The dental pulp contains zones including the odontoblastic zone, cell-free zone, and cell-rich zone. Principal cells include odontoblasts that synthesize dentin, fibroblasts that form the pulp matrix, and immune cells. Blood vessels enter the pulp and branches form capillaries. Nerves form the Raschkow plexus near the odontoblasts. The pulp provides nutrients and sensation to the tooth.

1. Histology Of Pulp
Aurelian Jovita Alexander
MDS I Year
Dept Of. Oral and Maxillofacial Pathology

2. Content
• Definition
• Zones of Pulp
• Principal Cells of Pulp
• Collagen Synthesis
• Pulp Calcifications
• Age Changes in Pulp

3. • The dental pulp is the soft connective tissue of
the tooth that supports the dentin.
Definition

4. Zones Of Pulp
• The odontoblastic zone at the pulp periphery
• A Cell- Free Zone of Weil beneath the
odontoblasts
• A Cell- Rich Zone
• Pulp Core

5. Dentin
Predentin
Odontoblasts Layer
Cell rich Zone
Cell free Zone
Pulp Proper

6. Odontoblasts
• The outermost(pulp)
• located immediately subjacent to the predentin;
• Pass through the predentin into the dentin

7. Cell Free Zone
• Immediately subjacent to the odontoblast layer
in the coronal pulp.
• width 40 μm
• Free of cells
• It is traversed by blood capillaries,
unmyelinated nerve fibers, and fibroblasts.

8. Function
• In this space, the odontoblast may move
pulpward during tooth development and later to
limited extent in funtioning teeth.

9. Cell Rich Zone
- Include number of macrophages, dendritic cells
and undifferentiated mesenchymal or stem cells.

10. Pulp Proper
• The pulp proper is the central mass of the pulp.
• The connective tissue cells consist of fibroblasts
or pulpal cells

11. Principal Cells of the Pulp
• Odontoblasts
• Fibroblasts
• Undifferentiated Ectomesenchymal cells
• Macrophages
• Other Immunocompetent Cells

12. Odontoblasts

13. • Most distinctive cells of the dental pulp.
• No. Of Odontoblasts corresponds to No. of
dentinal tubules.
• 59000- 76000 per square millimeter in coronal
dentin. Less in root dentin.
• In fully developed teeth,
Region Shape and size
Crown Of the Pulp Columnar , 50µm in height
Midportion Of the Pulp Cuboidal
Apical Portion Of the Pulp Flattened

14. Columnar
Flattened
Cuboidal

16. Elongated
Basal Nucleus
Basophilic cytoplasm
Prominent Golgi Zone

17. • 3 Stages
- Secretory Stage
- Transitional Stage
- Resting Stage

18. Secretory Phase
• The organelles of an active odontoblasts are
prominent consisting
- Numerous Vesicles
- Much Endoplasmic Reticulum
- Well developed Golgi Complex located on
dentinal side of nucleus
- Numerous Mitochondria
- Nucleus- periphally dispersed chromatin &
several nucleoli

19. Electron micrograph showing the
Golgi region of a secretory
odontoblast in which well-developed
synthesis organelles such as
cisternae of rough endoplasmic
reticulum (RER), Golgi stacks (G),
and secretory granules (g) are
abundant. M, mitochondria
(32,500×).

20. Transitional Phase
• Narrower cell
• Nucleus displaced from the basal extremity
• Condensed Chromatin
• Reduced ER
• Autophagic Vacuoles are present and ass. with
reorganisation of cytoplasm.

21. Resting Or Aged Phase
• Nucleus situatated more apically, creating a
prominent infranuclear region
• Fewer cytoplasmic organelles clustered
• Supranuclear region devoid of organelles
• Large lipid filled vacuoles containing tubular
and filamentous structures.

23. Couve E , and Schmachtenberg O J
DENT RES 2011;90:523-528

24. Cont.
• Synthesizes :
• Mainly Type I Collagen
• Small amounts of - Type V proteoglycans
-Sialoprotein
-Phosphophoryn
- Alkaline Phosphatase

25. Odontoblast Process
• The odontoblast process occupies most of the
space within the tubule and coordinates the
formation of peritubular dentin.
• The process is limited to the inner third of
dentin.
( Garberoglio R, Brännström M: 1976)
• Extending further into the tubule, often as far as
the DEJ.
(Kelley et al,1981) (Grossman et al,1983)
• Extends throughout the entire thickness of
dentin
(Sigal et al,1984)

27. Electron micrograph showing the mineralized
dentine/predentine/odontoblast layer interface.
An odontoblasts processes (P) that arises from
the odontoblast cell body (O) crosses the entire
predentine and penetrates into a tubule of the
mineralized dentine. Some branches (double
arrowheads) of the odontoblast processes are
clearly observed in other odontoblast process
(5400×).

28. Junction between Odontoblasts
• Gap Junctions
• Tight Junctions
• Desmosomes

30. Fibroblasts

32. • Occuring in greatest numbers.
• Numerous in coronal portion of the pulp.
• They appear to be tissue-specific cells that are capable of
giving rise to cells that are committed to differentiation
• (e.g., odontoblast-like cells) if given the proper signal.
• Synthesize types I and III collagen and proteoglycan
Function
Form and maintain Pulp matrix
that consists Collagen and
Ground substance

33. • They produce and maintain the matrix proteins .
• Mitotic activity preceding the differentiation of
replacement odontoblasts appears to occur
primarily among perivascular fibroblasts.
(Especially in dentinal bridge formation after pulpotomy or
exposure)
(Fitzgerald et al,1990)

34. Images captured by a confocal microscope
(representative bars: 20 µm).

35. Macrophages

36. • Monocytes that have left the bloodstream, enters
the tissues, and differentiate into various
subpopulations.
• It plays in phagocytic activity.
• Macrophages participate in immune reactions by
processing antigen and presenting it to memory
T cells.
• In inflammatory stimuli, it produces a large
variety of factors, including interleukin-1, tumor
necrosis factor, growth factors, and other
cytokines

37. Dendritic Cells

38. • Accessory cells of the immune system
• Bone marrow derived
• characterized by:
-dendritic cytoplasmic processes
-presence of cell surface class II antigens

39. Functions
• Are termed
antigen-
presenting cells
• They act as
antigen-
presenting cells
that are
essential for the
induction of
helper T cell
dependent
immunity.
It engulf protein antigens and then
present an assembly of peptide
fragments of the antigens and class
II molecules

40. Undifferentiated Mesenchymal Cells
• Polyhedral in shape.
• Have peripheral processes and large oval
staining nuclei.
• Totipotent cells
• May become formation of odontoblasts,
fibroblasts and macrophages.

41. Lymphocyte
• (Hahn et al,1989) found T lymphocytes in
normal pulps from human teeth.
• Lymphocytes have also been observed in the
pulps of impacted teeth.
(Langeland et al,1965)

42. Mast Cells

43. The granules contain heparin,
an anticoagulant, histamine,
other chemical factors which
release and cause
Inflam. & attack to harmful
substance.

46. Metabolism
• (Yu CY et al,2002) reported that:
* odontoblasts consumed O2 at the rate of 3.2 ±
0.2ml/min/100 g of pulp tissue..
• It is higher during dentinogenesis than after crown
development
• Dental materials ?inhibit oxygen consumption by
pulp tissue as they depress the metabolic activity of
pulpal cells.
(Fisher et al,1957 (Jones et al,1979)
• Orthodontic force? causes changes in respiratory activity of
the pulp.
(Hamersky et al,1980)

47. Ground Substance
• An amorphous , gel like, polyanionic
polysaccharides matrix with water holding
properties where C.T cells and fibers are
embeded
• Nearly all proteins of are glycoproteins.

48. Role of GROUND SUBSTANCE:
Forms a cushion capable of protecting cells and
vascular components. (especialy in young pt,the water pulp is
hight)
It acts as a sieve passage of nutrients , between
cells and blood.
Regulate osmotic pressure by excluding
osmotically active molecules.

49. Connective Tissue Fibres Of Pulp
Two types of structural proteins:
A- ELASTIN: fibers are confined to the walls of
arterioles.
B- COLLAGEN
tropocollagen

51. Found In..
I skin, tendon, bone, dentin, and pulp
II cartilage.
III unmineralized connective tissues
IV component of basement membranes
V a constituent of interstitial tissues
VI widely distributed in low concentrations in
soft tissues at interfibrillar filaments.
VII component of basement membranes

52. Collagen Synthesis
• Type I collagen is synthesized by odontoblasts
and osteoblasts
• Fibroblasts synthesize types I, III, V, and VII
collagen.

54. mRna
Specific AA into Polypeptide Chains on Ribosomes ass. With
RER in Cytoplasm
Amino Acid In Nuclues
Lumen of the RER
Hydroxylation of
Proline and Lysine
Residues- permits
hydrogen bonding
Prolylhydroxylase
Lysylhydroxylase
Glycosylation of some
hydroxylysine residues,
Addition of galactose
galactosyltransferase

55. 3 polypeptide chains assembled in triple helix
Disulfide bonding at C- terminal extension,
catalysed by protien disulfide isomerase
Proper allignment of the chain
Transported to Golgi Complex , Glycosylation completes
Secretory granules containing the procollagen
molecules are formed at the trans face of Golgi Complex
Addition of glusoce to O- linked galactose residues
Exocytosis
at cell
surface

56. The formation of typical banded collgen fibrils ocurs extracellularly
C and N proteinases
The C-terminal and part of N- terminal extensions are removed in the secretory granules
Secreted into extra cellular matrix
Oxidation of lysin and hydroxylysin
=
Final collagen- short end diameter
Lysyloxidase
Short Collagen Fibrils-parrallel,and into the gaps hydroxyapatite crystals get lodged

57. Blood Vessels
• Arise from inferior or superior alveolar artery.
• Drain by the same veins.
• Infection spread through the communication.

58. Arteries
• Small arteries give off numerous branches in
radicular pulp
• Largest arteries- 50-100µm in diameter.
• Pulpal blood flow rapid & pulpal blood pressure
Blood flow in arteries: 0.3 -1 mm/sec
Blood flow in veins : 0.15 mm/ sec
Blood flow in capillaries: 0.08mm/sec

59. • These vessels contain 3 layers
Tunica Intima Tunica media Tunica Adventitia

61. • Tunica intima
– squamous or cuboid endothelial cells
surrounded by closely associated basal lamina.
• Tunica media
– 5µm thick. Consists 1-3 layers of smooth
muscle cells.
A basal lamina surrounds and passes between
these muscle cells and seperates them from
intima.
Occasionally endothelial cell wall is in contact
with muscle cells- MYOENDOTHELIAL
JUNCTION.

62. Tunica adventitia
– made up of few collagen fibres forming a
loose network around the large arteries.

64. Arterioles
• 20-30µm in diameter
• 1-2 layers of smooth muscle cells common
throughout the dental pulp.
• Tunica adventitia blends with the fibres of
surrounding intercellular tissue.

66. Terminal Arterioles
• 10-15µm in diameter, peripherally in the pulp.
• Endothelial cells contain numerous
micropinocytotic vesicles- which function in
transendothelial fluid movement.
• Single layer of smooth muscle cells found.
Occasionally a fibroblast or pericyte lies on the
surface of the vessels.

67. Precapillaries
• Smaller diameter arterioles.
• Slightly larger than the terminal capillaries.
• Exhibit a complete or incomplete single layer of
muscle cells surrounding endothelial lining. 8-
12µm in diameter.

68. Veins and Venules
-Larger than arteries.
-Appear in central region of the root pulp.
-100-150µm in diameter.
-Walls- less regular than those of arteries because of
bends and irregularities along their course,
and thinner in relation to the size of lumen.
Endothelial cells- more flattened and cytoplasm
does not project into the lumen. Fewer
intracytoplasmic filaments.

69. -Tunica media:
1-2 layers of thin smooth muscle cells that
wrap around endothelial cells, and appear
discontinuous or absent in smaller venules.
-Basement membrane: thin and less distinct.
-Tunica Adventitia:
lacking or appears as fibroblasts and fibres
continuous with surrounding pulp tissue.

71. Capillaries
• Appear as endothelium lined tubes, 8-10µm in
diameter.
• Nuclei: lobulated and have cytoplasmic projections
into the luminal surface.
• Few peripheral capillaries found among the
odontoblasts have fenestrations in endothelial cells
– involved in rapid transport of metabolites during
time of dentinal matrix formation and calcification
by the active odontoblasts.

72. • Both fenestrated and continuous terminal capillaries
are found in the odontogenic region.
• During active odontogenesis, capillaries appear
among the odontoblasts adjacent to the predentin.

74. Lymph Vessels
• Endothelium lined tubes
• Join the thin walled lymph venules or veins in
the central pulp
• Thin walls
• Larger vessels have an irregular-shaped lumen
composed of endothelial cells surrounded by an
incomplete layer of pericytes or smooth muscle
cells or both.
• Cells contain multivesicular structures, Weibel
Palade bodies and paracrystalline inclusions.

75. • Absence of RBC and presence of lymphocytes.
• Basement membrane shows discontinuity.
• Lymph vessels draining the pulp and PL have
common outlet.
• Anterior teeth: drained to submental lymph
nodes.
• Posterior teeth: drained to submandibular and
deep cervical lymph nodes.

76. Nerves
• Majority- Non Myelinated and many of these
gain myelin sheath later in life.
• Found in close association with blood vessels,
many being sympathetic in nature.
• They have terminals on the muscle cells of the
larger vessels and function in vasoconstriction.
• Thick nerve bundles enter the apical foramen-
pass along the radicular pulp to the coronal pulp
where the fibres separate and radiate
peripherally to the parietal layer of nerves.

77. • Number of fibres in the bundles varies greatly.
150->1200
• Larger fibres: 5-13µm in size.
• Majority are smaller than 4µm.
• The peripheral axons form a network of nerves
located adjacent to cell rich zone, called as
Parietal layer of nerves / Plexus of Rashkow.

79. • Axons of Raschkow plexus lose their myeline
sheath (but not their Schwann cells) as they
penetrate the cell-rich and cell-free zones to
make synaptic contact with the odontoblast cell
body in the pulp or odontoblastic process within
the dentinal tubule.
• Raschkow plexus is responsible for transmitting
pain sensation from the pulp of the tooth.

80. • By virtue of their peptide content they also play
important functions in inflammatory events and
subsequent tissue repair.
• There are two types of nerve fiber that mediate
the sensation of pain:
• A- fibers and C-fibers.
• A-fibers conduct rapid and sharp pain
sensations and belong to the myelinated group.
• C-fibers are involved in dull aching pain and are
thinner and unmyelinated.

81. • The A-fibers, mainly of the A-delta type, are
preferentially located in the periphery of the
pulp, where they are in close association with the
odontoblasts and extend fibers to many but not
all dentinal tubules.
• The C-fibers typically terminate in the pulp
tissue proper, either as free nerve endings or as
branches around blood vessels.

83. Nerve Endings
• Nerve axons pass between odontoblasts to
terminate adjacent to the odontoblast processes
at the pulp-predentin border or in the dentinal
tubules.
• Nerve terminals consist of round or oval
enlargements of terminal filaments that contain
microvesicles, small, dark, granular bodies and
mitochondria.
• Close to odontoblast plasma membrane,
seperated only by a 20µm cleft.

84. • Believed to be sensory receptors.
• Function whether relative to capillaries or
odontoblasts in dentinogenesis, is not known.
• More nerve endings found in pulp horns than in
other peripheral areas of coronal pulp.

85. Pulpal Stem Cells

86. - Stem cells are the body’s "master" cells that
regenerate the body’s many cells, tissues, and
organs.

87. • The most commonly known source of adult
stemcells is bone marrow, which contains both
hematopoietic stem cells (also found in cord
blood) and mesenchymal stem cells (also found
in teeth).

88. Types of dental stem cells:
At least five different types of postnatal
mesenchymal stem cells have been reported to
differentiate to odontoblast-like cells.
• 1.Dental pulp stem cells(DPSC)
• 2.Dental pulp of human exfolliated deciduous
teeth(SHED)
• 3.Stem cells of apical papilla(SCAP)
• 4.Dental follicle progenitor cells(DFPC)
• 5.Bone marrow-derived mesenchymal
stemcells(BMMCS)

90. • Stem cell are also present in pulp.
• They migrate to the site of injured odontoblasts
and produce dentin.
• Transforming growth factor (TGF beta1) and
bone morphogenic proteins (BMP-2) -
proliferation and differentiation, and endothelial
cell injury, in the migration of these stem cells in
response to an injury.
• They were shown to develop adipocytes and
neural cells.

91. • Derived from Pulp tissues of exfoliated
deciduous teeth, Primary incisors and
Permanent 3rd molars.
• Recent studies show that pulp stem cells
synthesise osteoblasts, synthesise 3D woven
bone tissue chips in vitro and that are capable to
synergically differentiate into osteoblasts and
endotheliocytes.

92. Indications
• Dental Tissue Repair
- Repair damaged tooth tissues such as dentin,
periodontal ligament, dental pulp.

93. • Periodontal Regeneration
• Regeneration of Pulp in immature tooth.

94. • Whole Tooth Regeneration

95. Pulpal Calcifications

96. Very common occurrence present in 50% of all
teeth.
Pulp calcification is considered:
 a pathological process related to various forms
of injury.
 Pulp calcification may be of microscopic size or
may be large enough to be detected
radiographically.

97. • Coronal pulp form →
(discrete, concentric
pulp stones
• Radicular pulp form →
diffuse.(single or attach)
• Variable sizes
• The mineral phase
consists of carbonated
hydroxyapatite
Pulp stones occupying much of the pulp
chamber
Diffuse calcification near the apical foramen

99. Age Changes
1. Continued formation of secondary dentin → ↓
size of pulp chambers & canals.
2. ↓ cellularity.
3. ↑ # and thickness of collagen fibers.
4. ↓ # of nerves & blood vessels.
5. ↑ Peritubular dentin, dentinal sclerosis & dead
tracts.