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Dentin. Dentin – Composition , Formation , and Structures. Dentinogenesis. O rigin of the dentin.

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Dentin composition formation and structures
Dentin – Composition, Formation, andStructures



O rigin of the dentin
Origin of the dentin

Dentin is formed by cells called odontoblasts that defferentiated from ectomesenchymal cells of the dental papilla following an organizing influence that emanents from the inner dental epithelium.

Thus the dental papilla is the formative organ of dentin and eventually becomes the pulp of the tooth.


For dentinogenesis and amelogenesis to take place normally, the differentiating odontoblasts and ameloblasts will receive

signals form each other – “reciprocal induction”.


Stages of apposition
Stages of Apposition

  • 1. Elongation of inner dental epithelium;

  • 2. Differentiation of odontoblasts;

  • 3. Formation of dentin;

  • 4. Formation of enamel.


Preparation for the formation of tooth structures
Preparation for the formation of tooth structures

  • Continued growth of the tooth germ leads to bell stage, where the enamel organ resembles a bell with deepening of the epithelium over the dental papilla;

  • Continuation of histodifferentiation (ameloblasts and odontoblasts are defined)

    and beginning of morphodifferentiation(tooth crown assumes its final shape).


Start of dentinogenesis
Start of dentinogenesis

  • Begins after the final differentiation of the odontoblats and subodontoblasts;

  • Odontoblasts extended theire processes;

  • Released space under the basement membrane;

  • The first free space is in the growth center.


Enamel organ and dental papilla
Enamel organ and dental papilla

  • The cells of inner dental epithelium exert an organizing influence on the underlying mesenchymalcells in the dental papilla, which later differentiate into odontoblasts;

  • Outer dental epithelium - cuboidalcells that have a function to organize a network of capillaries that will bring nutrition to the ameloblasts.


Dental papilla and p reodontoblasts
Dental Papilla and preodontoblasts

  • Before the inner dental epithelium begins to produce enamel, the peripheral cells of the mesenchymal dental papilla differentiate into odontoblasts under the organizing influence of the epithelium;

  • First, they assume a cuboidal shape;

  • The basement membrane that separates the enamel organ and the dental papilla just prior to dentin formation is called the “membranapreformativa”.

preodontoblasts

Membrana

preformativa


Odontoblasts differentiation
Odontoblastsdifferentiation

Preodontoblast;

Undifferentiated cell;

Basement membrane;

4 and 5 - subodontoblastic cells.

It is brought about by the expression of signaling molecules and growth factors in the cells of the inner epithelium;

a.The dental papilla cells are small and undifferentiated and exhibit a central nucleus and few organelles;

At this time they are separated from inner epithelium by an acellular zone that contains some fine collagen fibrils;

b. Committed dental ectomessenchymal cells that are in a state of mitosis or cell division;

c.Daughter cells that are competent to become odontoblasts remain in the peripheral zone;

d.Differentiatedodontoblasts with a polarized nucleus and citoplasmicextentions;


Preodontoblasts
Preodontoblasts

  • A -preodontoblasts;

  • В – preameloblasts;

  • С –basement membrane;

  • With the begining of the production of dentin it becomes in dentinoenamel junction;

  • Differentiation of odontoblasts is mediated by expression of signaling molecules and growth factors in the inner dental epithelial cells.


A cellular zone
Acellular zone

  • This zone gradually is eliminated as the odontoblasts differentiate and increase in size and occupy this zone;

  • They are characterized by being highly polarized, with their nuclei positioned away from the inner dental epithelium

Acellular

zone


D ifferentiation of ectomesenchymal cells of dental papilla to preodontoblasts
Differentiation of ectomesenchymalcells of dentalpapillatopreodontoblasts

Almost immediately after cells of the inner dental epithelium reverse polarity, changes also occur in the adjacent dental papilla;

Ectomesenchymal cells rapidly enlarge and elongate to become preodontoblasts first and then odontoblasts as their cytoplasm increases in volume to contain increasing amount of protein-synthesizing organelles.


Short columnar cells bordering the dental papilla – inner dental epithelium will eventually become ameloblasts ;

5. The odontoblasts as they differentiate will start elaborating organic matrix of dentin, which will mineralize.

6. As the organic matrix of dentin is deposited, the odontoblasts move towards the center of the dental papilla, leaving behind cytoplasmic extensions which will soon be surrounded by dentin;

7. Therefore, a tubular structure of dentin is formed.


Differentiation of odontoblasts
Differentiation of dental epithelium will eventually become odontoblasts

The odontoblasts appear like protein-producing cells;


Odontoblasts and subodontoblasts
Odontoblasts and subodontoblasts dental epithelium will eventually become

odontoblasts

Dentin formation proceeds toward the inside of the tooth;

Sub

odontoblasts


Odontoblasts
Odontoblasts dental epithelium will eventually become

  • А – nucleus;

  • В -secretory end;

  • С - secreted matrix.

  • They are the dentin-forming cells, differentiate from cells of the dental papilla;

  • They begin secreting an organic matrix around the area directly adjacent to the inner enamel epithelium, closest to the area of the future cusp of a tooth;


Odontoblast process or tomes fiber
Odontoblast process dental epithelium will eventually become or Tomes`fiber

  • The odontoblast develops a cell process, the odontoblast process, which is left behind in the forming dentin matrix;

  • The organic matrix contains collagen fibers with large diameters (0.1–0.2 μm in diameter);

  • The odontoblasts begin to move toward the center of the tooth, forming an extension called the odontoblast process;


Odontoblasts large pear shaped cells
Odontoblasts dental epithelium will eventually become - large pear-shaped cells

  • Thus, dentin formation proceeds toward the inside of the tooth;

  • The odontoblast process causes the secretion of hydroxyapatite crystals and mineralization of the matrix.


Dentinal tubules formation
Dentinal tubules formation dental epithelium will eventually become

  • As the odontoblastic process elongates, a dentinal tubule is maintained in the dentin, and the matrix is formed around this tubule;


The b eginning of dentinal deposition
The b dental epithelium will eventually become eginning of dentinal deposition


Odontoblasts processes
Odontoblasts processes dental epithelium will eventually become

  • The plasma membrane of odontoblasts adjacent to inner epithelium extend stubby processes into the forming extracellular matrix;

  • On occasion one of these processes may penetrate the basal lamina and interpose itself between the cells of inner epithelium to form what later becomes an enamel spindles;


M atrix vesicles
M dental epithelium will eventually become atrix vesicles

  • As the odontoblasts form these processes, it also buds off a number of small, mambrane-bound vesicles known as matrix vesicles, which come to lie superficially near the basement membrane.



Odontoblast branching growths on the periphery of the dentin
Odontoblast a layer usually about 150  branching growths on the periphery of the dentin


Stages of deninogenesis
Stages of a layer usually about 150 deninogenesis

  • Formation of organic matrix:

    • Fibrogenesis;

    • Maturation of the organic matrix;

  • Mineralization of the matrix.


2 steps of dentinogenesis
2 steps of a layer usually about 150 dentinogenesis

  • Odontoblasts with cytoplasmic processes forming dentinal tubules;

  • 1. Formation of collagen matrix;

  • 2. Deposition of calcium and phosphate

  • (hydroxyapatite) crystals in the matrix.


Fibrogenesis
Fibrogenesis a layer usually about 150 ;


Synthesis of collagen and its arangement in fibrils and fibers
Synthesis of collagen and its a layer usually about 150 arangement in fibrils and fibers

  • The collagens in dentin are primery type I with trace amounts of type V collagen and some type I collagen trimer;

  • The type I collagen is a key structural component of dentin matrix.


Some of the fifteen known types of collagen a layer usually about 150 

Some types (of 15) of known collagen


Korf f s fibers formation
Korf a layer usually about 150 f`s fibers formation


Korff's a layer usually about 150 fibers (corkscrew fibers) passing between odontoblasts and reach predentin.

The question of the origin of these fibers is controversial.


Korff s fibers
Korff's a layer usually about 150  fibers

  • The first sign of dentin formation is the appearance of distinct, large-diameter collagen fibrils;

  • They are 0,1 to 0,2 µm in diameter and called von Korff's fibers;

  • They originate deep among the odontoblasts, extend toward the inner epithelium, and fan out in the structurless ground substance immediately bellow the epithelium.


Formation of the first loyer of dentin mantle dentin
Formation a layer usually about 150  of thefirstloyer of dentin – mantledentin

The next step in the production of dentin is formation of its organic matrix;

Odontoblasts differentiate in the preexisting ground substance of the dental papilla;

The first dentin collagen syntesized by them is deposited inthis groun substance.

Layer of polarized odontoblasts with Tomes' fibers.


Von Korff`s fibers appear as convoluted, threadlike structures that originated deep between odontoblasts

  • Following differentiation of odontoblasts, first layer of dentin is produced, characterized by appearance of large-diameter type III collagen fibrils (0.1 to 0.2 μm in dia) called von Korff’s fibers, followed by type I collagen fibers.


Odontoblasts and corkscrew fibers ( structures that originateKorff's fibers)

Odontoblastsandnerveendsbetweenthem.


Noncollagenous proteins
Noncollagenous structures that originate proteins

  • The other group of proteins is the noncollagenous proteins;

  • They are grouped into five categories;

    • The first and likely the most important group – two proteins, originally classified as dentin-specific:

      • DPP – dentin phosphoprotein;

      • DSP – dentin sialoprotein;

  • After type I collagen, DPP is most abundant of dentin matrix proteins and represent almost 50% of the dentin ECM.


DPP structures that originate

  • DPP has a high affinity for type I collagen as well as calcium and protein for initiation of dentin mineralization and is therefore considered a key protein for the initiation of mineralization;

  • DPP may also affect the shape and size of apatite crystals.


DSP structures that originate

  • DSP accounts for 5% to 8% of the dentin matrix;

  • DSP played a role in cell attachment;


A second category of noncollagenous proteins
A second category of structures that originatenoncollagenous proteins

  • Osteocalcin;

  • Bone sialoprotein;

  • They are classified as mineralized tissue-spacific, because they are found in all the calciffied connective tissies.


A third group of noncollagenous proteins
A third group of structures that originatenoncollagenous proteins

  • They are sinthesized by odontoblasts;

  • They are:

    • Osteopontin;

    • Osteonectin.


Pr edentin
Pr structures that originateedentin

  • Newly secreted dentin is unmineralized and is called predentin;

  • It is easily identified in haematoxylin and eosin stained section since it stains less intensely then dentin;

  • It is usually 10-47 micrometers and lines the innermost region of the dentin;

  • It is unmineralized and consists of collagen, glycoproteins and proteoglycans;

  • It is similar to osteoid in bone and is thickest when dentinogenesis is occurring.


Mantle predentin
Mantle predentin structures that originate

  • As the odontoblasts continue to increase in size, they also produce smaller collagen type I fibrils that orient themselves parallel to the future dentinoenamel junction;

  • In this way a layer of mantel predentin appears.


The first stage is formation of mantle dentin
The first stage is formation of mantle dentin: structures that originate

  • Its means the deposition of matrix which is composed of collagen fibers in a ground substance rich in glycosaminoglycans.

  • The fibers known as Von Korff`s fibers are argyrophilic.

  • Subodontoblasts may be responsible for a proportion of the very first matrix including the von Korff`s fibers.

  • Odontoblasts form the major part of mantle dentin matrix.


P rymary dentin
P structures that originaterymary dentin

  • Whereas mantle dentin forms from the preexisting ground substance of the dental papilla, primary dentin forms through a different process;

  • Odontoblasts increase in size, eliminating the availability of any extracellular resources to contribute to an organic matrix for mineralization;

  • Additionally, the larger odontoblasts cause collagen to be secreted in smaller amounts, which results in more tightly arranged, heterogeneous nucleation that is used for mineralization;

  • Other materials (such as lipids, phosphoproteins, and phospholipids) are also secreted.


M ineralized dentine matrix
M structures that originateineralized dentine matrix


First loyer of mantle dentin
First loyer of mantle dentin structures that originate


Cellular activity in the germ centers
Cellular activity structures that originatein the germ centers


Odontoblasts and subodontoblasts1
Odontoblasts structures that originateandsubodontoblasts


Mineralization
Mineralization structures that originate

  • The mineral phase first appears within the matrix vesicles as single crystals believed to be seeded by phospholipids present in the vesicle membrane;

  • The crystals grow rapidly and rupture from the confines if the vesicle to spread as a cluster of crystallites that fuse with adjacent clusters to form a continuous layer of mineralized matrix.


Early mineralization of the dentin matrix
Early structures that originatemineralization of thedentinmatrix


New free space exempted from the odontoblasts for a new layer of dentin
New free structures that originate space exempted from the odontoblasts for a new layer of dentin


Pattern of mineralization
Pattern of Mineralization structures that originate

  • Two patterns of mineralization can be observed, that seems to depend on the rate of dentin formation:

    • Globular calcification;

    • Linear calcification.


Globular mineralization
Globular structures that originatemineralization

  • It involves the deposition of crystals in several discrete areas of matrix by heterogeneous capture in collagen;

  • With continued crystal enlarge and eventually fuse to form a single calcified mass;

  • The pattern of mineralization is best seen in the mineralization foci that grow and coalesce;


Mineralization in circumpulpal dentin
Mineralization in circumpulpal dentin structures that originate

  • It can progress in a globular or linear pattern;

  • The size of the globules seems to depend on the rate of dentin deposition:

    • When the rate of deposition is fastest, with largest globules occurring;

    • When the rate of formation progresses slowly, the mineralization front appears none uniform and the process is said to be linear.


V structures that originateastzone

Subodonto-blast

predentin

odontoblast


The structures that originatetwodirection of dentinformation – spreadsdownthecuspslopeasfarascervicalloop, anddentinthickenes


A odontoblasts b predntin c ameloblasts d enamel e predntin
A – structures that originateodontoblasts; B- predntin; C – ameloblasts; D – enamel; E – predntin.


Vascular supply of the odontoblasts
Vascular Supply of the odontoblasts structures that originate


Life cycle of odontoblasts
Life cycle of structures that originateodontoblasts

  • There are only 3 stages in the life cycle of odontoblasts:

  • 1. Differentiating stage;

  • 2. Formation stage;

  • 3. Quiescent stage.


Differentiating stage
Differentiating stage structures that originate


Formative stage
Formative stage: structures that originate

  • Concentration of the cell organelles, granular components and globular elements;

  • Production of the first amount of dentin (dentin matrix);

  • The odontoblasts retreat from the basement membrane;

  • Leaving a single process which become enclosed in the dentinal tubule (tomes fiber;.

  • With successive deposition of dentin, tubule and process grow in length.


Quiescent stage
Quiescent stage: structures that originate

  • Actively secreting odontoblasts decrease slightly in size.

  • The odontoblastic process stop to elongate;

  • In this stage the odontoblasts produce only secondary dentin.


Stages of dentin formation and types of dentin

Stages of dentin formation and types of dentin structures that originate

Dentin is formed throughout the life of the tooth if the tooth pulp is alive


Dontoblasts predentin c dental pulp d dentin
А – structures that originateОdontoblasts; В – Predentin; C – Dentalpulp; D – Dentin.


Primary dentin
Primary dentin structures that originate

  • Primary dentin, the most prominent dentin in the tooth, lies between the enamel and the pulp chamber;

  • The outer layer closest to enamel is known as mantle dentin. This layer is unique to the rest of primary dentin;

  • Mantle dentin is formed by newly differentiated odontoblasts and forms a layer approximately 150 micrometers wide. It is a more mineralized dentin;

  • Below it lies the circumpulpal dentin, a less mineralized dentin which makes up most of the dentin layer and is secreted after the mantle dentin by the odontoblasts.


Predentin dentin odontoblasts
Predentin structures that originate, Dentin, Odontoblasts

Dentin

Predentin

Dentinal

tubules

Odontoblasts


Secondary and tertiary d entin
Secondary structures that originateand Tertiary Dentin

  • Secondary dentin is formed after root formation is finished and occurs at a much slower rate. It is not formed at a uniform rate along the tooth, but instead forms faster along sections closer to the crown of a tooth;

  • This development continues throughout life and accounts for the smaller areas of pulp found in older individuals;

  • Tertiary dentin, also known as reparative dentin, forms in reaction to stimuli, such as attrition or dental caries.


Dentinogenesis primary dentin secondary dentin
Dentinogenesis structures that originate; Primary dentin; Secondarydentin;


Secondary dentin regular secondary dentin
Secondary dentin (Regular Secondary Dentin) structures that originate

  • Secondary dentin is formed after root formation is complete, normally after the tooth has erupted and is functional. It grows much slower than primary dentin, but maintains its incremental aspect of growth;

  • It has a similar structure to primary dentin, although its deposition is not always even around the pulp chamber. It is the growth of this dentin that causes the decrease in the size of the pulp chamber with age.


Tertiary dentin irregular secondary dentin or reparative dentin
Tertiary dentin (Irregular Secondary Dentin or Reparative Dentin)

  • Tertiary dentin is dentin formed as a reaction to external insult such as caries. It is of two types:

    • reactionary, where dentin is formed from a pre-existing odontoblast;

    • or reparative, where newly differentiated odontoblast-like cells are formed due to the death of the original odontoblasts, from a pulpal progenitor cells.

  • Tertiary dentin is only formed by an odontoblast directly affected by stimulus.


Tertiary Dentin)dentin.


Composition of dentin
Composition of dentin Dentin)

  • Organic substance:

    • 30-25%  from its weight;

    • About 90% collagen fibers:

    • About 10% ground substance:

  • Inorganic substance:

    • 70-75% from its weight:

    • Hydroxyapatite crystallites.


Properties of dentin
Properties of dentin Dentin)

  • Yellowish in color;

  • Elastic;

  • Less hard than enamel, but more than cementum;

  • Less radio-opaque than enamel, but more than cementum;

  • 3-10 mm thick.


Dentin1
Dentin Dentin)

  • Dentin is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth.

  • Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp.

  • By weight, 70% of dentin consists of the mineral hydroxylapatite, 20% is organic material and 10% is water;

  • Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel;

  • Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel.


Types of dentin
Types of Dentin Dentin)

  • Mantle dentin;

  • Interglobular dentin;

  • Circumpulpal dentin;

  • Predentin.


Mantle dentin
Mantle dentin Dentin)

  • The most superficial layer of dentin;

  • The most highly mineralized;

    • This is due to:

      • Predominance of Korff`s fibers;

      • They are properly arranged in parallel;

      • This helps in tightly arrangement of crystals;

      • There are at least intercrystal spaces;

      • There are at least organic matter.


Mantle dentin1
Mantle dentin Dentin)

  • The most highly mineralized dentin;

  • It is similar in degree of mineralization of enamel;


Mantle dentin2
Mantle Dentin Dentin)

  • It is situated just below the dentinoenamel junction;

  • There odonto-blast processes lose their curve.


Branches of odontoblasts
Branches Dentin) of Odontoblasts

  • At DEJ odontoblasts branch out;

  • In the lower sections of dentin, they are united in one main branch;

  • On the surface, go out a greater number of processes than leave from the pulp.


Curvature of the dentinal tubules
Curvature of the dentinal tubules Dentin)

  • A – neonatale line;

  • B – Mantle dentin;

  • C – circumpulpal dentin;

  • D - S-shaped primary curvateure of the dentinal tubules in human crown dentin;

  • E – DEJ.


S shaped curveture of the dentinal tubules
S-shaped Dentin)curveture of theDentinalTubules

  • A. S-shaped path curveture of the dental tubules;

  • B. DEJ;

  • C. Mantle dentin;

  • D. Circumpulpal dentin.


Dentinal tubules
Dentinal Tubules Dentin)

  • A. Odontoblasts in the dentinal tubules;

  • B. DEJ;

  • C. Enamel;

  • D. Spindles in the enamel


Spindles in the enamel
Spindles in the enamel Dentin)

  • Duringhistogenesis,part of processes were passed the DEJ to stimulate ameloblasts.


Mantle dentin3
Mantle Dentin)dentin


Circumpulpal dentin
Circumpulpal Dentin Dentin)

  • It is the thickest layer of dentin;

  • It is less mineralized than mantle dentin;

    • The collagen fibers of this dentin are thinner than mantle dentin -β-fibers;

    • The Korff`s fibers (α- fibers) are less;

    • The crystals are arranged along the fibers;

    • They are chaotically arranged and have higher intercrystal spaces.


Circumpulpal dentin1
Circumpulpal Dentin)Dentin

  • Dentinal tubules with odontoblast`s processes;




Dental branches.tubulesafterdemineralization


Interglobular dentin
Interglobular Dentin branches.

  • It is the term used to describe areas of hypomineralized dentin where globular zones of mineralization (calcospherites) have failed to fuse into a homogeneous mass within mature dentin;

  • It is seen in the circumpulpal dentin just below the mantle dentin;

  • It is a defect of mineralization and not of matrix formation;

  • The normal architectural pattern of the tubules remains unchanged, and they run uninterrupted through the interglobular areas.


Interglobular dentin1
Interglobular Dentin branches.

  • D. Circumpulpal dentin;

  • Igd – interglobular dentin;

  • e – enamel.


Hypomineralized areas between the globules termed interglobulare spaces
Hypomineralized branches.areasbetweentheglobules, termedinterglobularespaces



G reater i ncrease
G branches.reaterIncrease


Globules of mineralization
Globules of mineralization branches.

  • Globular appearance of the mineralization in dentin arising from fusion of globules of hydroxyapatite or calcospherites.


Granular layer of tomes
Granular Layer of Tomes branches.

  • When a section of root is studied, a granular-appearing layer of dentin is seen underlying the cementum that covers the root;

  • This layer is known as the granular layer of Tomes;

  • This layer is prevalent when the person has had a deficiency in vitamin D;

  • This layer is most frequently found in the first permanent molars.


Dental branches.tubulesincircumpulpaldentin

Dentaltubulesininterglobulardentin



Predentin
Predentin branches.

  • It is a band of newly formed, unmineralized matrix of dentin at the pulpal border of the dentin;

  • Predentin is evidencethat dentin forms in two stages:

    • First – the organic matrix is deposited;

    • Second – an inorganic mineral substance is added;

  • During primary dentin formation, 4µm of predentin is deposited and calcified each day;

  • After occlusion and function, this activity decreases to 1.0 to 1.5 µm per day;


Predentin1
Predentin branches.

  • A – Odontoblasts in the pulp;

  • B - Predentin;

  • C- Dental pulp;

  • D - Dentin


Predentin the b oundary of mineralization with a globuls of mineralization
В – branches.Predentin; С –The boundaryof mineralizationwith a globuls of mineralization.


Predentin2
Predentin branches.


Incremental lines
Incremental branches.lines

  • All dentin is deposited incrementally, which means that as a certain amount of matrix is deposited daily, a hesitation in activity follows;

  • Thishesitationinformationresultsinanalteration of thematrixknownasincrementallines, orlines of vonEbner;

  • Prenatal dentin and postnatal dentin are separated by an accentuated contour line known as the neonatal line and reflects the disturbance in mineralization created by the physiological trauma of birth.


Countour lines of owen
Countour branches.lines of Owen (А)

  • Another type of incremental pattern found in dentin is the contour lines of Owen;

  • They are known as caused by accentuated deficiencies in mineralization;

  • These are recognized in longitudinal ground sections;


Incremental lines or lines of von ebner
Incremental lines, or branches.lines of von Ebner;

  • This incremental lines run at right angles to dentinal tubules and generally mark the normal rhythmic, linear pattern of dentin deposition;

  • The 5-day increment can be seen readily in conventional and ground sections, situated about 20µm apart.


Histology of dentin
Histology of Dentin branches.

  • When the dentin is viewed microscopically, several structural features can be identified:

    • Dentinal tubules;

    • Peritubular dentin;

    • Intertubular dentin.


Longitudinal ground section of dentin
Longitudinal ground section of dentin branches.

  • (A) – Intertubulardentin

  • (B) – peritubulardentin;

  • Odontoblastprocessesincanalicules, calledtubules (C).



  • The fibrils run fibrils, that outline the future dentinal tubule;circumferentially and perpendicular to the process;



Dentin fibrils, that outline the future dentinal tubule;tubulesandodontoblasts


Cross section of dentin dentinal tubules intertubular dentin peritubular dentin
Cross section of dentin fibrils, that outline the future dentinal tubule;Dentinal tubules(С); Intertubular dentin (В); peritubular dentin(А).


Inter and peritubular dentin
Inter- and peritubular dentin fibrils, that outline the future dentinal tubule;


Dentinal tubules1
Dentinal tubules fibrils, that outline the future dentinal tubule;


C fibrils, that outline the future dentinal tubule;ollagenmatrix of dentin

Dentintubules


D fibrils, that outline the future dentinal tubule;entintubuleswithodontoblastprocessesandtheirbranches


Properties of dentin1
Properties of dentin fibrils, that outline the future dentinal tubule;

  • The inorganic component - dentin is composed of 87% inorganic hydroxyapatite crystals, fluorapatite and carbonatapatite in the form of small plates;

  • Organic component - 13% collagen fibers with small amounts of other proteins and water;

    • Collagen is mainly typ I with small amounts of type III and V;

    • There are fractional inclusions of lipids and noncollagenous proteins;

    • The noncollagenous matrix proteins pack the space between collagen fibrils and accumulate along the periphery of dentinal tubules;

    • Thay comprise the following:

      • Dentin phosphoprotein – phosphophoryn, dentin sialoprotein, dentin matrix protein 1, osteonectin, osteocalcin, bone sialoprotein, osteopontin, proteoglycans and ect.


Physiology of denti n
Physiology of denti fibrils, that outline the future dentinal tubule;n

  • Metabolism in dentin is ensured by the pulp;

  • Metabolism is performed by odontoblast processes;


Odontoblasts1
Odontoblasts fibrils, that outline the future dentinal tubule;

  • They form a layer lining the periphery of the pulp and have a process extending in the dentin;

  • The number of dental tubules with odontoblasts are of 59 000 to 76 000 per square millimeeter in a coronal dentin;


Nerve endings around odontoblasts in the predentin
Nerve endings around fibrils, that outline the future dentinal tubule;odontoblastsinthepredentin


Functions o f the odontoblasts
Functions fibrils, that outline the future dentinal tubule;of the odontoblasts

  • During dentinogenesis:

    • 1Synthesisingfunction:

      • Odontoblastat synthesized proteins, matrix macromolecules and collagen;

    • 2Secreting function:

      • Odontoblasts secreted Β-fibers (collagen) and amorphous organic and inorganic matter;

    • 3. Both structurise and mineralisedentinal matrix.

  • During functional stage odontoblasts:

    • 1.Continued formative function;

    • 2.Ensure the exchange of thedentin;

    • 3. Providing a link betweenenamel, dentinanddentalpulp;

    • 5. They provide sensitivity of the

      dentin;

    • 5. They have protective function;

      • Reparativedentin;

      • Scleroticdentin;

      • Secondaryandtertiarydentinogenesis.


Physiologic secondary dentinogenesis
Physiologic fibrils, that outline the future dentinal tubule;SecondaryDentinogenesis

  • It represents the slower-paced deposition of dentin matrix that continues after completion of the crown and root of the tooth and spans a lifetime;

  • While secondary dentin is deposited all around the periphery of the tooth, its distribution is asymmetric, with greater amounts on the floor and roof of the pulp chamber.


Terciary dentinogenesis
Terciary fibrils, that outline the future dentinal tubule;Dentinogenesis

  • It describes the focal secretion of dentin in response to external influences (dental caries, tooth wear, trauma, and other tissue injury;

  • Tertiary dentin encompasses a broad spectrum of responses:

    • Regular tertiary dentin;

    • Displastic atubular dentin;

    • Reactionary dentin;

    • Reparative dentin.


Atubular dentin: areas without tubules fibrils, that outline the future dentinal tubule;


Types of secondary dentin fibrils, that outline the future dentinal tubule;

Regular

Line of demarcation:

stain dark

Clinically:

The increase of the dentin thickness and the closure of the pulp

horns make it much less possible to expose the pulp chamber during preparation.

Irregular

Line of demarcation:

stain dark

Clinically:

Functions as a barrier against caries.


Physiologic regular secondary dentin fibrils, that outline the future dentinal tubule;

The size of the pulp cavity decreases and obliteration of the pulp horns.

The course of the dentin canals is more irregular.


Osteodentin: The odontoblasts (cells) are included fibrils, that outline the future dentinal tubule;

in the formed dentin


Circumpulpal fibrils, that outline the future dentinal tubule; dentin

Response dentin


Reparative dentin an d incorrect course of dentinal tubules
Reparative fibrils, that outline the future dentinal tubule;dentinand incorrect course of dentinal tubules


Reactionary dentin
Reactionary fibrils, that outline the future dentinal tubule;dentin

  • Is defined as a tertiary dentin matrix secreted by surviving postmitotic odontoblast cells in responce to an appropriate stimuls;

  • Such a responce will be made to milder stimuli and represents up-regulation of the secretory activity of the existing odontoblast responsible for primary dentin secretion.


Reparative dentin
Reparative dentin fibrils, that outline the future dentinal tubule;


Reparative dentin1
Reparative fibrils, that outline the future dentinal tubule;dentin

Is defined as a tertiary dentin matrix secreted by a new generation of odontoblast-like cells in response to an appropriate stimuls after the death of the original postmitotic odontoblsts responsible for primary and fisyologic secondary dentin secretion;

Such a response will be made to stronger stimuli and represents a much more complex sequence of biologic processes.


Reparative dentin2
Reparative dentin fibrils, that outline the future dentinal tubule;


Репаративен дентин fibrils, that outline the future dentinal tubule;


Sclerotic dentin
Sclerotic fibrils, that outline the future dentinal tubule;Dentin

  • Sclerotic dentin describes dentinal tubules that have become occluded with calcified material;

  • When this occurs in several tubules in the same area, the dentin assumes a glossy appearance and becomes translucent;

  • This is deposition of mineral within the tubule without any dentin formation and diffuse mineralization is occurs with a viable odontoblast process still present;

  • Because sclerosis reduces the permeability of dentin, it may help to prolong pulp vitality.


Dead tracts
Dead fibrils, that outline the future dentinal tubule;tracts

  • Loss a tubular contents (odontoblast processes) results in dead tracts, wich indicate air in the tubules;

  • Below the dead tract area is sclerotic dentin, wich protect the pulp from bacteria or bacterial products.


Dead tracts in the dentin
Dead fibrils, that outline the future dentinal tubule;tractsinthedentin


Vitality and sensitivity of dentin
Vitality and sensitivity of dentin fibrils, that outline the future dentinal tubule;

  • Vitality of dentin is its ability to react following physiological or pathological stimuli.

  • Forming secondary or tertiary dentin, feeling pain are signs of being vital;

  • Several theories have been cited to explain the mechanism involved in dentinal sensitivity & vitality:

    • The transducer theory,

    • the conduction theory,

    • the modulation theory

    • the Brännström's hydrodynamic theory.


The transducer theory
The transducer theory fibrils, that outline the future dentinal tubule;

  • The transducer theory contend that the odontoblast and its process are capable to mediate neural impulse in the same way as nerve cells;

  • Contra:

  • But investigations have proved that no pain is experienced in exposed dentin by application of substance known to bare nerve endings.

  • The measurement of membrane potential of the odontoblasts shows clearly that this potential is very low to contribute in the pain excitation.


The conduction theory
The conduction theory fibrils, that outline the future dentinal tubule;

The conduction theory (intratubularinnervation theory) contend that dentin is richly innervated and those nerves mediate the impulse to the brain.

Some new studies show that predentin and the first layer of circumpulpal dentin (0.2mm) is innervated with nerve fiber from the raschkows plexus.

The fibers run parallel to the tomes fiber in the dentin tubules.

The density of those fiber is much higher in the coronal dentin than cervical dentin. Root dentin doesn’t include such fibers.



The conduction theory can not be seen in histological slides.


The hydrodynamic theory
The hydrodynamic theory can not be seen in histological slides.

The “hydrodynamic theory”, developed in the 1960’s is the widely accepted physiopathological theory of Dentin Sensitivity.

Temperature, physical osmotic changes or electrical and chemical stimuli and dehydration are the most pain-inducing stimuli.

According to this theory, those stimuli increase centrifugal fluid flow within the dentinal tubules, giving rise to a pressure change throughout the entire dentine.

The movement stimulates intradentinal nerve

receptors sensitive to pressure (BARORECEPTORS),

which leads to the transmission of the stimuli .

This simulation generates pain.


The hydrodynamic theory1
The hydrodynamic theory can not be seen in histological slides.

Berman describes this reaction as: “The coefficient of thermal expansion of the tubule fluid is about ten times that of the tubule wall.

Therefore, heat applied to dentin will result in expansion of the fluid and cold will result in contraction of the fluid, both creating an excitation of the 'mechano-receptor'.”


Appearance of a pain in the dentin
Appearance of a pain can not be seen in histological slides. inthedentin

The fluid moves through the tubules and excites nerves

The incentives on dentine causes movement of fluid in the tubules


include hot and cold, tactile, evaporative, and osmotic, can not be seen in histological slides.