3- dentino-pulp complex (mahmoud bakr)

7/27/2019 3- Dentino-pulp Complex (Mahmoud Bakr)

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Griffith UniversityOral Biology 2

1009 DOH

Dentino-pulp Complex

Dr. Mahmoud Bakr

Lecturer in General Dental Practice

B.D.S, M.D.S (Cairo University), ADC (Australia)Member of the Australian Dental Association (ADA),

the Australian Biology Institute Inc. (ABI) and the

Egyptian Dental Union (EDU)


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Learning objectives:After completing this lecture you should be able to:

1- Name, classify, identify and describe the

structure and function of the components of

Dentin.

2- Describe age related changes to Dentin and their

effects.

3- By observing the histological details of cells and

tissues, you should be able to use a microscope toidentify different histological structures of Dentin

and understand the histological processes

involved in preparing slides.


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All Microscopic images are taken from the

Digital Library of the Oral Biology

Department (Cairo University).


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Dentin: is the

mineralized tissue

that forms the main

bulk of the tooth

In crown it is

covered by enamel

In root it is covered

bycementum

(about 3-10mm thick

or more)


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Blade Shaft Grip

ENAMELCEMENTUMDENTINE

TOOTH DESIGN: Spear me

ENAMEL CEMENTUMDENTINE

Shaft is hollow forPULP

Hand represented by

PERIODONTAL LIGAMENT

& ALVEOLAR BONE

Refinements

Closer to true proportions


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Dentin consists of large

number of small parallel

tubules in mineralizedcollagen matrix.

Tubules contain longprocess (odontoblastic

process or Tomes

Fiber).Odontoblast is dentin

forming cell.


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Two major properties differentiate

dentin from enamel

Dentin issensitive

Dentin is formed

throughout life.


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Physical Characteristics

Light yellowish in color. Visco-Elastic.

Hard ( less than enamel but more

than cementum and bone). By X-ray : more radiolucent (darker)

than enamel and more radio-opaque

(lighter) than cementum. Dentin is semi-permeable to certain

ions.


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Collagentype I Proteoglycans &

phosphoproteins

glycoproteins

and lipids

Hydroxyappatite

crystals

70% inorganic

material

20% organic

material

Chemical Characters Of Dentin

10% water


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Inorganic materials They are in the form of calcium hydroxyappatite

crystals which consist of important elements.

calcium 26.9%.

Phosphorus 13.2%.

Carbonate 4.6%. Sodium 0.6%.

Magnesium 0.8%

Some trace elements as copper, iron, fluoride &zinc.

The crystals are plate like shape.

The crystal about o.o5-o.o6um in length may

reach up to 0.1um.


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Organic matrix

Collagen fibers embedded in an

amorphous ground substance.

Collagen type I& traces of type III & V.

Most of the collagen fibers run parallel to

the pulpal surface.


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Dentinogenesis

Dentin is formed by odontoblastic cells. Odontoblastic cells originate from

*ectomesenchymal cells of the dental

papilla, following an organizing influence ofthe inner dental epithelium.

*The odontoblasts produce an organicmatrix that becomes mineralized to form

dentin. Thus the dental papilla is the formative

organ of dentin, so dentin formation is

connective tissue in origin.


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Life Cycle Of OdontoblastsDifferentiation of odontoblasts.-1

Differentiate from

the peripheral

dental papilla

cells (UMC)

At first become

short columnar

cell with many

stubby processes

I D E

Basement

membrane

The cells grow in length

(40u) and closely

packed together

Ameloblasts


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In early bell stage

*The cells of the inner dental epithelium are short& columnarand supported by basement

membrane that separated the epithelium from the

dental papilla.

*The dental papilla is formed ofSpindle shaped

cell, uniform in size Separated by loose

intercellular substance.

*The cells of dental papilla are

separated from the inner dental

epithelium by the cell free zone

differentiation:Odontoblast-1


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*The inner dental epithelium cells changes from short

cuboidal to tall columnar and their nuclei migrate toward

the pole away from the dental papilla.

Under the inf luence of the IDE the peripheral cel ls o f

dental papi l la becomeshort columnar shape & arranged

in a single layer below the basement membrane. Cell free

zone separate dental papilla from the basement

membrane.*The acellular zone between

the dental papilla &IDE is

gradually decreased as

odontoblasts differentiate &increase in size .

*As differentiation progresses the

cell grow in length and reach about

40 UM in height & 7 UM in width


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Differentiation of odontoblasts

The

undifferentiated

ecto-

mesenchymal

cell

The UDMS of

the dental

papilla divideswith the

mitotic spindle

perpendicular

on the BM

Epithelial cells

Two daughter cells

Odontoblast

Subodontoblast cell


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predentinFormation of the-2Odontoblast become a protein forming and secreting

cell.

R E R , Mitochondria and Golgi bodies

Ribonucleic acid and alkaline phosphatase

Inner dental

epith side

Large open

faced N

R E R

Mitochondria

Golgi

bodiesPredentin


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At first more than one

process

As more D is laid down, the

cells receed and leave single

process ( Tomes fiber)

process formation:Odonotblastic-3


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The odontoblasts decrease in size and form

dentin in a slowly diminishing rate until

stimulated to form reparative dentin.

Quiescent state of odontoblasts-4


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To conclude:


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Life cycle of odontoblasts Pre-odontoblasts

Small, ovoid cells,high nucleus / cytoplasmic ratio,

Rudimentary rough endoplasmic reticulum, poorly developed Golgiapparatus.

Secretory odontoblasts (Cell body & odontoblastic process)

Large plump cell, open face nucleus situated basaly & basophiliccytoplasm.

Pronounced Golgi complex, RER, intercellular skeletal proteins actin,vinculin & vimentin, as well as cytokeratin.

junctional complexes and gap junctions.

Resting odontoblasts:

The cell inter quiescent state after dentin formation and mineralizationis completed & the dentin formed in very slow rate.

Reduction in length & cytoplasmic organelles and increase in numberand size of lysosomes& phagosomes.


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preodontoblast

Small

Ovoid

CellRudimentary

RER

Poorly developedGolgi apparatus

Odontoblastic process


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Secretory odontoblast

Odontoblastic process

predentin

Junctional complex

Secretory granules

Golgi apparatus

Centriole

Mitochondria

Nucleus

Nucleolus


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Transitional

odontoblast

Vacuole

Aged

odontoblast

Reduction

In length &

cytoplasmic

organelles.

Increase in

number & sizeof lysosomes

and

phagosomes


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Dentinogenesis

1 Matrix formation

(Predentin)

Collagen Ground

fibers substance

2 Maturation

(mineralization)

Hydroxyapatite

crystals


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Matrix formation-1

A- Mantle dentin The first formed dentin

layer in crown and root

Fibers are perpendicularto D E J

Fibers are parallel to

basement membrane


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B) Circumpulpal dentin

Mantle dentin

Circumpulpal

dentin. The fibersare parallel to DEJ

( right or oblique

angle to DT)

Crowding of thecells and

appearance of

junctional

complex


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Mantle dentin

Thickness: 10-20 um

Diameter of collagen

fibers: large (0.1-0.2 um) Direction of collagenfibers : have right angleto DEJ and parallel tobasement membrane inroot

Ground substance: fromodontoblasts and thecell free zone

Mineralization: linearform (contains matrixvesicles).

Circumpulpal dentin

Thickness: bulk of the tooth

Diameter of collagen fibers:

small (0.05um) Direction of collagen fibers :have right or oblique angle todentinal tubules (parallel todentin surface)

Ground substance: fromodontoblasts

Mineralization: Globularbelow mantle dentin thenbecome mixed in theremaining circumpulpaldentin (no M V ).

CrownRoot


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Mineralization-2Budding of

matrixvesicles

Rupture of matrix

vesicles

Mineralization of the

mantle dentin

Has

membranerich in

alkaline

phosphatase

Calcium and

phosphate

ions undergo

crystallization

Matrix

vesicle


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Pattern Of Mineralization

M V in

matrixCrystal

lization

Lodgment

of crystalsRupture

1- Linear at the

mantle dentin area

2- Globular incircumpulpal

dentin just below

mantle dentin

3- Combination inthe remaining

circumpulpal

dentin of the

crown and root


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How To Study The Histological

Structures Of Dentin

Ground section

(inorganic part)

Decalcified section

(Organic part)


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Types Of Dentin

Mantle

dentin

Circum-

pulpal

dentin

Primarydentin

Sec.Ir D

Sec.

RD

Dentin

Predentin

Odontoblasts

Secondary

dentin Predentin

Hi t l i l St t Of


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Histological Structure Of

Dentin

1- Dentinal tubules.

2- Inter-tubular dentin.

3- Peri-tubular dentin.

4-Interglobular dentin. 5- Tomes granular layer.

Incremental lines:

a - Incremental line of VonEbner.

b - Contour line of Owen.

c - Neonatal line.


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Histological Structure Of Dentin

Odontoblasts

Predentin

Dentin

Dentinal

tubules


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Odontoblasts And Dentinal Tubules

D E J

Odontoblastic

process

Preodontoblastic

spacePeritubular

dentin

Intertubular

dentin

Odontoblasts

Mant

leD

Circumpulp

alD

Predentin


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Dentinal tubules are

tapered structures

2.5 Um in diameter

near the pulp. No. of

D.T.76,000/mm

1.2 Um in diameter at

midpoint of dentin. No.

of D.T. 40,000/mm

900 Um near the DEJ.

No. of D.T. 30,000/mm

Ratio

between

number of

tubu les/ uni t

areaon the

pulpal andouter

surface is

4:1


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Lateral

branches orcanaliculi

Terminal

branches

Enamel

spindle


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Ground Section Of D. Ts.

At the cusp tip

or (incisal edge)

At cervical

area

Mid portion

of root and

apically

Straight

S shape

Straight

Secondary

curvatures


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Dentinal Tubules

Odontoblasts

PredentinDentin

Sec.

curvature

s

Terminal

branches


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T.S. In Dentinal Tubules

Ground section

Neumanns

sheath

Odontoblasticprocess (Tomes

fiber)

Periodontobl

astic space

Scanning microscope

Decalcified section


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Contents of dentinal tubules 1- The odontoblastic processes.

2- Afferent nerve terminals. 3- Dentinal fluid or dentinal lymph.

Structure of the odontoblastic process

A- microtubules& intermediate filaments runlongitudinally throughout the odontoblasticprocess.

B- mitochondria in odontoblastic process presentin predentin.

C- strands of RER & lysosomal elementoccasionally seen.

D- vesicles of variety of sizes are present denser

near the cell membrane.


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Intertubular dentin

Dentin located between the dentinal

tubules.

Represent the primary secretory product

of odontoblasts.

It consists of tightly interwoven network of

type I collagen fibers in which apatite

crystal are deposited.

It forms the main bulk of dentin.

Peri - tubular dentin (Intra tubular dentin)


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Peri - tubular dentin (Intra- tubular dentin) Highly calcified dentin.

It is about 40% more mineralized than inter-tubular

dentin. Width of the peri-tubular dentin at pulp end0.4U and 0.7 U at the DEJ.

It is deposited on the internal walls of the dentinaltubules narrowing the size of the lumen.

In ground section passing transversallythrough thedentinal tubules shows that the peri-tubular dentinseen as translucent rings.

It was p rev ious ly though t that, the sharpboundary of this ring was due to present specialstructure known as Neumann sheath.

E/M failed to prove the present of this sheath and

the organic fibers of peri-tubular dentin continuouswith the fiber of the inter tubular dentin.


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Interglobular Dentin

Calcification of dentin insome areas occurs in aform of globular pattern.

These globules fusestogether to form

homogenous substance. Sometimes globules in

some areas failed tofuse. Area of organicmatrix between the

globules remainuncalcified or partiallymineralized. These areasbonded by the curvedoutlines of the adjacentglobules.


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Tomes Granular Layer

Tomes granular

layer

Cementum


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Interglobular dentin (Size) Large (Cause)Areas of

unmineralized orhypomineralized dentin

(sometimes present). (Site)Appear in thecrown just below mantledentin.

(D T)Dentinal tubules

cross the IGD withoutthe peritubular dentin

(IL)Follow incrementalline pattern

In badly formed tooth it

appear in the root dentin

Tomes granular layer (Size)Small granular inappearance

(Cause)Areas of minuteIGD, but recent studies

indicate that it result fromthe looping of the terminalportions of DT which is aresult different orientationof odontoblastic process(always present) .

(Site)Appear in the rootadjacent to the cementum.

(DT)Dentinal tubules donot cross this layer

(IL)Does not follow anyincremental pattern.


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Incremental lines of dentin

1-Inc remental line of Von Ebner:

A 5 day rhythmic pattern of dentin deposition,

represented as increment lines separated by 20Um

intervals.

It can best be seen in longitudinal ground section. It runs at right angles to dentinal tubules

It marks the normal rhythmic pattern of dentin

deposition in an inward and root ward direction.

2-Con tou r l ine of Owen. Result from a coincidence

of secondary curvature between neighboring D.T.

3-Neonatal l ine.


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Incremental Lines Of Dentin

In

crementa

llines

ofvonEbn

er

Neonatal

line

Contour

line of

Owen


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Age Changes Of Dentin Regular secondary

dentin- Mild stimulus Occurs on the entire pulpal

surface. In multirootedteeth it is thicker on theroof and floor of pulp

chamber. The size of the pulp cavity

decrease and obliterationof the pulp horns (pulprecession)

The dentinal tubuleschange their direction to amore wavy course

The no of dentinal tubulesare fewer

Line of demarcation (dark).


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Primary den t in: dentin which formed

to produce the typical form of the root.

Secondary dent in: dentin developsafter root formation has been completed

and represent the continuing deposition

of dentin by odontoblast.

Irregular Secondary Dentin


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Irregular Secondary Dentin(Reparative or tertiary dentin)

Severe stimulus The dentin is formed at

a localized area.

The dentinal tubules areless in number andirregular inarrangement.

UMC from thesubodontoblastic layer

will differentiate andreplace the degeneratedodontoblasts to formreparative dentin

Irregular D T

T Of R i D i


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Types Of Reparative Dentin

Atubular dentin ( area

without dentinal

tubules)

Osteodentin (entrapped cells).

Vasodentin

(entrapped b.v.)

Secondary Dentin


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Secondary DentinRegular Cause:

Mild stimuli (slow attrition,slowly progressing caries&the early stages of cervicalcavities)

Site of formation:

Occurs on the entire pulpal

surface of the tooth ( thickeron the roof and floor of thepulp chamber in multirootedteeth).

Dentinal tubules:

- Change their direction and

have more wavy course- They decrease in number per

unit area.

Line of demarcation

Present and stained dark.

Irregular

Severe stimulus (abrasion,erosion, severe attrition anddeep caries)

Formed at the areacorresponding to the pulpal

end of the exposed dentin.

- Have irregular or twistedcourse

- They decrease in number andsome areas may have notubules

(a tubular dentin).

May or may not present

Clinically:


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Clinically:

The decrease of the

pulp chamber height

and obliteration ofthe pulp horns make

the liability of pulp

exposure during

cavity preparation

much less likely to

occur

The localized area of

dentin formation

increase the timetaken by caries to

reach the pulp

(barrier)

Transparent (Translucent OR


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Sclerotic )DentinMild stimulus leads to changes for the dentin

already present. It occurs in primary dentin.1- Odontoblast

and its process

undergo fatty

degeneration.

2- Then there will be

calcification of

dentinal tubules. First

become narrow by

widening of theperitubular dentin.

3- Then the DT

become obliterated.The affected area have occluded dentinal tubules, so

the dentin have uniform refractive index. So this area

of dentin appear translucent by transmitted light.



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Sclerotic )Dentin


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Transparent dent inoccurs as a normal aging

process as well as slow caries or abrasion. The

most likely source of calcium salts of dentinalsclerosis is the fluid ofdental lymphwithin the

tubules.

Transparent dent in:appeartranslucent whenseen with transmitted light. Appear dark by

reflected light.

Sclerotic dentin most common seen inthe apical third of the root and in the

crown midway between DEJ & the pulp.

Dead Tracts


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Dead Tracts Severe stimulation to

dentin leads to destruction

of the odontoblasticprocess and odontoblasts.

This leads to empty and

wide dentinal tubules.

These areas appear blackwith transmitted light.

Under the dead tracts from

the pulpal surface ,

reparative dentine will beformed.

The dead tract surrounded

by sclerotic dentin.


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Innervations Of Dentin

Plexus of Raschkow

(subodontoblastic layer)

The nerve will loose itsschwann coating then

pass between the

odontoblasts bodies and

enter the dentinal

tubules ( In crown and

fewer in the root )


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High at D E J

High near the

pulpal surface

Less sensitive

area

Theories Of Pain Transmission


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Theories Of Pain Transmission

Through Dentin.

Direct neural

stimulation

Odontoblastic

transduction

theory

Fluid or

hydrodynamic

theory

Di t l ti l ti


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Direct neural stimulation

Dent in contains nerve end ings wh ich

respond when dent in is st imu lated.

No evidence has been found for nerves in theouter dentin, which is the most sensitive.

The plexus of Raschkow and the intra-tubularnerves do not establish themselves untilsome time after the tooth erupted. Howeverthe newly erupted teeth are sensitive.

The application of local anesthetics to exposeddentin not eliminate dentin sensitivity. Andpharmacological agents cause pain whenapplied to skin do not cause pain when

applied to dentin.


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Odontoblastic transduction theory

The odontoblasts serve as receptors and

are coupled to nerves of the pulp. The

odontoblast is of neural crest origin, It

retains ability to transduce and propagatesan impulse.

But the synaptic relation between

odontoblast and pulpal nerves wasmissing.


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Fluid or hydrodynamic theory

The tubular nature of dentin permits fluidmovement to occur within the tubule whenstimulus is applied, a movement registered

by pulpal free nerve endings in the plexusof Raschkow close to the dentin.

The increased sensitivity at DEJ is explainby the profuse branching of tubules in thisregion.


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Clinical considerations

Permeabi l i ty o f dentin: the tubular structure of dentinallows the possibility ofsubstances applied to its outersurface able to reach and affect the dental pulp. Thisdepend on number of factors:

1- The dentin surface exposed by caries, attrition,

abrasion or trauma. 2-The tubules being patent. Tubules may occluded by

peritubular dentin or sealed off from the pulp by

reparative dentin.

3- Outward movement of dentinal fluid. 4- The substances are able to pass through the

odontoblast layer which presents a barrier to molecules

of higher molecular weight.

Th i ifi i l l


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The most significant materials to travel

down the tubules are:

1-The bacteria of dental caries and the

toxins they produce.

2- Components of dental materials oretchings used to prepare their placement.

Coronal dentin is more permeable over

the pulp horn. While the outer radicular

dentin has low permeability.

Adhesion of dental materials to dentin


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*Adhesion of restorative material to dentin is

more complex than to enamel because the

high organic content of the tissue and its

tubular structure.

Dentin is etched with strong acid to removethe smear layer and provide porous surface

that can infiltrated by the bond agent.

The bond agent then penetrate the dentinal

tubules and exposed collagen in the inter-

tubular dentin.


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The dental pulp is that loose

delicate connective tissue

occupying the cavity lying inthe center of dentin.

Morphology


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*The coronal pulp: it is present inthe pulp chamber.

*The radicular pulp: it is that part of

the pulp extending from thecervical region of the crown to the

root apex.

Morphology


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Accessory canals:

They are commonly seen to extendfrom radicular pulp laterally

through the root dentin to theperiodontal ligament.

in the apicalnumerousThey are

third of the root.

Accessorycanals

Mechanism of formation accessory


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1- it occurs in areas, where the developing rootencounters a large blood vessel, where dentinwill be formed around it.

2- Early degenerationof the epithelial rootsheath of Hertwig before the differentiation ofthe odontoblasts.

3-Lack of complete union of the epithel ialdiaphragmat the floor of the pulp chamber.

canals

*Apical foramen: The pulp organs are continuouswith the periapical tissue through the apical foramen


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lingual

with the periapical tissue through the apical foramen.

The average size of the apical foramen:maxillary teeth : 0.4 mm

mandibular teeth : 0.3mm

P l E


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Pulp Exposure


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Infected

pulp

Abcess


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Dental pain (acute pulpitis)


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Dental pain is the most un-killing acute pain

affecting human being.

Dental pain occurs in12% of the population.

The origin of the dentalpain is difficult to localize.

(referred pain)

Dental pain (acute pulpitis)

B 1910 root canal


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By 1910 root canal

therapy had reached itszenith and no self

respecting dentist wouldextract a tooth.

(T.R.Pitt Ford 2004)


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Loss of the pulpresults in loss of the

pulp functions, butthe tooth is still

functioning

Histological structure of the


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loosespecial izedThe dental pulp is formed ofconnective tissue:

gpulp

cells fibers intercellular substances

blood vessels and nerves

Zones of the pulp


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peripheral zone(odontogenic zone).

Central zone(pulp core).

Zones of the pulp

Dentin

odon togenic zone:


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a- odontoblasts:

Location: Adjacent to the predentin withthe cell bodies in the pulp and cell

processes in the dentinal tubules.

Dentin

:)Weil(the zone ofcell free zone-B


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:)Weil(the zone ofcell free zone-B

*It is present beneath the odontoblastic layer.

*It is suggested to be the area of mobilization andreplacement of odontoblasts.

C- cell rich zone:It is present beneaththe cell free zone.It is composed of

fibroblasts andundifferentiatedmesenchymal cells.


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odontogeniczone


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Cell free zone & cell

rich zone might beartifacts.

Cells of the pulp


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Cells of the pulp1- Synthetic cells (formative cells):

odontoblasts and fibroblasts.

Macrophages, lymphocytes, eosinophils,mast cells and plasma cells.

2- Defensive cells:

3- Progenitor cells:

Undifferentiated mesenchymal cells.

a- Odontoblasts


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Length: 25-40uDiameter: 5-7u

In the early stagesof development

odontoblasts consist of a single layer ofcolumnarcells .

In the later stagesof development, the

odontoblasts appeared piriformwherethe broadest part of the cell contains thenucleus


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Odontoblasts are

longerin the crown

cuboidalrootwise,

f latat the root apex

Th ll b f dj t d t bl t


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The cell membranes of adjacent odontoblasts

exhibit junctional complexes.

The clear terminal part of the cell body and the

adjacent intercellular junction is known as

terminal bars.

Gap junction

desmosome

b- Fibroblasts


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b Fibroblasts*These are the most numerous

type of pulp cells.

*They are spindlein shape.

*They have elongated processeswhichare link up with those of other pulpalfibroblasts (stellateappearance).

*The nucleusstains deep withbasic dye and the cytoplasmishighly stained and homogenous.


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These cells have a dual function: synthesizeand

d d ti f fib d d b t i th


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degradat ionof fibers and ground substances in the

same cell .

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

In periods of less activity and aging they


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In periods ofless activity and agingtheyappear smaller and round or spindle-shaped with

few organelles, they are termed fibrocytes.

fibrocyte fibroblast

Infected pulp


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Infected pulp

L

L

2- Defensive cells:


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A- Histiocyte (macrophage):

hey appear irregular in shape with short bluntprocesses.

he nucleus is small, more rounded & darkerin staining than fibroblast.

heir presence is disclosed by intra-vital

dyes such trypan blue.

hey are distributedaround the odontoblasts

and small blood vessels and capillaries.


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In case of inf lammation:

*Nuclei increase in size and exhibita prominent nucleolus.

*It exhibits granules and vacuoles

in their cytoplasm.

Ultastructural ly,

invaginations of plasma membrane

with aggregation of vesicles or

phagosomes .


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*Macrophages are involved

in the elimination of deadcells.

*Macrophages removebacteria and interact withother inflammatory cells to

protect the pulp duringinflammation.


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L

Phagocytosis


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Phagocytosis

Hydrolyticenzymes

b- Plasma cel ls:


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These cells are seen during

inflammation.

The nucleus of this cell is small and

appears eccentricin the

cytoplasm.

The arrangement of chromatin in

the nucleus gives the cell a cart

wheelappearance,

The plasma cells are known to

produce ant ibodies.

c- Lymphocy tes


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c- Lymphocy tes

They are found in normalpulp and they increaseduring inflammation.

Eosinophi ls


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Eosinophi ls

They are found in normalpulp and they increaseduring inflammation.

They have thecharacteristic bi-lobednuclei (like headphones).

d- Mast cel ls :


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d- Mast cel ls:

*They have a round nucleus and theircytoplasm contains many granules.

*They are demonstrated by usingspecific stains as toluidine blue.

*They produce histam ine& heparin.

3- Progenitor cells:


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3- Progenitor cells:(UMC):

They are smallerthan fibroblasts

but have a similar appearance.

They are usually found alongthewalls of blood vessels.

These cells have thepotentiality

of forming other types of

formative or defensive cells.

The ground substances of thepulp:


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pulp:

*The ground substances consists of acidmucopolysaccharides and neutral glycoprotein.

*These substances are the environment thatpromotes life of the cells.

*Glycoseaminoglycansare bulky molecules andhydrophilic, they form gels that fill most of the

extracellular space, They contribute to the high

tissue fluid pressure of the pulp

III-Blood vessels


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*The pulp is highly vascular. It is supplied

by the infer ior and superior alveolararteries.

*As the vessels enter the tooth, their

walls become considerably th inner

than those surrounding the tooth.

*Along their course they give numerousbranches in the radicular pulp that

pass peripheral lyto form a plexusin

the odontogenic region.

D

The normal hydraulic system of the tooth is importantbecause the dent in requ ires an act ive transpo rt ,


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q p

without which its rate of metabolism would not be

possible.

The pulp is designed to support this hydraulic system:

1-The rate of blood flow in the pulp of the tooth is four

t imethe rate of blood flow in resting muscle.

Laser Doppler FlowmeterIt measures the rate of

pulpal blood flow

2-The capillaries adjacent to the odontoblasts are


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fenestrated. Such capillaries are found in areas

of rapid exchange.


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Assessment of pulp vitality


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Current pu lp testsassess the function ofnerves in the pulp, by the application of electric

current or a rapid change in temperature.

Recently, blood f low ratein the pulp is used to

measure the degree of the pulp vitality.

Nerves of the pulp


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The pulp has an abundant nerve supply

which follows the distribution of the

blood vessels.

Two types of nerve fibers are

present:Nonmyel inatednerves:

*Sympathetic in nature.

*They control the contraction of thesmooth muscles of the blood vessels.

Myelinatedfibers which are sensory

parasympathetic nerves.


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*The peripheral non mylinated axons form anetwork of nerves located adjacent to the cell-rich

zone. This is termed the parietal layer of nerves

or plexus ofRaschkow.*More nerve endings are found in the pulp hornsthan in other peripheral areas of the coronal or

radicular pulp

Sensory response in the pulp cannot differentiatebetween heat, touch, pressure or chemicals.


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p

This is because the pulp organs lack those

types of receptors.

Heat,

Touch,

Pressure,

Chemicals

Pain

Functions of the pulp


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1- Induct ive:

Dental papilla induces the enamel organ

formation and also determines the

morphology of the tooth.

Functions of the pulp


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2- Formative :

Pulp organ produces dentin. Odontoblasts

develop the organic matrix and function in its

calcification.


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3- Nutri t ive :

The pulp nourishes the dentin. Nutrition ismediated through the odontoblasts and

their processes.

Dentin

4- Pro tective:


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4 Pro tective:

The sensory nerves in the tooth respond with

pain to all stimuli, Pain sensation is a useful

alarm system of the pulp.

5- Defensive or reparative:


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5 Defensive or reparative:

The pulp responds to irritation by producing

reparative dentin and mineralizingany affecteddentinal tubules.

These reparative reactions are an attempt to wall

off the pulp from the source of irritation.

The presence of macrophages, lymphocytes and

leucocytes aid in the process of repair of the

pulp.

Age changes in the pulp


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The size of the pulp

The apical foramen

The cellular elementsThe bl. vessels & n.

Vitality

Reticular atrophy :The total affect is the

production of a lessened vitality of the pulp

tissue and a lessened response to stimulation

decreased

Pulp clacification


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Pulp clacification

localized(pulp stones )

diffuse

False denticleTrue denticle

True denticles


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They consist ofi r regu lar dent in

containing traces of dentinaltubules and few odontoblasts.

Remnants of the epithel ial roo t

sheathinvade the pulp tissues

causing UMC of the pulp to form

thisirregular type of dentin.

odontoblast

dentinaltubules

True denticles are rare&

smallin size&found near the apical foramen.

False denticles


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*They are evidence ofdyst rophic

calcification of the pulp tissue .*They contain nodentinal tubules.

*They are formed of degenerated

cells or areas of hemorrhagewhich act as a central n idusforcalcification.

*Overdoses ofv it. D, may favor theformation of numerous denticles.

*Pulp stones are classifiedaccording to their location into:


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free, attached and embedded.

*They continue to increase in sizeand in certain cases they fill up the

pulp chamber completely.

*If pulp stones come close enoughto a nervebundle pain may be

elicited.

*The close proximity of pulp stonesto blood vesselsmay cause

atrophy of it.

free

attached

Diffuse pulp calcification


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p p

*Commonly occurs on top ofhyal inedegenerat ionin the

root canal and not common in

the pulp chamber.*They are i r regu lar calci f ied

deposi t ionsin the pulp tissue

following the course of bloodvessels or collagen bundles.

*Advancing agefavors their

development.


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3- dentino-pulp complex (mahmoud bakr)

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