Lesson 3.1: Pulp

How is the composition of the Pulp?

What are the main characteristics of the pulp?

• Only soft tissue of the tooth

• Formed by highly vascularized and innervated CT

• Nutritional and physical support to dentin

What are the components of the Pulp?

• Pulp cavity: Coronal portion (pulp chamber) // root portion (the root canals)

• Pulp chamber: Takes general shape of anatomical crown

• Pulp horns: Extensions of the chamber below the cusps (especially prominent below the vestibular cusp of premolar teeth and the mesiovestibular cusp of molars).

Where does the root canal end and what structures are located there?

It ends at the apical foramen, where pulp and pdl meet and major nerves and vessels enter and exit the tooth.

If there is more than one foramen present in a root, the largest is designated as the apical foramen and the others as accessory foramina.

Where is the apical foramen located in developing and developed teeth?

• Developing teeth: wide and central.

• Developed tooth: smaller and eccentric position

What are lateral canals and what are their functions?

• Connections between pulp and pdl tissues along the lateral surface

• Can act as pathways that spread disease from one tissue to another

• Diseases of the dental pulp can lead to changes in periodontal tissues. More rarely, periodontal diseases affect the dental pulp

What are the functions of the pulp?

1. Sensitive: Only tissue of the tooth with nerve fibers. Dentin pain is acute and pulp pain is dull and throbbing

2. Defense and repair: Repair at level of peritubular and tertiary dentin formation

3. Inductive: Dentin deposition is necessary for enamel synthesis to occur.

4. Formative: The pulp is essential for the formation and preservation of dentin

5. Nutritive: The pulp nourishes the dentin through the odontoblastic extensions

Where are odontoblasts located and what are their characte?

• Odontoblasts are specific cells in the inner lining of the pulp chamber.

• Their body is always in the pulp.

• Number and size varies according to type of tooth and location in the pulp:

  • In the crown larger than in the root

    • At crown: columnar

    • In the middle part: cuboid

    • Apical part: flattened

• When they differentiate, they cannot undergo further cell divison

What is the function of the odontoblasts?

To form a layer that covers the periphery of the pulp and to extend its process towards the dentin

How is the morphology of odontoblasts in active and aged ones?

Aged:

• Nucleus central

• Absent or few secretory granules

Active cell:

• Nucleus closer to base and elongated

• Golgi zone with numerous mitochondria

• Secretory granules

What are the odontoblastic processes?

• Cytoplasmic extensions of odontoblasts, which form dentin

• Abundance of microtubules and filaments arranged in a linear pattern along its length

• Presence of granules reflecting pinocytotic (endocytic) activity along the process membrane

What is inside the dentinal tubules and what is its function?

Their contents give dentin its vitality and ability to respond to various stimuli

• Odontoblastic process along entire length

• Dentinal fluid: Fills space in tubule between walls and odontoblastic process

What are the components of dentinal fluid?

• Proteoglycans

• tenascin (glycoprot.)

• Fibronectin

• Serum albumin proteins

• Heparan Sulfate (HS)

• Glycoprotein

• Transferrin

Fibroblasts

• Main cells of pulp, especially in crown

• Change in number and morphology during repair and inflammation of connective tissue

• Multifactoral cells that have the ability to degrade collagen

What are the functions of fibroblasts?

• Form, maintain and regulate the replacement of fibrillar and amorphous matrix

• Secrete precursor of collagen, reticular and elastic fibers as well as the ground substance of pulp

Difference between young and aged pulp

Young pulp:

• Increases the synthesis of matrix

• Rounded cytoplasm

• Organelles associated with synthesis and secretion are increased

• Have long plasma extensions

Aged pulps:

• Decreases matrix synthesis

• Decreases in organelles

• Flattened cells

• Transform into fibrocytes

Function of Ectomesenchymal cells in Pulp

These constitute the pulp reserve population, due to their ability to differentiate according to the stimulus

What are the types of Inflammatory cells inside the pulp?

• Macrophages: in pulp center, derived from blood, removal of dead cells

• T lymphocytes, and scarce B lymphocytes: increased in carious allowing generation of antibodies

• Leukocytes: increase when infection

• Dendritic cells: around odontoblast layer, below unerupted

What are the types of fibers in the pulp?

• Type 1 collagen: Few and irregularly arranged In crown, greater concentration in root, increases with age

• Type 3 (Reticulin): More in pulp (mesenchymal) than in dentin, create von Korff plexus including the odontoblasts

• Elastic: very scarce and located around afferent bv

• Oxytlan: Immature elastic fibers

Where is the highest concentration of collagen in pulp?

In the the most apical portion

What are the components of the ground substance?

• Glycosaminoglycans (GAGS): Chondroitin and dermatan sulfate, Hyaluronix acid, Keratan sulfate

• Proteoglycans: Versican, Decorin, Biglucan

• Water

What are the functions of the ground substance?

• Acts as a medium of nutrients from the vasculature to the cells and of waste metabolites from the cells to the vascularate

• Contributes to viscosity of matrix giving it a gelatinous character

• Alterations in its composition: metabolic changes, reduced cellular function, irregularities in mineral deposition

• Decreases with age

What are the histological layers of the pulp?

• Odontoblastic layer

• Cell-free zone of Weil

• Cell-rich zone

• Pulp core (main vessels and pulp nerves)

Odontoblastic layer

• Composed of odontoblasts

• In lateral regions gap junctions predominate, regulating exchange of low-molecular-weight metabolites and their number increases as odontoblasts mature

• Some nerve endings pass through the layer and extend into odontoblastic processes

Weils cell free zone

Poor in cells, although within this cell-free area we can find Raschkow’s nerve plexus fibroblasts, and dendritic cells.

Cell rich zone

• high cell density

• Consists mainly of mesenchymal cells and fibroblasts, which give rise to von Korffs fibers

• Cells decrease with age

Central zone

• few fibers but rich in blood vessels and nerves

• Main cell types are fibroblasts, macrophages, perivascular ectomesenchymal cells, pulp dendritic cells

Blood circulation of pulp

• Blood vessels enter pulp together with sensory and autonomic nerve fibers

• Vessel are of small caliber and metarterioles are larger

• Smooth muscle of vessel have alpha and beta adrenergic receptors that cause vasoconstriction

• In the coronary region the vessels branch and decrease in caliber and frm the subodontoblastic capillary plexus

• Blood reaching the crown is almost twice that of root region

What is the function of the blood circulation inside the pulp?

• Capillary network has the function of nourishing the odontoblasts

• These capillaries can be continuous or fenestrated

Structure of blood vessels

• Pericytes Wrapped around the endothelial wall of capillaries regulating and maintaining stability of the walls and maintenance of lamina

• Pericytes can differentiate into macrophages

• Dendritic cells next to pericytes

• Basal lamina on which endothelial cells sit acts a selective filter for the passage of macromolecules and form pulp

What is nutrition and how does the it occur?

It is the movement of metabolites through the endothelium

• Through pores of fenestrated capillaries

• Transcytosis mediated by pinocytic vesicles

Lymphatic circulation of the pulp

Vessels can be found in the central part of the pulp and, although less, also in the odontoblastic zone. These vessels leave the pulp together with the blood vessels and nerves

How is the lymphatic circulation in the different teeth?

• Anterior lower teeth: submental lymph nodes

• Anterior and posterior upper teeth: submandibular and deep cervical lymph nodes

What are the types of fibers that innervate the pulp?

1. A fibers: Myelin and larger caliber. The fastest

2. B fibers: Myelin but medium caliber

3. C fibers: Without mylein and of small caliber

Innervation of Pulp

• Tissue very rich in nerve fibers

• Follows same part as afferent vessel: begin as large nerve bundles that arborize peripherally as they are extend occlusally through the pulp core

Innervation in root and crown

• Crown: Subodontoblastic plexus of raschkow: an extensive plexus of nerves in the zone free of weil cells below bodies of odontoblasts

• Root: No plexus. The branches come out of the ascending trunks and become arborized. Each branch supplies its own territory

What are the types of innervation?

Autonomic and senory

Autonomic innervation

Sympathetic C fibers (efferent)

• Axons originate from superior cervical ganglion and attach to the anterior musculature

• Slow conduction fibers are involved in the control of arteriolar caliber (Vasomotor function)

• Neurotransmitter is catecholamine

Parasympathetic C fibers

• Contain acetylcholine and vasoactive intestinal protein (VIP) contribute to vasodilation by release of nitric oxide

Sensory innervation

Type A myelin fibers - Fast

• Fast driving fibers

• Distributed in peripheral zone of pulp

• Penetrate the odontoblastic prolongations creating synapses (Raschkow plexus)

• Respond to hydrodynamic, tactile, osmotic or thermal stimuli

• Transmit the sensation of acute and well localized pain

Type A delta fibers

• Responsible for pain conduction

• Mature after 4-5 years of occlusion

C-unmylelinated fibers

• Slow

• Distributed generally in internal zone of pulp

• Respond to bradykinin and histamine stimuli, but not to hydrodynamic+

• Produce sensation of pain that is not very localized and prolonged in time as in inflammatory processes

Age related changes and response to environmental stimuli

• Pulp volume reduction

• Decrease in irrigation and innervation

• Gradual decrease of cell population of the pulp connective tissue, immature cells, immunity and response

• Transformation of the lax connective tissue of the pulp into semi-dense connective tisue

• Appearance of irregular centers of mineralization

  • Central pulp region in adult pulp formed by precipitation of mineral salts on the center of collagen matrix

  • Can be true (dentinal tubules) or false (formed by layers)