dentinogenesis(authorv.mazuru)

8/18/2019 dentinogenesis(AuthorV.Mazuru)

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SUMPh “ Nicolae Testemitanu”

Histology, Cytology and Embryology department

Dentine, Dentinogenesis,

Dental Pulp.

Assistant professor Vitalie Mazuru


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Dentine – hard tissue that forms the bulk of the tooth

Physical properties

Harder than cementum and

bones, but softer than enamel

High permeability Compressive and tensile

resistance

Pale yellow color

Contributes to the color of thetooth through translucent

enamel


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Chemical properties

70% inorganic/30% organic

SBST

Ca hydroxyapatite crystals(smaler than in enamel)

Collagen fibrills (I ↑↑↑, III, V)

Proteins (Phosphoproetins, Gla-proteins,

proteoGAG, acidic proteins, Growth Factors) Lipids


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Dentine tubule

Basic unit of dentine

Run from pulp chamber to DEJ/DCJ

Sectioned longitudinally have sigmoidappearance

Sectioned transversally – circular shape

In cusp zone and root are DT are straight,

on the lateral surfaces of the crown curved

Near to DEJ their density is low andincreases closer to the pulp (because of

inward moving of odontoblasts during

Dentinogenesis)

Are highly branched


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Dentinal tubule

Primary curvature

First convexity of DT proximal to

Odontoblast body, looking rootward

Secondary curvature

Second convexity of DT distal to

Odontoblast body, looking cuspward


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Dentinal tubule components

DT = Wall + cavity

Wall – peritubular (intratubular

dentine

Cavity – a cavity filled up with

organic components


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Dentinal tubule componentsPeritubular dentine is first

produced and deposited by

odontoblasts, is the most

mineralized (arrowed)

Dentine between peritubular

dentine is intertubular dentine.

Is about 15% less mineralized

than the first one (star).

Between PTD and ITD is located

Newman sheath (appears as a white

ring). Has the lowest degree of

mineralization.


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Dentinal tubule content

Tomes processes (apical elongations of

dentinoblasts responsible for dentine

formation)

Loose connective tissue

Fibroblasts

Nerve fibers (both M and UM)

Sensory terminals (predominant

location in the cusp area)

Dentinal fluid


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Branches of dentinal tubules

Small canaliculi by

which dentinal

tubules communicate

with each other

There are 3 types:1. Terminal (major)

2. Lateral

2a. Fine branches - sharp

angle (45º)

2b. Microtubules – right

angle (90º)


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Fine branches - sharp angle (45º)

Microtubules – right angle (90º)


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DEJ.

Terminal branches (major) of dentinal tubules. Are often entrapped into the

Enamel and form enamel spindles


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Terminal branches getting into DEJ


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Enamel spindles from DEJ


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Cross section through dentinal tubules. Silver impregnation

Dentinoblasts processesFine branches


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Types of dentine based on location

1. Peritubular D

2. Intertubular D

3. Mantle D

4. Circumpulpar D

Mantle D The oldest D

Thin layer of D in DEJ

Coincide with terminal

branches of dentinaltubules

Collagen fibers arearranged perpendicularly

to DEJ Less mineralized than

circumpulpar D

Absent in root area


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Mantle dentine


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Circumpulpar dentine

The bulk of dentine

Uniform in structure except

peripheral areas


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Types of dentine based on degree of

mineralisation

1. Predentine

2. Globular D

3. Interglobular D

4. Granular layer of Tomes

Predentine

The youngest one that

has been just produced.

Consists only of organic

matrix.

Is the closest to the

dentinoblasts bodies


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Predentine


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Globular DResult of normal mineralization of

organic matrix that occurs in

different points of Ca HA crystals

deposition. As a result appear manyglobular structures (calcospherites) –

responsible for globular appearance

of this Dentine. Is the most

Mineralized.

In root mineralization is largely

globular.

Interglobular D

D located between calcospherites.

Is less calcified than GD.

In time, due to the permanent

growing of calcospherites, globules

tend to fuse and replace IGD


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GD and IGD


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Interglobular D in DEJ


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Granular layer of Tomes

Located in DCJ

Spaces with air, similar

to dead tracts

Hypocalcified D


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Types of dentine according model of

development

A. Primary

B. Secondary

C. Tertiary

(reparative, reactive)

Primary D

D produced during

histodifferentiaton stage till

the tooth acquires the size

specific for an adult one


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development

Secondary D

Very similar to the primaryDentine, produced after

the tooth acquires the size

specific for an adult one.

Could be distinquished due

to the different angle of

dentinal tubules arrangement


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development

Tertiary

Appear when dental pulp is induced

by a variety of external stimuly: caries,

attrition, cavity preparation, trauma.

Is less calcified than previous two

Dentinal tubules have disorganizedarrangement


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Types of reparative dentine

Atubular D (areas without DT) Vasodentin (entrapped BV)


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Sclerotic Dentine

Appear normally in time

(elderly dentine) or as a

response for pathological

conditions

partial or complete

obliteration as a result of

peritubular D deposition in

excess

Highly mineralized

Appear as white areas


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Dead tracts

Appear under chronic and

strong stimulus action

Odontoblasts die

Empty tubules are filled

with air

Areas of weak resistance

Usually surrounded by

Sclerotic D

On ground sections, in

polarized light, appear black


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Dentine’s incremental lines

Appear as a result of incremental

pattern of D producing

1.cross-striation (daily deposition)

2. Von Ebner’s lines (6 to 10 days period)

3. Owen lines (periods of Odontoblasts

inactivity => hypocalcified areas)

4. Neonatal line (could be easily seen

between primary and secondary D)

Cross striation


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Owen linesRetzius lines


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Dentinogenesis

Formation of D

Odontoblasts

After induction from IEE

Outer pulp cells becomeelongated with many apical

processes, finally remains

only

one (Tome’s process).


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Dentinoblast life cylce

• Secretory stage

• Quiescent stage


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Dental pulp

Houses soft tissues of the tooth.

Cells and ECM

Ground substance

Collagen fibers (I, III)

Special cells (Odontoblasts, Hohl)Cells of LCT

Divided into 2 areas:

odontogenic

the core


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Odontogenic area

a) Layer of odontoblasts

b) Cell-free zone (Weil)

c) Cell-rich zone (Hohl)


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Odontogenic zone

dentinogenesis(authorv.mazuru)

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