18. Dentine-Pulp Complex Flashcards
Define ‘dental pulp’
connective tissue derived from mesenchymal cells of dental papilla
2 types of dental pulp
- coronal pulp
- radicular pulp
Apical foramen and accessory canals are entry for …
- blood vessels for nourishment
- nerves for sensation
- lymphatic vessels for lymph drainage
Dental pulp is … connective tissue made of …
- loose
- extracellular matrix
- diff cell types
- blood and lymphatic vessels
- nerves
Dental pulp is …% water and …% organic material
Does this ever change?
- 75, 25
- changes in development (dental papilla to dental pulp) and varies between tooth types
Is there hard tissue in dental pulp?
- none in normal pulp
- calcifications and pulp stones occur in aged teeth
How different is pulp structure in primary and permanent teeth?
similar
- 4 zones in each
4 histological zones in pulp
- odontoblast cell layer
- cell-free zone
- cell-rich zone
- pulp core
Odontoblast cell layer contain what kind of cell?
- odontoblasts
What’s within the cell-free zone?
- few cells
- mainly extracellular matrix
- nerve endings
What’s within the cell rich zone?
many cells
- mainly fibroblasts
What’s within the pulp core?
- central tissue
- nerves
- blood vessels
From innermost of pulp to outermost, order the layers
- cell rich zone
- cell free zone
- odontoblast layer
- predentin
- mineralization layer
Cells within pulp
- odontoblasts
- fibroblasts
- undifferentiated mesenchymal cells
- stem cells
- defence cells
Coronal odontoblasts are … and have what features?
- columnar
- cellular process into dentinal tubule
- more cuboidal in root
Odontoblasts produce what? and for how long?
- dentine (predentine)
- present throughout life of tooth
As the tooth matures, what happens to odontoblast layer of pulp?
- becomes flatter
- number of cells reduced by apoptosis
- secondary dentine laid at slow rate
- reduces size of pulp
How does the odontoblast layer of pulp respond to external stimuli?
- odontoblast-like cells can differentiate from progenitor cells in pulp
- produces tertiary dentine
3 types of junctions between odontoblasts
- tight
- desmosomes
- gap
Role of tight junctions and desmosomes in odontoblasts
- maintains spacial relationships
- restricts substances in pulp from entering dentine
Role of gap junctions in odontoblasts
- openings allow exchange of small molecules and cell-to-cell communications
What is the most abundant cell type in dental pulp?
fibroblasts
Role of fibroblasts
- produce collagen fibres and ground substance in pulp matrix
- degrade collagen for collagen turnover
Explain cellular differences in fibroblasts in young and old pulp
- in young, large centrally located nucleus with multiple cellular processes
- in aged, smaller, spindle shaped fibroblasts with fewer organelles
Role of undifferentiated mesenchymal cells
- differentiate into odontoblast-like cells and fibroblasts
- number reduces with age
Role of dental pulp stem cells
- multipotent
- can differentiate into odontoblasts, chondrocytes, osteoblasts, adipocytes and neurons
Types and role of immune cells in dental pulp
- macrophages patrol pulp and remove dead cells/bacteria with role in inflammation
- T and B lymphocytes in adaptive/antibody driven immune system
- neutrophils and eosinophils respond to infection and mediate inflammation
- dendritic cells present foreign antigens to T cells
What collagen is present in extracellular matrix of pulp?
- type 1 and 3
- forms a scaffold providing stability to pulp
What’s in the ground substance/non-fibrous protein matrix of pulp?
- glycosaminoglycans, proteoglycans, glycoproteins and water
- hydrophilic molecules that swell when hydrated forming hydrogels that fill most of EC space
Role of ground substance in extracellular matrix of pulp
- resevoir for growth factors and other bioactive molecules
- act as medium for transport and movement of nutrients/metabolites
- regulates various cellular processes like proliferation, differentiation and migration
Explain vascular supply of pulp
- blood vessels originating in periodontal ligament enter pulp via apical foramen
- peripheral blood vessels branch out towards odontoblast layer and form small capillaries
Explain lymphatic drainage of pulp?
- drain tissue fluid
- thinner walls than blood vessels and have no red blood cells
Around … nerve axons enter apical foramen
2500
Of the nerve axons coming through the apical foramen, 25% are … and 75% are …
- myelinated afferent nerve fibres
- unmyelinated C fibres
Explain myelinated afferent nerve fibres in teeth
- Schwann cells (form myelin sheath)
- transit pain sensation to CNS
- cell bodies in trigeminal ganglion
Explain unmyelinated C fibres in teeth
- mainly devoid of Schwann cell covering
- can sense changes in extracellular environment
- afferent fibres (main) terminate at odontoblast layer or in dental tubules to transmit noxious stimuli (pain)
- efferent fibres (minor) terminate on smooth muscle cells of arterioles to regulate capillary flow
Explain the Plexus of Raschkow
- extensive nerve plexus that terminates in the cell free zone just below the odontoblast layer of crown
- no nerve plexus in root canals
- some axons pass between odontoblasts and sometimes enter dental tubules
- most nerve bundles terminate as free, unmyelinated nerve endings
Function of the dental pulp
- provide vitality to the tooth
- nourishment of odontoblasts and other pulp cells via blood vessels/capillaries
- protection with sensation of external stimuli (thermal, mechanical, chemical) via nerves/endings and barrier/defence (reaction to ext stimuli produces tertiary dentine and activation of immune system if inflamed)
Changes in pulp chamber with age
- young teeth have large pulp chamber
- old teeth have very narrow pulp chamber and root canals
How do the challenges for dentists change with young and old pulp chambers?
- in young, the large chamber is a challenge for cavity/crown prep as it has a thin dentine layer and pulp exposure can occur easily
- in old it challenges root canal treatment
How is caries a spread of infection?
- from dental pulp into surrounding periodontal tissues
- causes periodontal abscess
How is periodontal disease spread?
- from surrounding periodontal tissues into dental pulp
- e.g through accessory root canals
Where are accessory root canals?
- can occur anywhere in the root
- mainly at root apex
What’s an common cause of root canal treatment?
- failure to notice and clean accessory root canals
- causes persistant infection
Procedure of root canal
- infected tooth
- drill an opening
- fill and clear
- finish off
Collagen fibres are more towards … so it’s easier to do a pulpectomy from …
- tooth apex
- apical region
Define ‘diffuse calcifications or pulp stones’
- calcified masses can be formed in pulp
- as a response to chronic stimulus (caries infection etc) or age related change
How do pulp stones occur?
- older pulp becomes less vascular and can form diffuse calcifications
- false pulp stones formed from calcifying blood vessels and contain bone-like material (organised in concentric rings)
- true pulp stones fromed from detached odontoblasts and contain dentine
- pulp stones attached to dentine or remain free in pulp
Afferent nerve endings terminate where?
- in dentine/near odontoblasts
Afferent nerve endings sense?
- pain
- mechanical
- chemical
- thermal
stimuli
3 theories for dentine sensitivity
- neural
- odontoblasts as receptors
- hydrodynamic
Explain neural dentine sensitivity
- dentine is directly innervated
- but not many nerve endings are detected in dentine
Explain odontoblasts as receptors dentine sensitivity
- odontoblasts act as receptors
- form synaptic contacts with nerve endings
Explain hydrodynamic theory
- fluid movement in dentinal tubules is sensed directly or indirectly by nerve endings
What is thought to increase sensory capacity?
branching of odontoblast processes at EDJ
