Tooth Pulp

Oral Physiology

Dr. Maria Eller Isabel T. Collantes

Parts of the tooth

Enamel Dentine Pulp

Periodontal Tissue

Gingivae Alveolar Bone Cementum Periodontal Ligament

Enamel

Outer most layer of the crown

The hardest tissue in the body

DENTIN

The second layer of the crown

Generally light yellow in colour

Its colour determines the overall colour of the tooth

There are many microscopic tubules inside the dentine which connect to the pulp.

Dentin

Pulp

Fluid Nerve Fibers

Odontoblast Cell

Periodontal tissues

Gingiva

Alveolar bone

Cementum

Periodontal Ligament

GINGIVA

The fibrous investing tissue covered by keratinized epithelium

The gingiva is one of the soft tissues that line the oral cavity

All the soft tissue in the mouth are Known as the oral mucosa

Gingiva

ALVEOLAR BONE

Also called the “alveolar process”

the thickened ridge of bone containing the tooth sockets in the mandible and maxilla.

Alveolar bone

PERIODONTAL LIGAMENT

Connects the cementum of the tooth root to the alveolar bone of the socket.

Periodontal Ligament

CEMENTUM

Bonelike rigid connective tissue

covering the root of a tooth from the cementoenamel junction to the apex and lining the apex of the root canal

It also serves as an attachment structure for the periodontal ligament, thus assisting in tooth support.

Cementum

• Formation of dentine (dentinogenesis)• Sensation (pain only?)• First line of defense to injuries and

infection of dentin• Tertiary dentin• Immuno-competent• Clearance of toxic substances

Functions of dental pulp

PULP

Innermost part of the tooth

Highly vascular and richly-innervated connective tissue forming the soft core of the tooth

Pulp

Consist of fibers (collagen), cells (odontoblasts, fibroblasts, undifferentiated mesenchymal cells), and a matrix (proteoglycans and fibronectin)

Encapsulated and protected by hard tissue walls

Very low compliance because the surrounding dentin prevents any significant volume changes if the pressure within the pulp chamber changes

Pulp

Contains large number of free nerve endings

Afferent neurons originating from the maxillary or mandibular division of the trigeminal nerve

Pulp

four distinct zones1. odontoblastic zone

at the periphery2. cell-free zone of

Weil – below the ODs3. cell-rich zone4. pulp core – major

vessels and nerves

Predentin

Odontoblasts

Cell-free zone

Cell-rich zone

Cell bodies

Odontoblasticprocess

Dentin

Predentin

Odontoblasts layer

Cell free zone

Cell rich zone

Pulp core

Odontoblastic layer

Lines the outer pulpal wall and consists of the cell bodies of odontoblast

Secondary dentin may form in this area from the apposition of odontoblast.

Cell Free zone

Fewer cells than odontoblastic layer Nerve and Capillary plexus is located

here

Cell Rich Zone

Increased density of as compared to cell free zone

More extensive vascular system

Pulpal core

Center of the pulp chamber Many cells Extensive vascular supply Similar to cell rich zone

Cells in the pulp

odontoblast Fibroblast Mesenchymal cells Macrophages Lymphocytes Dendritic cells

Pulp

Odontoblasts line the periphery of the pulp

chamber columnar in the crown region

of the fully developed tooth more cuboidal at the midpoint

of the pulp chamber the morphology reflects their

activity – the more active the more elongated they are – with more cytoplasm

Odontoblast

active ODs within the pulp have prominent organelles with multiple vesicles

CN pathway is similar to that of the pulp fibroblasts

CNs and non-CN proteins are packaged into secretory granules for exocytosis

the non-CN proteins are the same as those found in the dentin

Fibroblasts

greatest number numerous in the coronal

portion of the pulp form the cell-rich zone form and maintain the pulp

matrix – CN fibers and ground substance

in young pulp the fibroblasts are active and have extensive cytoplasm and organelles

decrease in size with age and they flatten

Mesenchymal cells

undifferentiated cells of the pulp

from neural crest (ectodermal)

depending on the stimulus – give rise to the ODs or fibroblasts of the pulp

Vascularity and Nerves of the Vascularity and Nerves of the PulpPulp

The pulp organ is extensively vascular

with vessels arising from the external

carotids to the superior or inferior alveolar

arteries. It drain by the same vein.

Blood flow is more rapid in the pulp than

in most area of the body, and the blood

pressure is quite high

The walls of the pulpal vessels

become very thin as their enter the

pulp.

Nerves : Several large nerves enter

the apical canal of each Molar and

Premolar and single ones enter the

anterior teeth. This trunks transverse

the radicular pulp, proceed to the

coronal area and branch peripherally.

Nerves and Vessels of the pulp

• Blood and vessels enter and

exit the dental pulp by way of

the apical and accessory

foramina

• Pulp is richly innervated;

nerves enter the pulp through

the apical foramen, along with

afferent blood vessels and

together form the neuro-

vascular bundle

Nerves in pulpNerves in pulp

Dental PulpDental Pulp

Nerve Blood vessel

Subodontoblastic zone – is a major site of nutrient and gas exchange within the subodontoblastic plexus

In a healthy tooth pulp, blood occupies about 5% of the total volume

High blood flow comparable to the brain and liver

Blood flow is controlled by autonomic nervous system primarily by sympathetic efferent nerve fibres

Activity in nociceptive afferents can also influence pulpal blood flow by the release of vasodilatatory substances

Extravasation – it is a leakage of plasma proteins from venules to the insterstitial space and that will be an inflammation, thus increases intrapulpal pressure

Inflammation of the pulp is induced by bacterial or mechanical trauma and can lead to increases in pressure in the pulp chamber

Increased pressure will lead to tissue hypoxia then necrosis

Types and properties of pulpal sensory nerve fibers

A – beta fibers A – delta fibers C – fibers Non – myelinated sympathetic fibers

A-beta fibers

Conduction velocity 30-70 m/sVery low threshold, non-

noxious sensation50% of myelinated fibers in pulpFunctions not fully known

A – delta fibers

Conduction velocity 2-30 m/s Lower threshold Involved in fast, sharp pain Stimulated by hydrodynamic stimuli Sensitive to ischemia Sharp pain

C - fibers

Conduction velocity 0-2 m/s Higher threshold Involved in slow, dull pain Stimulated by direct pulp damage Sensitive to anesthetics Dull pain

Non – myelinated sympathetic fibers

Conduction velocity 0-2 m/sPost-ganglionic fibers of

superior cervical ganglionVasoconstriction

Possible mechanisms of dentine sensitivity

Hydrodynamic mechanism(Gysi, 1900; Brannstrom, 1963)

Neural Theory

Attributes activation to excitation of the nerve endings within the dentinal tubules, leading to action potentials that are conducted along the parent primary afferent nerve fibres in the pulp into the dental nerve branches and then to the brain

Odontoblastic transduction theory Proposes that the stimuli initially excite the

odontoblast process or body, the membrane of which may come into close apposition with that of the nerve endings in the pulp or in the dentinal tubule

The odontoblast then transmits the excitation to the associated nerve endings

However, lack of evidence for either synapses or neurotransmission between odontoblast and dentinal nerve opposes this theory

Hydrodynamic theory

Proposes that the stimuli cause displacement of the fluid within the dentinal tubules

Stimuli such as drilling of dentin, probing, and air drying of exposed dentin, mechanical irritation of pulp, and application of hyperosmotic solutions promote liquid displacement within the dentinal tubules

Displacement occurs in either an outward or an inward direction

Activate mechanoreceptors in the nerve endings in the dentin or pulp

Clinical correlatesTOOTHACHE It is a clinical manifestation of tooth pulp

physiology Perceived only a limited number of forms Intensity very close to the threshold of pain

can induce a non painful sensation called “pre pain”

Pre pain or paraesthesia may be due to recruitment of a few nociceptive afferent fibres, but not enough to give the pain sensation