Opy notes (pulp)

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 zones
1. odontoblastic zone at the periphery
2. cell-free zone of Weil – below the ODs
3. cell-rich zone
4. pulp core – major vessels and nerves

Predentin Odontoblasts Cell-free zone Cell-rich zone Cell bodies Odontoblastic process

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 Pulp
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 pulp

Dental 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/s
Very low threshold , non-noxious sensation
50% of myelinated fibers in pulp
Functions not fully known

A – delta fibers
Lower threshold
Involved in fast, sharp pain
Stimulated by hydrodynamic stimuli
Sensitive to ischemia
Sharp pain

C - fibers
Higher threshold
Involved in slow, dull pain
Stimulated by direct pulp damage
Sensitive to anesthetic s
Dull pain

Non – myelinated sympathetic fibers
Post-ganglionic fibers of superior cervical ganglion
Vasoconstriction

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 correlates TOOTHACHE
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

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