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Heart of the matter

• Every individual has a heart . And every lover knows…

• So, too does every tooth have a heart. And every dentist knows...

• Encased, this complex connective tissue presents a unique niche of specialization.

• We call it Endodontics!!

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The situation of this tiny heart• Development• Structure & Components • Function• Significance• Changes

Let us find out what makes this Pulp, tick ->

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• According to Cohen – By definition, the pulp is a soft connective tissue of mesenchymal origin residing within the pulp chamber and root canal of teeth.

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Neural tube

Condensed ecto-

mesenchymalcells

Dental papilla Dental Pulp

Development of the pulp

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Formation of Root Canal

• Apical proliferation of the Hertwig’sepithelial root sheath.

• Signals for odontoblast diff

• This acts as template for the root.

• Lateral Canals?

• Foramina Apex?

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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.

8Baume LJ (1980) The Biology of Pulp and Dentine. Monographs in Oral Science. Basel, Switzerland: Karger,159-82.

Histology

When the pulp is examined microscopically four distinct zones can be distinguished.

• 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.

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The Odontoblastic Zone

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20-45 µ

5-7µ

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Cell Free Zone

• Also called Zone of Weil

• 40µ thick. Under odontoblast layer.

• In pulps actively producing dentin, cell-free zone is absent.

• Arterioles, Sensory Nerves, Processes from dendritic cells

• Nerve plexus of Raschow (minor part)are present. neural sensation of the pulp.

• The ground substance metabolic exchange of the cells. & Limits spread of infection.

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Odontoblast layer Predentin Mineralization

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Cell Rich Zone

• The cell rich zone is located central to the cell free zone.

• Fibroblasts with their product of collagen fibres, undifferentiated mesenchymal cells and macrophages.

• Capillary network and major part of SPR.

• Found both coronally and in radicular pulp, it is much less obvious in the latter specially apically.

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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

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Organization of cells in the pulp

tight junction

nerve terminals

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Fun Fact: Each year, the 20th of September is an official holiday in China; this day is called “Love your teeth day”. Great people, aren’t they?

Pulp Cells

• Pulpal cells are in 4 groups

Progenitor cells – Fibroblast, Odontoblast

Defense cells – Lymphocytes, Macrophages

Amorphous interstitial substance –Proteoglycans and Glycoproteins

Fibrous interstitial substance – Collagen fibres

•Osborn JW, Ten Cate AR, Histologia Dental Avancada. 4th ed. Quintessence 1988. Pg 886•Stanley HR. The cells of the dental pulp. Oral Surg Oral Med Oral Path 1962 15:849-58

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Immunocompetent cells• Macrophages

-Antigen presenting cells -Pulp center -Unspecific immune response

• Lymphocytes & T-Cells -Along pulpal blood vessels-Specific immune response

• Dendritic cells -Forms a dendritic-cell-network -Infiltrates OB layer and Dentin

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Pulpal Defence Cells

Immune defence mechanisms of the dental pulp. Jontell M, Okiji T. Immune defence mechanisms of the dental pulp. Crit Rev Biol Med 1998; 9:179-200

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The first line of defense

“The Pulp is a small tissue with a big issue” – I.B Bender

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PULP CELLS – THE ODONTOBLAST

• The most promintent cells of the pulp dentin organ are the odontoblasts.

• Each odontoblast has an extension into a dentinal tubule

• Primary and Secondary odontoblasts- Primary, Secondary, Reactionary, and Reparative dentin• Barrier effect – interface between dentin formed by

primary odont, and that formed by odontoblast like cells

• They don’t communicate and act as barrier to prevent ingress of agents.

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Formation of the Odontoblast

Inner Enamel Epithellim

+ Mesenchyma

in dental papilla

During late bell stage,

TGF-β, BMP2, IGF and others

released

Most peripheral

cells of dental papilla get elongated

Pre-Odontoblast

Odontoblast

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Ectomesenchymal Cells PreodontoblastsOdontoblasts

Inner Enamel Epith Preameloblasts

Ameloblasts

Ameloblasts

Odontoblasts

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J D

esig

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Function of the Odontoblast

• 1) Secretion of the pre-Dentin matrix occurs adjacent to the cellular front.

• 2) Form dentin, but depend on it to form pulp.

• 3) Dental papilla (ectomesenchymal cells) exists till apexification is complete.

• 4) They can help in apexigenesis, i.e formation of radicular apex with dentin.

• 5) Study shows that OB form first line of defence against cariogenic bacteria

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Studies mentioned here regarding the Odontoblast

• Holland GR – the extent of the odontoblast in the pulp, J Anat 1976 ; 120:133-149

• Byers MR, Sugaya A. Odontoblast processes in dentine revealed by fluorescence. J Histochem Cytochem 1995; 43: 159-168

• Yoshiba K, Ejiri S, Yoshiba K, Iwaku M, Ozawa H. Distribution of odontoblast processes in human coronal dentin.

• Shimono M, Maeda T, Suda H, Takahshi K (eds). Dentin Pulp complex. Tokyo: Quintessence 1996: 287-288

• Köling A, Rask-Andersen H. Membrane junctions between odontoblasts and associated cells. A freeze fracture study of the human odontoblastic cell layer with reference to nerve supply. ActaOdontol Scand 1984; 42:13-22

• Ruch JV, Lesot H, Begue-Kirn C: Odontoblast differentiation.

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Pulp Cells - Fibroblast

• The cells of greater number in the pulp are the fibroblasts.

• Numerous in the coronal portion of the pulp, where they form the cell-rich zone.

• The function of the fibroblasts is to form and maintain the pulp matrix, which consists of collagen and ground substance.

• Apoptopic cell death of pulpal fibroblasts, especially in the cell-rich zone, indicates cell turn over.

• Desmosomes are often present in between them26

Components of dental pulp

Cells + (extracellular) Matrix

Fiber Ground substance

• Collagen

• Elastin

Structural Adhesive

• Fibronectin

• Laminin

• HA

• DS

• CS

GAG Proteoglycan

• Decorin

• Versican

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Extracellular matrix of the dental pulp - fibres

• Collagen is the main organic component of the dental pulp

• 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 zonesCa – 41%

• Type V and Type VI collagen form a mesh on the stroma of the pulpal conn. Tissue.

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

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Extracellular matrix of the dental pulp – ground substance

• Water- 88%

• Of the remining 12%: GAGs

Chondroitin sulphate -most abundant in the body (CS)-- 60%

Dermatan sulphate (DS) 34%

Hyaluronic acid 2%

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• 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. 30

Collagen in dental pulp

• Concentration varies from species to species, 32% in human pulp.

• Higher content in the middle and apical pulp.

• Total collagen decreases with age.

• Interestingly high level of collagen type III. (43%) : vascular content, tissue extensibility (cf. Elastin)

• Absence of elastin (except in b.v.).

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Fun Fact: According to Guinness World Records 2002, Sir Isaac Newton had the most valuable tooth of all times; his tooth was sold in London for $3,633.00 in 1816. Furthermore, this tooth was put in a ring.

Functions of the Pulp

• INDUCTIVE:

-Induce oral epithelial differentiation into dental lamina and enamel organ formation.

-Also induces developing enamel organ to become a particular type of tooth.

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FORMATIVE AND MORPHOLOGIC FUNCTIONS:

• -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.

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Lisi S, Peterkova R et al: Tooth Morphogenesis and pattern of odontoblast diff, Conn Tiss Res 44(sppl 1) 167, 2003.

• 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.

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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:

- The sensory nerves respond with pain to all stimuli. These initiate reflexes that control circulation in the pulp.

- This sympathetic function is a reflex, providing stimulation to visceral motor fibresterminating on the muscles of the blood vessels

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Haug SR, Heyeraas KJ: Modulation of the dental inflammation by the sympathetic nervous system, J Dent Res 85: 488-495, 2006

DEFENSIVE OR REPARATIVE:

• - It responds to insults whether mechanical, thermal, chemical or bacterial by producing reparative dentin and tubular sclerosis.

• Also acute stimulation may provoke inflammatory reactions and cardinal symptoms are set in motion including pain.

• 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.

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Kim S: Neurovasclar interactions in the dental pulp in inflammation, J Endod16: 48-53, 1990

PULPAL MICROCIRCULATION• There are cells, interstitial fluid, and a

capillary in the dental pulp

• Blood enters from the larger vessels as bulk flow

• Diffusion links blood plasma and interstitium

• The normal hydrostatic pressure in the interstitium of the pulp is about 5 to 20 mm Hg

• Being high, it plays a role in the sudden pain experienced when prep reaches unaffected dentin

• Lymphatic vessels transport fluid out of the pulp, and play a role in maintaining fluid balance 38

Pulp vasculature

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Pulp tissue is highly vascularized….

40-50 ml/min/100g

(Kim, 1985)

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Hydrau P: 35 at arteliolar end. 19 at venular

Dahl E, Mjor I. The fine structure of vessels in the human dental pulp. Acta OdontolScand 1971, 31:223 -230

Dental pulp interstitial fluid (ISF) and exchange of substances between plasma and ISF. (* values from Tonder and Kvinnsland, 1983; Ciucchi et al., 1995)

(5.5-10.3 mm Hg*)

(43 mm Hg)

(20 mm Hg)

(35 mm Hg)

Hydrostatic pressure in dental pulp

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Classes in Pulpal Vascularity

• Subodontoblastic capillaries (SC)

• Terminal arterioles (TA)

• Precapillary sphincters (PC)

• Postcapillary venules (PCV)

• Arteriovenous anastomosis (AVA)

• Lymphatic channels (LC)

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SEM micrograph- A-V shunt in pulp

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Takahashi K, Kishi Y, Kim S. SEM study of blood vessels of dog pulp J Endod 1982; 8:131-136,

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Fun Fact:In United States, the first woman to get a dental degree was Lucy Hobbs, from Ohio college of Dental surgery in 1866.

Basis of Innervation to the Tooth

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From C5 to the Brain!

Trigeminal (Gasserian) Ganglion

Syn

apse

wit

h 2

nd

ord

er N

.

Trigeminal Nuclear Complex –base of medulla

Cro

ss t

he

mid

line

Thalamic Nuclei

`

Sensory Cortex (higher centre)

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Classification of Nerve Fibres

• A Alpha – Motor, Proprioception

• A Beta – Pressure, touch

• A Gamma – Motor, to muscle spindles

• B - Preganglionic

• Sympathetic – Postganglionic sympathetic

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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

Types and properties of pulpal sensory nerve fibers

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

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Sensory Innervation

• V2 and V3 of the Trigeminal nerve (Sensory)

• Mand Premolars – sensory inn mylohyoid nerve of V3

• Mand Molars – sensory inn from C2 and C3

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NeuroAnatomy• Both myelinated and non-myelinated axons

• Most are Aδ axons Nociception

- Slow conducting, narrow, myelinated

• Less are Aβ axons. Proprioception & Mechanoreception

- Faster conducting, wider, myelinated

Both are seen in the dentin too!

• Few are C fibres non-myelinated

• Termination is always unmyelinated.

• Where? -

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Sympathetic Inn.

From T1, C8 and T2 via the superior cervical ganglion

Vasomotor tone in precapillary sphincters

Pressure and distribution of blood

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Innervations of the Dental Pulp

• Nerves enter by the apical foramen, along with afferent vessels forming the neurovascular bundle.

• The branches of these free, unmyelinated nerves end in an extensive plexus of nerves in coronal pulp – SPR

• In the root no plexus exists, only branches that arborize further in a specific territory.

• A small number of nerve endings bypass the plexus, and pass between the odontoblastic process, to enter the dentinal tubules.

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Pulpal Innervation

Plexus of Rashkow

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

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Nerve ending patterns

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Approx. 1800 non myelinated +400 myelinated

Intradentinal nerves are mostly found in pulpal horns

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Fun Fact:

In Germany, in the Middle Ages, kissing a donkey was the only treatment for painful teeth.

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PULPAL INFLAMMATION

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Cardinal Response (1st)

•Heat and redness by in blood flow•Swelling from interstitial tissue fluid coz of capillary perm.

PULPAL INFL. (Contd)

Rigid, non compliant chamber

Cannot swell, or expand

Tissue fluid

pressure

Strangle the apical

foramen

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Mjor IA, Tronstad L (1972) Experimentally induced pulpitis. Oral Surgery 34,102-8.

• Zone of Influence

• As Int fluid pressure local capillaries balance this

• Thus vessels remain patent

• During Injury, the gradients allow greater exchange

• Lymphatics become heavily employed

• Anastomoses allow blood shunting around injury

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Repair Necrosis

About I, Murray PE, FranquinJ-C, Remusat M, Smith AJ (2001) Pulpal inflammatory responses following deep restorations. Operative Dentistry 26,336-42

Pulpal Injury

• Pulpal injury can occur through deep seated dental caries, apical periodontitis, and even tooth preperation involving the tertiary dentin.

• The pulp responds to injury in a typical inflammatory response

• This response is termed as Pulpitis

• It can be acute or chronic, depending on the factors that triggered it.

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Pulp venules

STIMULATION

Increased pulp interstitial fluid

Increased pulp pressure

Increased tubular fluid flow

Release of inflammatory

agents?

Increased blood viscosity and rbc congestion in

capillary bed

Increased A-V shunt blood flow

Outward dentinal fluid flow and aspiration of

odontoblasts

CNS, Pain, Reflexes

Vasodilation, Increased permeability

Pulpal axonal reflex due to deep dentine stimulation

Without infection, Vascular changes couldbe resolved.

Axon reflex

SP, CGRP

Dentine

62©AJ Design

Murray PE, About I, Lumley PJ, Smith G, FranquinJ-C, Smith AJ (2000b) Postoperative pulpal and repair responses.Journal of the American Dental Association 131,321-9

Localized Response

Localized Effect

Extension of Effect

Progression of effect

Completion of Vicious

cycle

63Heyeraas KJ, Sveen OB, Mjor IA (2001) Part 3. Pulpal inflammation and its sequela. Quintessence International 32,611-25

Treatment options for painful conditions

Wait & seeTemporary Restoration

Replacement of

Restoration

Emergency exposure of

the pulp/ pulpotomy

Pulpectomy

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What to remember?

• Tissue pressure is a local phenomenon

• The pathophysiology of pulp is characterized not by a sudden strangulation at the apex

• Circumferential spread of inflammation and necrosis from a site of initial injury.

• Gross destruction -> loss of structural integ -> pulp becomes an isobaric chamber -> all areas are hydrostatic

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Iatrogenic Effects on the Pulp

• Local Anesthesic

• Cavity/Crown prep. -- heat

• Cavity depth.. RDC rep

• Cavity cleaning and cleansing

• Etching Dentin

• Polishing restorations

• Post-op Sensitivity

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Effect of Local Anesthesia

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•Blood flow to pulp is reduced to less than half of normal•When pulp is alread compromised, this is sometimes a stressor•If necessary pulp can produce energy through the Pentose-Phosphate pathway of carbohydrate metabolism

Engstorm C, Rockert HO: Effects of LA on aerobic and anaerobic metabolism of pulp: Swed Dent J 4(3): 119, 1980

Effect of Cavity Prep• Frictonal Heat: Esp in historical handpieces –

heavy torgue, low rpm and steel burs• Caused scorching of pulp• RDT of 1 mm protects pulp thermally as Dentin is

an effective insulator• ‘Boiling away’ of tubular fluid leads to dessication

by the heat produced. Intense sensitivity• ‘Blushing’ of dentin – hemorrhage due to

frictional heat. • Solution: Bur-dentin interface wetness & finishing

with hand instruments

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-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

• Dentin permeability increases with cavity depth

• Due to increase in both diameter and density of tubules

• Length of the tubule beneath the cavity is important

• That much further the substances have to diffuse

• That much more dilution & buffering by dentinal fluid 1mm – Shields Pulp

0.5- 0.25mm – Tertiary Reactive Dentin

.25mm> ~ Odontoblasts die & Reperative dentin is formed very fast.

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Cavity Drying

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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)

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-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

Pulpal Microbiology

• Routes of Pulpal Infection

o Dentinal Tubules

o Direct Exposure

o Periodontal Disease

o Anachoresis

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Infections

Intraradicular

Primary

Virgin

Anaerobic, facultative, Make use of disease

environment

Secondary By professional intervention usually

PersistentRecurrent infective.

Gm +ve facultative, anaerobes

Extra-radicularPeri-radicular

tissueApical

actinomycoses

Types of Endodontic Infections

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Microbiota of the diseased pulp• Gm –ve: Treponema

Fusobacterium

Prevotella

Capnocytophage

• Gm +ve: Actinomyces

Corneybacterium

Enterococcus

Streptococcus

In RC treated teeth:

E.faecalis in 30 to 90% cases

Resistance to intracanal medications

Ability to form biofilms

Endure long periods of nutrient starvation

74-Sundqvst G, Figdor D, Persson S, Sjogren U: Microbiological analysis of teeth with failed endo treatment and outcome of retreatment. Oral Surg Med Pathol 85:86, 1998-Love RM, Jenkinson HFL: invasion of dentinal tubules by oral baceria. Crit Rev Oral Biol Med 13: 171, 202

Pointers - Bacterial invasion of tubules

1. Outward movement of dentinal fluid & contents delay tubal invasion

2. Dentinal sclerosis beneath carious lesions, rep dentin, intratubular accumulation of host defence cells also impede

3. If pulp is necrotic, exposed tubules can become avenues for colonisation

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• Dental Pulp Calcification And Changes With Age

••

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STEM CELLS

• Hematapoietic Stem Cells (HSC)

• Mesenchymal Stem Cells (MSC)

• Embryonic Stem Cells

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Potential Uses For Dental Pulp Stem Cells

• Since these cells are multi-potent and can repair many different types of tissue

• Research shows that preserving these stem cells may allow your child future access to potential regenerative therapies, such as repair of the heart, brain, bone, cartilage

• Dental Pulp - Give your child the medical advantage . . .

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Definition of Terms• Pulp Cap: Treatment of an exposed vital pulp in

which the pulpal wound is sealed with a dental material, such as CaOH or MTA, to facilitate formation of rep.dentin & maintenance of vital pulp

• Direct Pulp Cap: Dental Materials placed directly on a mechanical or traumatic pulp exposure

• Pulpectomy (pulp extirpation): The complete surgical removal of the vital pulp

• Pulpotomy (pulp amputation): Surgical removal of the coronal portion of vital pulp as a means of preserving vitality of the remaining radicular portion and is performed as an emergency temporary measure for relief of symptom or therapeutic measure

80All definitions are from the Glossary of Terms, American Assn of Endodontics, Chicago Conf 2005

Definition of Terms (2)• Partial Pulpotomy (Shallow/Cvek Pulpotomy): The surgical

removal of a small diseased portion of vital pulp as a measure of preserving the remaining coronal and radicular pulp tissue

• Apexification: Inducing a calcified or artificial barrier in a root with an open apex or the continued development of an incompletely formed root in teeth with necrotic pulp.

• Apexogenesis: A vital pulp therapy procedure performed to enable continued physiologic development and formation of the root end; term used to describe initial pulp therapy that encourages the continuation of this process

81All definitions are from the Glossary of Terms, American Assn of Endodontics, Chicago Conf 2005

Fun Fact:

In the 1700’s people would sell their teeth to the rich people, who then used to make false teeth with them.

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Fun Fact:

In 1994 a prison inmate in West Virginia braided floss into a rope, scaled the wall and escaped 83

Fun Fact:

The electric execution chair was invented by a dentist. Makes you a wonder a whole lot about the dentist's chair, doesn't it?

84Dr. Richard Ruemenapp , Streetdirectory Malaysia.

Fun Facts:

50% consider the smile the first facial feature they notice.

80% are not happy with their smile.

83% of people believe their teeth are more important to their appearance than hair and eyes.

85Academy of General Dentistry, USA

Fun Fact:

Many people in Western Europe tell their children that if they keep an extracted tooth under their pillow before sleeping, a tooth fairy comes and exchanges the tooth with a gift.

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