Pulp Morphology Flashcards
What tissue is the pulp?
Connective tissue
What cells are present in the pulp?
Odontoblasts, fibroblasts, defence cells
What are the extra cellular components (fibres/matrix) of the pulp that make up the ECM?
Fibres - oxytalan, collagen
Matrix - proteoglycans, chondroitin SO4, dermatan SO4
What is present in the pulp?
Cells
Extracellular components
Nerves (autonomic (sympathetic))
Lymphatics
Blood vessels
Where does pulp open up to the external environment?
At the apex of the root
What is non-mineralised dentine called?
Pre-dentine
What type of dentine is closest to the pulp?
Pre-dentine
What are the functions of the pulp?
Nutrition (blood vessels)
Dentine growth (primary/secondary)
Dentine repair (tertiary)
Defence (immune cells, lymphatics)
Neural (sensory-pain, control of dentinogenesis)
What are the type of links between dentine and pulp?
Developmental
Structural
Functional
What are the developmental links between dentine and pulp?
Both dentine and pulp develop from the dental papilla which originates from ectomesenchyme cells
What are the structural links between dentine and pulp?
Elements from the pulp extend into dentine such as:
Odontoblast processes
Nerve terminals
Immune cells (dendritic cells)
Dentinal fluid
What is never found in normal dentine?
Blood vessels
Where is the origin of fluid in the pulp from?
Fluid leaks from the pulp blood capillaries into the interstitial space
What are the systems that controls the flow of fluid within vessels?
Haemodynamics
Hydrodynamics
Where does the fluid in the interstitial space go?
Some drained by lymphatics in the pulp
Some passes along the dentinal tubules (dentinal fluid)
What is the flow of the fluid proportional to?
Proportional to the pressure inside the pulp
What are the functional links between dentine and pulp?
Formation of secondary dentine
Formation of tertiary dentine in response to trauma
Exchange of material between the pulp and dentine
What are the types of tertiary dentine?
Reactionary dentine
Reparative dentine
What is the difference between the two types of tertiary dentine?
Reactionary dentine is laid down in response to mild stimulus by primary odontoblasts
Reparative dentine is laid down - in response to intense stimulus that destroys the primary odontoblasts - by secondary odontoblasts
Which type of dentine is formed slower?
Secondary throughout life
What can cause tooth wear?
Mastication (abrasion)
Bruxism (attrition)
Abfraction (caused by occlusal overload)
Diet (erosion)
Operative procedures (cavity cutting, crown preparation)
Where does abfraction cause tooth-wear?
Fractures in the cervical region of enamel
Besides producing dentine, what do odontoblasts form?
A permeable barrier between pulp and dentinal tubules - to regulate exchange of materials between pulp and tubular extracellular fluid
How does the movement occur between the pulp and dentinal tubules?
In both directions
What does the pulp pass to the dentine?
Nutrients (to sustain cells)
Formation of secondary and tertiary dentine (mineralisation)
Ions for nerve terminals (K+, Na+)
What does the dentine pass to the pulp?
Medicaments applied to dentine (for treatment)
Toxins from bacteria, and components of filling materials
What cranial nerve supplies the teeth?
Trigeminal 5
Where do the alveolar nerves come from and where do they enter?
Branches of the alveolar nerves come from the maxillary and mandibular branches of the trigeminal. They enter the pulp of the tooth via the apical foramen
How do the alveolar nerves pass?
Via the root canal in the centre of the pulp towards the coronal pulp chamber
Where do the alveolar nerves fan out?
Fan out in the sub-odontoblastic layer and form the plexus of raschow
What plexus do the branches of the alveolar nerves form?
Plexus of Raschow
After the plexus, where do the branches enter?
Terminal branches enter the odontoblast layer and some will enter the dentinal tubules
How many tubules contain nerves under the cusp?
40%
How long can the axons extend? (Circa)
100-200 micrometers
What percentage of coronal dentine is tubularly innervated?
15%
What percentage of root dentine is tubularly innervated?
4%
Where do most axons end up?
Pulp-predentine region
What are the types of possible stimulus that can affect dentine and therefore the pulp?
Thermal
Mechanical
Evaporative
Chemical
What are the steps of the hydrodynamic mechanism? (For activating interdental sensory nerves)
Stimulus applied to open tubules (exposed dentine)
Rate of dentinal fluid flow increased
Generation of AP in intra-dentinal nerves
APs passed to brain and cause pain
What type of stimulus produces an outward flow of dentinal fluid?
decreased hydrostatic pressure
cooling, drying, evaporation, hypertonic solutions
What type of stimulus produces an inward flow of dentinal fluid?
increased hydrostatic pressure
heating, mechanical
What direction of flow causes a greater neural stimulus?
Outwards (away from the pulp)
What stimuli bypass the hydrodynamic mechanism and have a direct effect on intradental nerves?
Intense heating/ cooling
Electrical current
Pain-producing chemicals
What iatrogenic factor can cause dentinal pain and how?
High fillings
Distorted by occlusal forces therefore generating pressure to alter flow of fluid
What nerve fibres are responsible for normal dentinal sensitivity?
A-beta and A-delta myelinated fibres
What are these fibres activated by? (normal dentinal sensitivity)
Activated by hydrodynamic stimuli applied to dentine
What are the type of fibres that mediate pain associated with pain inflammation?
C fibres (unmyelinated)
What are c-fibres activated by?
By direct intense stimuli, rather than hydrodynamic mechanism
Where does blood supply of the teeth come from?
Branches of the maxillary artery
What does cavity preparation without cooling increase?
Inflammation therefore vascular permeability (increased hydrodynamic mechanism)
What is the methods of control of pulp blood flow?
Local factors (metabolites)
Nerves (sympathetic, somatic afferents peptidergic - release peptides while receiving stimulation)
Circulating hormones (adrenaline)
Drugs (vasoconstrictors in LA)
What is the function of pulp nerves?
Sensory - mediates pain
Control of blood vessels
Promote neurogenic inflammation -neuropeptides, subst P, CGRP
Promote dentine formation
(MAYBE) Facilitate immune response
How does the neurogenic effect of inflammation occur?
Afferent sensorial fibres are stimulated by changes in fluid flow (hydrodynamic),
Triggers axon reflex which releases vasoactive peptides (substance P and CGRP)
Peptides promote vasodilation and vascular permeability which increase pulp tissue pressure
The pressure further increases tubular fluid flow
What are the pulp responses to injury from immediate to 10 minutes?
Immediate - nociceptor activation (pain)
After 1 minute - early inflammatory response
After 10 minutes - nociceptor sensitisation (increased activity)
What happens in the early inflammatory response (1 minute)?
Kinins, prostaglandins, neuropeptides,
Vasodilation
What happens during nociceptor sensitisation (10 minutes)?
Extravasating of fluid (Oedema)
Polymorphonuclear cell migration (leukocytes)
What happens after 100 minutes?
Enzyme activation (nerve growth factor, initial phases of dentinogenesis)
Monocyte presence
What happens after 24 hours?
Nerve sprouting (response to growth factor)
Increased axonal transport
Altered excitability of CNS synapses
What happens after a week?
Repair; tertiary dentine formation through dentinogenesis
What happens long term?
Variable rate of repair and recovery depending on size of lesion, host response,
What is pulpitis?
Acute inflammation of the dental pulp
Why does pulpitis differ from other inflammation?
Pulp cannot swell as it is confined within the pulp chamber which causes increase in pulp pressure. Which has an effect on blood flow and nerve excitability.
