The Hertwig epithelial root sheath (HERS) or epithelial root sheath is a proliferation of epithelial cells located at the cervical loop of theenamel organ in a developing tooth. Hertwig epithelial root sheath initiates the formation of dentin in the root of a tooth by causing the differentiationof odontoblasts from the dental papilla. The root sheath eventually disintegrates with the periodontal ligament, but residual pieces that do not completely disappear are seen as epithelial cell rests of Malassez (ERM). These rests can become cystic, presenting future periodontal infections.
The cell bodies are columnar with large oval media basally. Immediately adjacent are rough surfaced endoplasmic reticulum and Golgi apparatusThe odontoblastic process extends to varying lengths into the dentin. This is the formative zone of the pulp and its junction with dentinThis zone is adjacent to the predentin.LENGTH 20-45 mu breadth 5-7 mu
A Peripheral area of the pulp where theodontoblasts reside is termed odontogeniczone. The most promintent cells of the pulp dentin organ are the odontoblasts
The new dentin produced inresponse to the injury is called tertiary dentin.Some researchers define reactionary dentin asthe new dentin secreted by surviving primaryodontoblasts, in contrast to reparative dentin,which is produced by newly recruited secondaryodontoblasts
is used to describe cells that are Steps of a macrophage ingesting a pathogen:a. Ingestion through phagocytosis, a phagosome is formedb. The fusion of lysosomes with the phagosome creates a phagolysosome; the pathogen is broken down by enzymesc. Waste material is expelled or assimilated (the latter not pictured)Parts:1. Pathogens2. Phagosome3. Lysosomes4. Waste material5. Cytoplasm6. Cell membranefound in connective tissue, but are not fixed in place
Plasma cells, also called plasma B cells, plasmocytes, and effector B cells, are white blood cells that secrete large volumes of antibodies. They are transported by the blood plasma and the lymphatic system. Like all blood cells, plasma cells ultimately originate in the bone marrow; however, these cells leave the bone marrow as B cells, before terminal differentiation into plasma cells, normally in lymph nodesChromatin is the combination or complex of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are 1) to package DNA into a smaller volume to fit in the cell, 2) to strengthen the DNA to allow mitosis, 3) to prevent DNA damage, and 4) to control gene expression and DNA replication
Water- 88%Of the remining 12%: GAGs Chondroitin sulphate -most abundant in the body (CS)-- 60%Dermatansulphate (DS) 34% Hyaluronic acid 2%
BASEMENT MEMBRANEIt is a sheet like arrangement of extra cellular protein matrix at the epithelial-mesenchymal interface.
The branching point of terminal arterioles ischaracterized by smooth muscle clumps that actas sphincters which are under the local cellular &neuronal control
Terminal capillary network located in the“odontoblastic layer”2. “Capillary network” present
Several dental materials have shown to inhibit O2consumption Eg. ZOE , Ca(OH)2 & silver amalgamPulpal irritation causes increases incycloxygenase products, which is inhibited byZOEAs cellular composition reduces, the rate ofoxygen consumption decreases
Nerve fibers, mylinated & unmyelinated, enterthe tooth through the apical foramen
Fibrosis is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process. This can be a reactive, benign, or pathological state. In response to injury this is called scarring and if fibrosis arises from a single cell line this is called a fibromaFibrosis is similar to the process of scarring, in that both involve stimulated cells laying down connective tissue, including collagen andglycosaminoglycans. Immune cells called Macrophages, and damaged tissue between surfaces called interstitium release TGF beta. This can be because of numerous reasons, including inflammation of the nearby tissue, or a generalised inflammatory state, with increased circulating mediators. TGF beta stimulates the proliferation and activation of fibroblasts, which deposit connective tissue.
An denticles begin as small nodules but increasein size by incremental growth Classified as free, attached (or) embeddeddepending on their relation to the dentina) Free denticle – entirely surrounded bypulp tissueb) Attached denticle – Partly fused with thedentinc) Embedded denticles – Entirely surrounded bydentinIncidence as well as the size of pulp stones increasewith age.112
These stem cells give rise to all of the blood cell types. They are primarily used to regenerate the blood supply when it is compromised by disease. They are found in great supply within the blood system.These stem cells have the unique ability to differentiate into many types of tissue in the body including; bone, heart, cartilage, adipose and neuronal cells. They are an essential component for regenerative medicine. These are found in dental pulp as well as other systems in the body. These stem cells can be differentiated into any cell in the human body. They are not currently used in humans for treatment yet they are very valuable in the research arena. These cells are very primitive in that they have not begun to take on any specific cell function and are derived from an unborn fetus.
“THE PULP IS A SMALL TISSUE WITH A BIG
ISSUE” – I.B BENDER
Dr.Mohan Kumar Subramaniam, Post graduate,Dept of Conservative dentistry & Endodontics
STRUCTURE AND COMPONENTS
The pulp is a soft connective tissue of mesenchymal origin
residing within the pulp chamber and root canal of teeth
During the 8th week of IUL, there is condensation of the
mesenchmye under the enamel organ-Dental papilla.
The enamel organ enlarge and enclose the dental papilla
in their central portion.
Dental papilla controls the morphology & type of tooth
to be formed.
Dental papilla shows :
extensive proliferation of cells
Capillaries crowd around the odontoblast during active dentinogenesis
Rim of the enamel organ (IEE & OEE) is the cervicalloop.
Root formation is carried out by the proliferation of cells at the cervical loop.
It is the pulp occupying the pulp chamber of the crown of the tooth
In young teeth it resembles the shape of the outer dentin
It has six surfaces : occlusal, mesial, distal, buccal, lingual and floor.
Pulp horns are projections into the cusp
This pulp constricts at the cervical region where it continues as the radicular
It is the pulp occupying the pulp canals of the r oot of the tooth.
In the anterior teeth it is single and in the posterior teeth it is multiple
The radicular portions of the pulp is continuous with the periapical tissues
through apical foramen
As age advances the width of the radicular pulp is reduced, and so is the apical
Pulp cavity terminates at root apex as small opening called apical foramen
Radicular pulp continuous with connective tissue of the periodontium through
Diameter in an adult- maxillary teeth-0.4mm mandibular teeth-0.3mm
Wide open during development of root
Leads laterally from the radicular pulp into the periodontal tissue.
Presents in the apical third of the root sheath cells
Formed due to premature loss of HERS or when
developing root encounters a blood vessel.
Overall occurrence is 33%
May also be present at the furcation region
PULP DENTIN COMPLEX
the odontoblasts, cells
present at the pulp
surface which are
responsible for dentin
formation and the
dentin can be refered
to as the PulpoDentin
When the pulp is examined microscopically four distinct zones can be
The odontogenic zone composed of odontoblasts (at the periphery).
The cell free zone or Weil’s zone.
The cell rich zone.
The central region or zone containing large nerves and blood vessels.
CELL FREE ZONE
It is also called weil’s zone
40 microns wide & relatively free of cells, Traversed by
1. blood vessels
2. unmyelinated nerves
3. cytoplasmic process of fibroblasts
This zone is found below the odontoblastic zone
Represents the space into which odontoblasts move during tooth development.
CELL RICH ZONE
undifferentiated mesenchyml cells.
Also contains macrophages, dendritic cells and
Formed due to migration of cells from pulp proper
Mitosis seen when dead odontoblasts are replaced
Also contain young collagen fibres during early
The central connective tissue mass from the cell rich
It contains blood vessels and nerves embedded in the
pulp matrix together with fibroblasts.
In young pulps, the cell population is greater while in
older pulps fibre density is higher.
The neurovascular bundles enter / exit this core
through the apical foramen
Arranged in Palisading pattern.
Shape may vary,
cornal pulp- columnar
Midportion - cuboidal
These cells have large process extending into dentin
The no of odontoblasts corresponds to the number of dentinal tubules
Average no of odontoblasts estimated to 45,000 per Sq.mm of
The odontoblast process is a direct extension of
the cell body and occupies most of the space
within the dentinal tubules
Its diameter is 3 to 4 um at the pulp-predentin border
Mainly composed of protein-tubulin, actin and vimentin
Cavity or crown preparation may disturb odontoblast
processes, leading t0 irreversibly damage d
Functions of Odontoblast
Synthesis of organic matrix
Synthesis of non collagenous substances like
sialoprotein, phosphophoryn, osteocalcin ostenoectin & osteopontin
Intracellular accumulation of calcium
Degradation of organic matrix
Study shows that OB form first line of defence against cariogenic
• Secretion of the pre-Dentin matrix occurs adjacent to the cellular
They can help in apexigenesis, i.e formation of radicular apex with
Cells that occur in greatest number in the pulp
Function is to form, maintain the matrix that consists of collagens, fiber and ground
substance throughout the pulp
Numerous in the coronal portion of the pulp, where they form the cell-rich zone.
In Young teeth , Fibroblasts have abudant cytoplasm having numerous cell
Apoptopic cell death of pulpal fibroblasts, especially in the
cell-rich zone, indicates cell turn over
It has capability of ingesting and degrading the organic
These mesenchymal cells are distributed through
out the pulp, frequently around the perivascular
area - believed to be toti potent cell
They are Polyhedral shaped with peripheral
processes and large oval nuclei
Difficult to differentiate from fibroblast under light microscopy
Under adequate stimilus they may differentiate into odontoblast , fibroblast or
In older pulps, the number ofundifferentiated mesenchymal cells may
diminish,which may also reduce the regenerative potential of the pulp
The ability of connective tissue to generate and support local inflammatory
and immune reactions makes it an active participant in host defense.
These cells are recruited from blood stream and remain as transient inhabitants in
2. Mast cells
3. Plasma cells
basophils and monocytes.
MACROPHAGES IN PULP
Described as histiocytes (or) as resting wandering cells
Located close to blood vessel
Have several phenotypes
Macrophages are phagocytes, function of which are engulfment and digestion
of the foreign material
During inflammation they appear in large number to aid in defense of the
In all they constitute 8-9% of the pulpal cell population
Dark staining nucleus with cytoplasmic
Plasma cells are seen during inflammation of the
The plasma cells function in the production of
Plasma cells may be present in coronal pulp
They have small nuclei with radiating chromatin
that appears like a cast wheel
Peripheral arrangement of chromatin in
Occur in small groups in relation to blood vessels
Present only during pulpal inflammation
Have round nucleus and contain many dark staining
granules in the cytoplasm.
Their number increase during inflammation
The composition of lymphocytes in the pulp resembles that seen in other
These cells are scattered predominantly along the blood vessels in the pulp
proper, although numerically fewer among pulpal cellular elements.
Extra cellular structural protein,major constituent of connective tissue
Collagen fibers appear through out the pulp
Young fine fibers ranging in diameter from 10-12mm.
Pulp collagen fibers do not contribute to dentin matrixproduction
After root completion pulp matures and bundles of collagen fibers increase in
They scattered throughout the coronal or radicular
pulp,or they appear in bundles.These are termed diffuse or bundle collagen
Main types of collagen present are Type I and Type III
Type I – responsible for pulpal & core architecture, secreted by fibroblasts. Ca
Type III – backbone for vessels, nerves in the central pulp; mainly distributed
in cell rich, and acellular zones
Ca – 41%
Type V and Type VI collagen form a mesh on the stroma of the pulpal
Type IV and VI is a component of the basal membrane of the pulpal capillaries
It is a structureless mass,makes up the bulk of the pulp.
Consists of complexes of proteins,carbohydrate and water.
Broadly classified as
GAG found in pulp is mainly chondroitin sulphate, dermatan sulphate &
Proteoglycans occupy larger area and they provide protection against
During dentinogenesis,the ground substance show affinity for collagen and
They have capacity to bind with calcium and help in mineralisation.
FUNCTIONS OF PULPAL EXTRACELLULAR
• Maintain tissue’s physical properties and
• Control of growth and development and repairs
• Control of cell migration
• Control of diffusion of macromolecules
Nanci A. Dentin-Pulp Complex. In: Ten Cate's Oral Histology: Development, Structure, and Function. St.
Louis: Mosby, 2003.
Garant PR. Oral Cells and Tissues. Chicago:Quintessence, 2003.
The pulp organ is extensively vascularized.
They are supplied by the superior and the inferior alveolar arteries
The blood vessels gain entry into the pulp through the apical foramen and at
times through accessory foramen
The arterioles on entering the pulp shows a reduction in thickness of vessel wall
musculature and therefore luman size increases.
Pulpal blood flow is more rapid than in most other area of the body
The flow of blood in
Arterioles - 0.3 to 1mm/sec
Venules – 0.15mm/sec
Capilaries – 0.08mm/sec
Organization of Pulp Vasculature
Pulp is a micro circulatory system which lacks true arteries and veins.
The largest vessels are arterioles & venules which regulate the local interstitial
Function as exchange vessels regulating the transport of diffusion of substances
between blood and local interstitial tissue elements
They consists of single layer of endothelium surrounded by basement
Capillary pressure –35 mmHg
Capillary wall is 0.5μ thick & acts as semipermeable
Fenestrated capillaries & Continuous capillaries
(non fenestrated) are the types present in the dental pulp.
• They start as blind openings near Weil’s zone &
• The larger lymphatic vessels run along the blood
vessels & nerves
• Multiple collecting lymph vessels exit though the apical foramen & drain
lymph from pulp into the periodontium
• They transport lymph to the regional lymph node before it enters into
the blood vessels. This provides an immuno surveillance function.
Metabolism has been studied by measuring the rate of O2 consumption.
During dentinogenesis, rate of O2 consumption is high than after crown
Greatest metabolic activity is seen in the odontoblast layer.
Reduced pH of pulp causes decreases in O2 consumption as seen in pulp
In addition to the glycolytic pathway, the pulp has the ability to produce energy
through Pentose shunt pathway, suggesting that the pulp can function under
varying degrees of ischemia.
• Dental pulp contains sensory and motor fibers to
fulfill the vasomotor and defense function
• Sensory afferent fibers are branches of
maxillary & mandibular
division of trigeminal nerve.
• After entering the foramen, they arborize. Larger fibers are present in
the central zone. They divide as they proceed peripherally and coronally.
• Subjacent to the cell rich zone, the nerves branch extensively forming a
parietal layer of nerves- NERVE PLEXUS OF RASHKOW. This layer
contains both A and C fibers.
Above the cell free zone, myelinated fibers begin to lose their myelin sheath.
In the cell free zone, they form a rich network responsible for pain.
Nerve endings may also enter the dentinal tubules
incidence - 10-20% in cusp tips
1% at the level of CEJ
Motor nerves are supplied by the sympathetic division of autonomic nervous
They wrap around the arteries and terminate in the tunica media.
They control the diameter of the vascular lumen & therefore blood flow &
volume & ultimately the intrapulpal pressure.
Conduction velocity 30-70 m/s
Very low threshold, nonnoxious sensation
40% of myelinated fibers in
Functions not fully known
Conduction velocity -
Involved in fast, sharp pain
Stimulated by hydrodynamic
Sensitive to ischemia
Conduction velocity - m/s
Involved in slow, dull pain
Stimulated by direct pulp
Sensitive to anesthetics
Conduction velocity 0-2 m/s
Post-ganglionic fibers of superior
Vasoconstriction & Vasodilation.
Nerve ending patterns
Plexus of Rashkow
Induce oral epithelial differentiation into dental lamina and enamel organ
Also induces developing enamel organ to become a particular type of tooth.
Produces the dentin that surrounds and protects the pulp.
Odontoblasts develop the organic matrix and function in its calcification.
The cells also determine the form acquired by the coronal pulp chamber as
well as volume of the pulp.
Lisi S, Peterkova R et al: Tooth Morphogenesis and pattern of odontoblast
diff, Conn Tiss Res 44(sppl 1) 167, 2003.
- Dentin being avascular, depends on the underlying pulp for blood
- Nourishing the dentin through the odontoblasts and their
processes and the blood vascular system of the pulp.
Lijima T, Zhang J: Three dimensional wall structure and innervation of dental pulp. Microsc Res Tech 56:32,2002
Kramer IRH, The vascular architecture of the human pulp, Arch Oral Bio 2:177, 1960
Pulp helps in recognition of stimuli like heat ,cold, pressure & chemicals by
way of sensory nerve fibres.
Vasomotor innervation controls the muscular wall of blood vessels.This
regulates the blood volume and rate of blood flow and hence the intrapulpal
Haug SR, Heyeraas KJ: Modulation of the dental inflammation by the sympathetic nervous system, J Dent Res 85: 488495, 2006
Pulp has remarkable reparative abilities,
It responds to irritation by producing reparative dentin
Mild to moderate irritation results in continued
formation, sclerosis and intratubular calcifiction-(Tublar sclerosis).
Various cells of the pulp aid in the repair process. The rigid dentinal wall and
the unyielding, enclosure can lead to partial or complete vascular collapse and
necrosis of the pulp.
However, if the inflammation is not too severe, the pulp will heal via its
excellent regenerative properties.
Kim S: Neurovasclar interactions in the dental pulp in inflammation, J Endod 16: 48-53, 1990
Overall dimensions smaller.
Pulp chambers larger.
Roots are long and slender and root canals narrower and follow a
Pulp horns at a higher level, especially mesial horns of primary
Resorption starts soon after root completion.
Root resorption and dentin deposition changes size
shape and number of root canals.
REGRESSIVE CHANGES (AGING)
Appearance of fewer cells in aging pulp.
Cells are characterized by a decrease in size and no of cytoplasmic organelles.
endoplasmic reticulum , notable golgi complex & numerous mitochondria.
Fibroblast exhibit less perinuclear cytoplasm, long thin cytoplasmic processes.
Intra cellular organelles are reduced in number and size.
Diffuse fibrillar components
Accumulation of both
Bundles of collagen fibres
Fiber bundles may appear arranged longitudinally in the radicular pulp and more
diffused in coronal pulp.
Increase in fibers in the pulp organ is gradual and generalized.
External trauma such as dental caries (or) deep restorations cause a
localized fibrosis (or) scarring effect.
Increase in collagen fibers decrease s the size of the pulp.
Atherosclerotic plaques may appear in pulpal vessels.
Pulp stone or denticles are nodular, calcified masses appearing in either or both
in coronal and root portion of the pulp organ in teeth.
Asymptomatic unless they impinge on nerves (or) blood vessels.
Seen in functional as well as embedded unerupted teeth.
Goga, R.; N. P. Chandler & A. O. Oginni (2008). "Pulp stones: a review". International Endodontic Journal 41: 457–468.
True denticles are similar in structure of dentin.
They have dental tubules and contain processes of the odontoblasts
Usually located close to the apical foramen.
Development of true denticles is caused by the inclusion of remnants of the
epithelial root sheath with in the pulp
Epithelial remnants induce the cells of pulp to differentiate into
odontoblasts then form the dentinmass.
They do not exhibit dentinal tubules.
They appear as concentric layers of calcified tissue.
These calcification sites appear within a bundle of collagen fibers or they
appear in pulp free of collagen accumulations.
Center of these concentric layers of calcified tissues there may be remnants of
necrotic and calcified cells
Calcification of thrombi in blood vessels called phleholiths, may also serve as
nidi for false denticles
False calcification seen along the walls of the blood vessel
Appear as irregular calcific deposits in the pulp
collagenous fiber bundles and blood vessels.
Sometimes they develop into larger mass, persist as calcified spicules.
These calcifications are usually found in the root canal and less often in coronal
Ground substance alterations in the dental pulps
occurs on aging, such
changes may contribute to cellular degeneration and
may be the initiating factor.
Mineralizations also seen in the myelin sheaths of nerves.
Older, fibrotic pulp attract mineral salts more readily.
DM also increase as result of disease processes such as caries and periodontal
Teeth whose pulps one chronically inflammed
previous liquefaction necrosis.
contain DM in regions of
EFFECT OF PULP ON CAVITY PREPARATION
Frictonal Heat: In historical handpieces – heavy torque, low rpm and steel burs
Caused scorching of pulp
Remaning Dentin Thickness of 1 mm protects pulp thermally as Dentin is an
‘Boiling away’ of tubular fluid leads to dessication by the heat produced. Which
leads to Intense sensitivity
‘Blushing’ of dentin – hemorrhage due to frictional heat.
Solution: Bur-dentin interface wetness & finishing with hand instruments
-Murray PE, Lumley J, Smith AJ: Preserving the vital pulp in operative dentistry: 3. Thickness of remaining cavity
dentin as a key mediator of pulpal injury: Jent Update 29 (4): 172, 2002
-Mullaney TP, Laswell HR: Iatrogenic blushing of dentin. J Prosth Dent 22(3):354, 1989
1mm – Shields Pulp
0.5- 0.25mm – Tertiary Reactive Dentin
0.25mm> ~ Odontoblasts die & Reperative dentin is formed
Strong capillary forces
Outward flow of Dentinal
This is replaced by fluid from
Follow the same response pattern as mentioned above
Generally seen in –
Smear Layer Removal
Polishing Restorations ( 20° approx in amalgam)
Post Restorative Sensitivity (Microleakage of toxins & cytotoxic materials
-Camps J, Dejou J, Remesat M et al, Factors influencing pulpal response to cavity restorations. Dent Mater
16(6): 432, 2000
-Grajower R, Kaufman E, Rajstein J; Temp in the pulp chamber during polishing of restorations, J Dent Res
53(5): 1189, 1974