R
Mitochondria
Golgi
bodies
98. MATRIX FORMATION
• A- Mantle dentin
• The first formed dentin
layer in crown
• And root
Fibers are perpendicular to
D E J
Fibers are parallel to
basement membrane
99. Mantle dentin
Circumpulpal
dentin. The fibers
are parallel to DEJ (
right or oblique
angle to DT)
Crowding of the
cells and
appearance of
junctional complex
100. MATRIX FORMATION
Dentinogenesis occurs in a two-phase sequence.
Collagen matrix is formed first and then calcified.
Matrix formation begins with the appearance of large
diameter collagen fibrils (0.1-0.2 micrometres) known as
Vonkroff’s fibres.
These fibres are laid down at right angles to the future DEJ.
Once the mantle dentin is laid, the remaining collagen fibres
are laid parallel to the DEJ.
As the odontoblast forms the matrix and move towards the
pulp, several fibres join to form the processes that are
embedded in the dentinal tubules.
101. MATRIX FORMATION
Dentin is formed at a rate of about 4 micrometres/day till the
crow is formed and the tooth erupts.
As each increment of the matrix is formed, it remains for a
day before it is calcified and the next increment of the
matrix forms.
The rate of matrix formation is slower in the radicular dentin
and it contains collagen fibres which is parallel to the CEJ.
102. MINERALIZATION
As the odontoblasts give off processes, they also bud off
several membrane-bound vesicles called matrix vesicles,
which are involved in the mineralization of the mantle
dentin.
These vesicles contain the enzyme alkaline phosphatase,
which increases the concentration of phosphates. The
phosphate combines with calcium to form apatite.
These apatite crystals grow and rupture from the confines of
the vesicles to form a cluster of crystallites which fuses with
adjacent clusters to form a continuous layer of mineralized
matrix.
103. • Several proteins are released to regulate the deposition of minerals.
•DPP (Dentin phosphoproteins) concentration elevated - inhibits
mineralization
• OSTEONECTIN – it can inhibit hydroxyapatite crystals growth
& promote Calcium & phosphorous binding to collagen
• OSTEOPONTIN – promotes mineralization
• CHONDROITIN SULPHATE – properties vary depending
on whether they are in:
•PREDENTIN - prevent transport anddiffusion of
crystals(inhibitors)
MINERALIZING DENTIN -promote hydroxyapatite crystal
formation.
104. MINERALIZATION PATTERN
Histologically 2 mineralization patterns seen depending on the rate of
dentin formation:
1. Globular calcification
2. Linear calcification
Globular calcification
• Deposition of crystals in discrete areas of matrix by
heterogeneous capture in collagen.
• Globules enlarge & eventually fuse to form single calcifiedmass.
• Seen in mantle dentin formation
Linear calcification
• Rate of formation slow- mineralization front apperas
more uniform
• The process is said to be linear.
• Example-circumpulpal dentin
105. MINERALIZATION
Budding of
matrix vesicles Rupture of matrix
vesicles
Mineralization of the
mantle dentin
Has
membrane
rich in
alkaline
phosphatase
Calcium and
phosphate ions
undergo
crystallization
Matrix
vesicle
106. ROOT DENTIN
DEVELOPMENT
• Initiated by HERS
• Space between initial
collagen fibres & HERS
become filled with an
amorphous ground
substance with fibrillar
non collagenous matrix
secreated by root
sheath(10µm).
• Collagen fibres laid down
parallel to CEJ.
107. CONCLUSION
The dentin and pulp are embryologically,
histologically, and functionally similar tissues, and
are considered together as a complex. The vitality of
the dentin-pulp complex is essential to maintaining a
functional viable tooth.
108. REFERENCES
Orban’s Oral Histology and Embryology (14th
Edition)
Seltzer’s The Dental Pulp (3rd Edition)
Ten Cate’s Oral Histology (8th Edition)
Sturdevant’s Art and Science of Operative
Dentistry (South Asian Edition)
Grossman’s Endodontic Practice (12th Edition)
