P1-ENDO-CHAPTER 12

Odontoblast

represent a crucial element in this PULP DENTIN COMPLEX

periphery of the pulp tissue

Location of odontoblast

dental pulp

It is dependent on the protection provided by the dentin and enamel

○ Impacts on dentin may affect the pulpal components

○ Disturbances in the dental pulp will affect the quantity and quality of the dentin produced

Integrated dynamics of the pulp–dentin complex imply

Odontoblast Layer

The outermost stratum of cells of the healthy pulp

subjacent to the predentin

location of Odontoblast Layer

Odontoblast processes

pass through the predentin into the inner part of dentin

cell bodies of odontoblasts

The odontoblast layer is composed of the

Capillaries

nerve fibers

dendritic cells

found among the odontoblasts

tall columnar

In the coronal portion of a young pulp actively secreting collagen, odontoblasts are

coronal portion of a young pulp

In the ______ actively secreting collagen, odontoblasts are tall columnar

staggered

Odontoblasts vary in height, so their nuclei are

palisade appearance

arrangement of odontoblast in coronal pulp

three to five cells thick

odontoblast later appears to have ______ although there is only one actual layer

30–40 nm wide

Intercellular spaces between odontoblasts are

Tight junctions

Gap junctional complexes

Odontoblast cell bodies are connected by:

Gap junctions

They are formed by connexin proteins, allowing cell-to-cell passage of signal molecules

more cells per unit area

The odontoblast layer in the coronal pulp contains ____ than the radicular pulp

columnar

Mature coronal pulp odontoblasts are usually

cuboidal

midportion of the radicular pulp, odontoblasts are

squamous layer of flattened cells

Near the apical foramen, odontoblasts appear as a

less crowded odontoblast cell bodies

Fewer dentinal tubules per unit area in the root result in

narrowing of the pulp space

During maturation and aging, continued crowding occurs due to

Apoptosis of odontoblasts

adjusts for limited space during development

○ Desmosomes (zonula adherens)

○ Gap junctions (nexuses)

○ Tight junctions (zonula occludens

Specialized cell-to-cell junctions include

Desmosomes

zonula adherens

Gap junctions

nexuses

Tight junctions

zonula occludens

Spot desmosomes

in the apical part of odontoblast cell bodies mechanically join odontoblasts

Gap junctions

allow passage of signal molecules to synchronize secretory activit

predentin layers

Gap junctions help produce uniform

formation of primary dentin

Gap junctions are numeorus during

subodontoblastic area

Gap junctions and desmosomes also join odontoblasts to fibroblast processes in the

Tight junctions

are mainly found in the apical part of odontoblasts in young teeth

linear ridges and grooves

Tight junction sonsist of _____ that close off the intercellular space

Tracer studies

show passage of small elements between odontoblasts from subodontoblastic capillaries to predentin and dentin

permeability of the odontoblast layer

Tight junctions determine

passage of molecules, ions, and fluid

Tight junctions retrict the _______ between pulp and predentin

cavity preparation

During _____ these tight junctions are disrupted, increasing dentin permeability

Cell-Poor Zone

Immediately subjacent to the odontoblast layer in the coronal pulp

40 µm inwidth

Cell-Poor Zone is a narrow zone approximately

Cell-Poor Zone

Relatively free of cells

cell-free layer of Weil

other name for Cell-Poor Zone

Blood capillaries

○ Unmyelinated nerve fibers

○ Slender cytoplasmic processes of fibroblasts

contents of Cell-poor zone

functional status of the pulp

The presence or absence of the cell-poor zone depends on

young pylp

older pulp

Cell-poor zone is not apparent in

young pulp

where dentin forms rapidly

older pulp

reparative dentin is being produced

Cell-Rich Zone

Located in the subodontoblastic area

fibroblasts

Cell-Rich Zone Contains a relatively high proportion of___ than central pulp

coronal pulp

Cell-rich zone is e prominent in the

● Fibroblasts

● Immune cells: macrophages and dendritic cells

● Undifferentiated mesenchymal stem cells

cellular components of cell-rich zone

peripheral migration of cells

Cell rich zone forms due to ______from the central pulp around tooth eruption

immunocompetent cells

Migration of ______ occurs in and out of the cell-rich zone in response to antigenic challenge

antigenic challenge

Migration of immunocompetent cells occurs in and out of the cell-rich zone in response to

Odontoblast death

triggers increased mitosis

Irreversibly injured odontoblasts

are replaced by cells migrating from the cell-rich zone onto the inner dentin surface

TRUE

Odontoblast death is the first step in forming a new odontoblast layer T/F

Stem cells

are a source for replacement odontoblasts

Pulp Proper

e central mass of the pulp

loose connective tissue

Pulp Proper is consist of

larger blood vessels and nerves

Pulp proper contains what

Fibroblast

most prominent cell in Pulp Proper

Odontoblast

Most characteristic and specialized cell of the dentin-pulp complex

Odontoblast

Responsible for dentinogenesis during tooth development and aging

Odontoblast

Forms dentin and dentinal tubules, making dentin a living responsive tissue

Produce a matrix of collagen fibrils, noncollagenous proteins, and proteoglycans capable of mineralization

Similarities with osteoblasts and cementoblasts

Highly ordered RER

■ Prominent Golgi complex

■ Secretory granules

■ Numerous mitochondria

■ Rich in RNA, nuclei with prominent nucleoli

Ultrastructural features of osteoblasts and cementoblasts

: tall columnar cells

Odontoblast in coronal pulp

Osteoblasts/Cementoblasts:

polygonal to cuboidal

osteocytes/cementocytes

Osteoblasts/cementoblasts may become _____ within the matrix

dentinal tubule

Odontoblast leaves a cellular process forming the_____ ; cell body remains outside mineralized tissue

canaliculi

Lateral branches of odontoblast processes interconnect through _____, allowing intercellular communication and fluid/metabolite circulation through the matrix

intercellular communication

fluid/metabolite circulation

Lateral branches of odontoblast processes interconnect through canaliculi, allowing _____and ____ through the matrix

four nucleoli

Active Odontoblast cell body contains large nucleus, up to

centrally located, smooth-walled vesicles and cisternae

Active Odontoblast golgi complex

evenly distributed throughout cytoplasm

Active Odontoblast mitochondiria

closely stacked cisternae, with ribosomes for protein synthesis

Active Odontoblast RER

Collagen

Proteoglycans

Dentin sialoprotein

Phosphophoryn

Enzymes

Secretory products of odontoblast

Type 1

Collage mainly in Odontoblast

Type V

least collagen in Odontoblast

Phosphophoryn

highly phosphorylated, unique to dentin, involved in extracellular mineralization

Acid phosphatase

Alkaline phosphatase

Enzymes in Odontoblast

Acid phosphatase:

lysosomal, may digest resorbed predentin matrix

Alkaline phosphatase

linked to mineralization, precise role in dentinogenesis unclear

Resting/Inactive Odontoblast

Decreased number of organelles

Resting/Inactive Odontoblast

May become shorter

root development and eruption

Resting/Inactive Odontoblast changes begin after _____, as dentin production shifts from primary to secondary dentin

Macrophage

Monocytes that leave the bloodstream, enter tissues, and differentiate into various subpopulations

Subpopulations

can be identified by antigenic properties in immunohistochemical studies

close to blood vessels

Location of Macrophage

■ Removes extravasated red blood cells

■ Removes dead cells

■ Removes foreign bodies

Macrophage is active in scavening by

lysosomal enzymes

Ingested material is destroyed by

memory T cells

Marchophage Processes antigen and presents it to

class II MHC molecules

Antigen bound to ____ interacts with naïve or memory T cell receptors

pulp signaling pathways

Similar to fibroblasts, macrophages participate in

■ Interleukin 1

■ Tumor necrosis factor (TNF)

■ Growth factors

■ Other cytokines

Marchophages When activated by inflammatory stimuli, produc

lymphatic markers

Subset of macrophages express

Dendritic Cell

Accessory cells of the immune system

epidermis and mucous membranes

Dendritic Cell found in _____ as Langerhan’s cell