THE PULP“THE PULP IS A SMALL TISSUE WITH A

BIG ISSUE” – I .B BENDER

Dr.Mohan Kumar Subramaniam, Post graduate,Dept of Conservative dentistry & Endodontics

OVERVIEW

DEFINITION

DEVELOPMENT

STRUCTURE AND COMPONENTS

VASCULATURE

INNERVATION

METABOLISM

FUNCTIONS

AGE CHANGES

SIGNIFICANCE

The pulp is a soft connective tissue of mesenchymal origin residing within the pulp chamber and root canal of teeth

(Cohen).

The Development

• 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 :

a. extensive proliferation of cells

b. High vascularity

The Development

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.

CORONAL PULP

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 pulp

RADICULAR PULP

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 foramen.

APICAL FORAMEN

Pulp cavity terminates at root apex as small opening called apical

foramen

Radicular pulp continuous with connective tissue of the

periodontium through this foramen.

Diameter in an adult- maxillary teeth-0.4mm mandibular teeth-

0.3mm

Wide open during development of root

ACCESSORY CANAL

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 intimate

relationship

between the

odontoblasts, cells

present at the pulp

surface which are

responsible for

dentin formation

and the dentin can

be refered to as the

PulpoDentin

Complex.

HISTOLOGY

HISTOLOGY

When the pulp is examined microscopically four distinct zones

can be distinguished.

o The odontogenic zone composed of odontoblasts (at the

periphery).

o The cell free zone or Weil’s zone.

o The cell rich zone.

o The central region or zone containing large nerves and blood

vessels.

THE ODONTOBLASTIC ZONE

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

• subodontoblastic layer

• Contains more proportions of fibroblast and

undifferentiated mesenchyml cells.

• Also contains macrophages, dendritic cells

and lymphocytes.

• Formed due to migration of cells from pulp

proper

• Mitosis seen when dead odontoblasts are

replaced

• Also contain young collagen fibres during

early dentinogenis.

PULP CORE

• The central connective tissue mass from the

cell rich zone inward

• 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

CELLS OF PULP

ODONTOBLASTS

FIBROBLASTS

UNDIFFERENTIATED CELLS

DEFENSE CELLS

ODONTOBLASTS

Arranged in Palisading pattern.

Shape may vary, cornal pulp- columnar

Midportion - cuboidal

Apical region–Flattened

• 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 odontogenic zone.

Odontoblast process

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 odontoblasts(Odontoblast Aspiration)

%TERTIARY

REACTIONARYREPARATIVE

PULP

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 bacteria

• Secretion of the pre-Dentin matrix occurs adjacent to the

cellular front.

• They can help in apexigenesis, i.e formation of radicular

apex with dentin

FIBROBLAST

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 organcells

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

matrix.

UNDIFFERENTIATED MESENCHYME

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 macrophages.

In older pulps, the number ofundifferentiated mesenchymal cells may

diminish,which may also reduce the regenerative potential of the pulp

IMMUNOCOMPETENT CELLS

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 pulp

They are

1. Macrophages

2. Mast cells

3. Plasma cells

4. Lympocytes,Neutrophils,Eosinophils

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 organism

In all they constitute 8-9% of the pulpal cell population

Dark staining nucleus with cytoplasmicgranules

PLASMA CELLS

Plasma cells are seen during inflammation of the

pulp

The plasma cells function in the production of

antibodies.

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 innucleus

MAST CELLS

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

LYMPHOCYTES

The composition of lymphocytes in the pulp resembles that seen in

other connective tissues.

These cells are scattered predominantly along the blood vessels in

the pulp proper, although numerically fewer among pulpal cellular

elements.

MATRIX

FIBREGROUND SUBSTANCE

• COLLAGEN

• ELASTIN

• FIBRONECTIN

• LAMILIN

GAGPR

OTEOGLYCAN

COLLAGEN FIBRES

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 number

They scattered throughout the coronal or radicular

pulp,or they appear in bundles.These are termed diffuse or bundle

collagen

COLLAGEN FIBRES

Main types of collagen present are Type I and Type III

Type I – responsible for pulpal & core architecture, secreted by

fibroblasts. Ca – 56%

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 connective Tissue.

Type IV and VI is a component of the basal membrane of the pulpal

capillaries

GROUND SUBSTANCE

It is a structureless mass,makes up the bulk of the pulp.

Consists of complexes of proteins,carbohydrate and water.

Broadly classified as

Glycoaminoglycans

Proteoglycans

GROUND SUBSTANCE

GAG found in pulp is mainly chondroitin sulphate, dermatan

sulphate & hyaluronic acid

Proteoglycans occupy larger area and they provide protection

against compression.

During dentinogenesis,the ground substance show affinity for

collagen and influence fibrinogenesis.

They have capacity to bind with calcium and help in mineralisation.

• Maintain tissue’s physical properties and

integrity

• Control of growth and development and

repairs

• Control of cell migration

• Control of diffusion of macromolecules

FUNCTIONS OF PULPAL EXTRACELLULAR MATRIX

• 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.

34

PULPAL VASCULATURE

PULPAL VASCULATURE

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

APICAL THIRDMIDDLE THIRD

PULPAL VASCULATURE

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

PULPAL VASCULATURE

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 environment. ARTERIOLES(50μ DIAMETER)

TERMINAL ARTERIOLES

PRECAPILLARIES

METARTERIOLES

CAPILLARIES (8μ)

CAPILLARIES

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 membrance

Capillary pressure –35 mmHg

Capillary wall is 0.5μ thick & acts as semipermeable

membrane

Fenestrated capillaries & Continuous capillaries

(non fenestrated) are the types present in the dental pulp.

LYMPHATICS

• They start as blind openings near Weil’s zone &

odontoblastic layer

• 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

Metabolism has been studied by measuring the rate of O2

consumption.

During dentinogenesis, rate of O2 consumption is high than after

crown completion.

Greatest metabolic activity is seen in the odontoblast layer.

Reduced pH of pulp causes decreases in O2 consumption as seen in

pulp abscess.

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.

INNERVATION

• 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.

INNERVATION

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 system.

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.

A-delta fibers Conduction velocity 2-30 m/s Lower threshold Involved in fast, sharp pain Stimulated by hydrodynamic

stimuli Sensitive to ischemia Sharp pain

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

A-beta fibers Conduction velocity 30-70

m/s Very low threshold, non-

noxious sensation 40% 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 &

Vasodilation.

INNERVATION

P e n e t r a t i o n i n t o D e n t i n

Plexus of Rashkow

Nerve ending patterns

46

FUNCTIONS OF DENTAL PULP

INDUCTIVE

FORMATIVE

NUTRITIVE

PROTECTIVE

DEFENSE

INDUCTIVE

Induce oral epithelial differentiation into dental lamina and enamel

organ formation.

Also induces developing enamel organ to become a particular type

of tooth.

FORMATIVE

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.

NUTRITIVE

NUTRITIVE - Dentin being avascular, depends on the underlying pulp

for blood & drainage.

- 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 56:32,2002Kramer IRH, The vascular architecture of the human pulp, Arch Oral Bio 2:177, 1960

PROTECTIVE

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 pressure.

Haug SR, Heyeraas KJ: Modulation of the dental inflammation by the sympathetic nervous system, J Dent

Res 85: 488-495, 2006

DEFENSE

Pulp has remarkable reparative abilities,

It responds to irritation by producing reparative dentin

Mild to moderate irritation results in continued peritubular

dentin 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

DECIDIOUS PULP

Overall dimensions smaller.

Pulp chambers larger.

Roots are long and slender and root canals narrower and

follow a tortuous course.

Pulp horns at a higher level, especially mesial horns of

primary molars.

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.

Active pulpal fibrocyte (or) fibroblast has abundant rough-surfaced

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.

FIBROSIS 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 STONES

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.

CLASSIFICATION

True denticles

False denticles

Diffused calcificati

ons

TRUE DENTICLES

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.

FALSE DENTICLES

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

DIFFUSE CALCIFICATIONS

Appear as irregular calcific deposits in the pulp tissue, following

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 area.

DYSTROPHIC MINERALIZATION

Ground substance alterations in the dental pulps occurs on aging,

such changes may contribute to cellular degeneration and

increase dystrophic mineralization.

Circulatory disturbances 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 diseases

Teeth whose pulps one chronically inflammed contain DM in regions

of previous liquefaction necrosis.

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 effective insulator

‘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

CAVITY DEPTH

1mm – Shields Pulp

0.5- 0.25mm – Tertiary Reactive Dentin

0.25mm> ~ Odontoblasts die & Reperative dentin is

formed very fast.

CAVITY DRYING

Strong capillary forces

Outward flow of Dentinal fluid/Odontoblast displacement

This is replaced by fluid from the pulp

Stimulates Nociceptors

Produces Pain

Other effects

Follow the same response pattern as mentioned above

Generally seen in –

Etching Dentin

Smear Layer Removal

Polishing Restorations ( 20° approx in amalgam)

Post Restorative Sensitivity (Microleakage of toxins & cytotoxic

materials from restoration)

-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

STEM CELLS OF PULP

Hematapoietic Stem Cells (HSC)

Mesenchymal Stem Cells (MSC)

Embryonic Stem Cells