Histology of the tooth: mature dentin and pulp

Dental papilla

What forms dentin and pulp developmentally

As one unit

How do dentin and pulp function together?

Into the dentinal tubule

Where does each odontoblasts extend a long cell process?

Covered by enamel in crown and cementum in root

What is dentin covered by that makes it not exposed

Crystalline material

What type of material is mature dentin?

Less hard than enamel, but slightly harder than bone

Is dentin harder than enamel or bone?

Enamel

What does dentin form a resilient support for?

-70% in organic/mineralized material (hydroxyapatite crystals)

-20% organic material

-10% water

What is dentin made up of?

Continues to form throughout the life of a tooth

Why is dentin a vital tissue?

Yes

Can damaged dentin be repaired

The dentin of the tooth is seen through the translucency of the overlying enamel

What gives the enamel crown it's underlying yellow tone

The differences in the mineralization levels of different parts of the tooth

-dentin appears more radio lucent because it is less dense or more radiopaque then pulp

What can be noted regarding dentin on a radiograph

-Odontoblast process

-dentinal fluid

-Nerve fiber

What three things do the dentinal tubules contain

Extend from the DEJ in crown or DCJ in route to the dentin-predentin junction

Where do the dentinal tubules extend?

Tapered contour

The large diameter of dental tubules closer to the pulp

Canaliculi

The tiny canals that connect adjacent tubules

The pathway taken by the odontoblast during oppositional growth of predentin

The direction of the tubule reflects what

Primary and secondary

What are the two types of curvature that the dentinal tubules show?

Primary curvature

The curvature of dentinal tubules that reflects the overall tubule course overtime, which resembles a large S shaped curve in crown

Secondary curvature

The curvature of dentinal tubules that consists of small delicate curves noted in the primary curvature, reflecting the smaller daily changes in odontoblast direction during apposition; branching noted near DEJ

Odontoblast process

Long cellular extension that extends from the odontoblast cell body into the dentinal tubule; has numerous side branches

In the pulp along its outer wall

Where do the cell bodies of the odontoblasts reside in

Not all the way to DEJ or DCJ

Where will you find mature dentin odontoblast processes

Via their side branches within canaliculi

How do you adjacent cell processes contact

From cell body towards DEJ/DCJ

Where does the odontoblast process taper from

Incremental (imbrication) lines of von Ebner

Daily incremental growth lines in the dentin structure; linear structure going vertically

The amount of dentin deposited over a period of 24 hours

What does the distance between successive lines of von Ebner represent?

-4um in crown

-6um in root

What is the distance between successive lines of von Ebner in the crown and root?

Cross striations in enamel

What are the incremental lines of von ebner similar to?

Contour lines of owen

Wider thickened incremental lines that represent the metabolic disturbance occurring during apposition that affects the odontoblasts

Stria of Retzius in enamel

What are the contour lines of owen similar to?

Neonatal line

Accent accentuated, contour line of owen that represents sudden physiological change occurring during birth

Tomes granular layer

A granular appearing layer just beneath the cementum that probably represents cut end of looped terminal portions of dentinal tubules DCJ

peritubular/intratubular dentin

The type of dentin that creates the wall of the dentinal tubule; highly mineralized dentin (more calcified); few collagen fibrils

Intertubular dentin

All dentin located between the dentinal tubules- majority of dentin; less mineralized than intratubular dentin

Type I

What type of collagen fibrils are found in the matrix of intertubular dentin

Mantle dentin

The first formed layer of crown and root dentin; nearest to DEJ/DCJ

Consist of both type III (Von Korff's fibers) and type I collagen

What type of collagen does mantle dentin consist of

Collagen fibers larger and oriented perpendicular to DEJ

How are the collagen fibers oriented in mantle dentin

Circumpulpal dentin

Remainder of dentin situated underneath the mantle dentin and formed after mantle dentin

Type I; smaller in diameter and more randomly oriented

What type of collagen fibers are in circumpulpal dentin

Predentin

A layer of newly secreted organic matrix that is always present between odontoblasts and mineralized dentin

Unmineralized; similar to osteoid in bone

Is predentin mineralized or unmineralized? Similar to what

Primary dentin

Dentin formed before the completion of the apical foramen of the root

Apical foramen

The opening of the dental pulp into the surrounding periodontal ligament near the apex of the tooth

Secondary dentin

Dentin formed after the completion of the apical foramen of the root

More slowly

At what pace does the secondary dentin form compared to primary dentin?

Along entire pulp-dentin border

Where does secondary dentin form

Throughout the life of the tooth

How long does the secondary dentin continue to form

A sharp change in direction of dentinal tubule

What characterizes the junction between 1° and 2° dentin

Tertiary dentin

Dentin formed in response to localized injury, which exposes the dentinal tubules to oral environment; localized, rapid formation of dentin

On pulpal surface underneath secondary dentin only at sites corresponding to areas of stimulation; where tubule is exposed

Where is tertiary dentin deposited?

Seals off tubules from pulp

What does the tertiary dentin do that prevent bacteria from entering the pulp?

Reactive and reparative dentin

What are the two types of tertiary dentin?

Reactive dentin

The type of tertiary dentin formed by pre-existing or original odontoblasts; newly formed tubules, continuous with those of secondary dentin

Reparative dentin

The type of tertiary dentin formed by newly differentiated odontoblasts; pre-existing dentinal tubules discontinuous

Calcospherites

Spherical foci of hydroxyapatite crystals

Globular dentin

The type of dentin where calcospherites are fused together; appears as rounded areas

At the mineralization front

Where can globular dentin be found?

Interglobular dentin

The type of dentin where calcospherites are not fused; less mineralized; appears as a regular, dark, arc like areas

In the circumpulpal dentin just beneath the mantle dentin

Where is interglobular dentin found

Pass right through them

What do the dentinal tubules do regarding the interglobular dentin

Dead tract dentin

Tract of dentin containing empty tubules

Dead tract dentin

Dentin that forms when odontoblasts either killed or injured the processes retracted, leaves empty dentinal tubules; acute response from trauma

Air

What fills the dentinal tubules during histological processing of dead tract dentin

Appears black

What does dead tract dentin look like under a microscope?

Sclerotic dentin

The area of dentin containing dentinal tubules completely occluded with minerals; slower response to chronic trauma; cause progression of intratubular dentin

Transparent

What does sclerotic dentin look like under a microscope?

Dentin Hypersensitivity

What occurs when dentin (the dentinal tubules) is exposed as a result of caries, cavity preparation, gingival recession, or attrition

It is a type of diffused pain

Why is dentin hypersensitivity difficult to localize for a dental professional and patient

Dentin Hypersensitivity

Extreme sensitivity of pulp-dentin complex

Mechanical, thermal, and tactile stimuli to the dentin

What is perceived as pain in dentin hypersensitivity

Bradykinin and histamine

What two products produce pain in other tissues, but not in dentin

-nerves in dentin

-odontoblast as receptor

-hydrodynamic theory

What are the three theories of dentin hypersensitivity

Nerves in dentin

The theory of dentin hypersensitivity where 1 in 10 tubes contain a free nerve ending

odontoblast as receptor

The theory of dentin hypersensitivity where nerves shown to synapse on odontoblast cell body

Hydrodynamic theory

The theory of dentin hypersensitivity where there is fluid movement through dentinal tubules; most plausible theory

Evaporation and loss of dentinal fluid, etc.

In the hydrodynamic theory for dentin hypersensitivity, what are the causes of fluid movement?

-decrease volume of pulp as secondary dentin forms

-May lead to true pulp stones

What are the two age changes of secondary dentin

Decreased volume of pulp as tertiary forms

What is an age change of tertiary dentin?

Sclerotic dentin and dead tract dentin

What are the other two types of dentin that form with age

Pulp

A loose connective tissue; only soft tissue of the tooth; derived from the dental papilla

-formation

-nutrition

-Defense

-sensation

-reparative

What are the five functions of pulp?

Throughout life of tooth

How long does the dental pulp form?

-coronal pulp: located in the coronal pulp chamber and pulp horns

-radicular pulp: located in root canals

What two types of pulp are within the pulp chamber? What are they?

Apical foramen

The opening from the pulp into the surrounding periodontal ligament near the Apex of the tooth where nerves, blood vessels and lymphatic vessels enter and exit the pulp from PDL

Accessory (lateral) canals

The connection between pulp and PDL that forms during root development

4

How many pulp zones are there?

Odontoblastic layer

The outermost pulp zone layer against dentin

Between the cells

Where are the dentinal nerve fibers located in the odontoblastic

Cell free zone

The pulp zone that has fewer cells; capillary and nerve plexus (subodontoblastic plexus of Raschkow)

Cell-rich zone

The pulp zone that has increased cell density mainly of fibroblasts; more extensive vascularity

Pulp core or central zone

The central most region of pulp; numerous cell types, nerves, and blood vessels, and lymphatic vessels

-fibroblasts: most numerous

-odontoblasts: next numerous

-undifferentiated mesenchymal cells

-macrophages

-T-lymphocytes

What are the five cell types of pulp? Most numerous?

Amorphus ground substance (AGS), collagen and reticular fibers

What is the extracellular material of pulp

YES (well vascularized)

Does pulp have blood vessels

-myelinated/unmyelinated nerve fibers

-unmyelinated nerve and nerve endings present in dentinal tubules

What are the two characteristics of the nerve supply of pulp?

Pulp stones

Denticles that form in dental pulp

-True or false

-free, attached, or embedded

What are the two types of pulp stones and what are the three types of locations that they can be?

True pulp stones

The type of pulp stone that is an ectopic (abnormal) mass of dentin in pulp made of odontoblasts and dentinal tubules