Dentinepulp complex Flashcards
The dental pulp is known as the connective tissue ____ of the tooth?
- Core
What cells are found in the pulp?
- Odontoblasts = produce dentine
- Fibroblasts = produce collagen
- Defence cells
What are the extracellular components of the pulp?
- Fibres = collagen, oxytalan
- Matrix; proteoglycans, chonfroitin SO4, dermatan SO4
What nerves are found in the pulp?
- Sensory; autonomic (sympathetic)
Are blood vessels and lymphatics found in the blood?
- Yes
What are the functions of the dental pulp? (5 points)
- Nutritive - blood vessels
- Dentine growth (primary, secondary)
- Dentine repair (tertiary)
- Defence (immune cells; lymphatics)
- Neural
= Sensory - pain
= Control of dentinogenesis
What is dentinogenesis?
- The process of dentine formation in the development of teeth
There are close links between dentine and pulp. What are some of these likes? (3 points)
- Developmental links
- Structural links
- Functional links
What is the developmental link between dentine and pulp?
- Dentine and pulp develop from the dental papilla
What are the structural links between dentine and pulp?
Pulpal elements extend into dentine:
- Odontoblast process
- Nerve terminals
- Immune cells (dendritic cels)
- Dentinal fluid
Note: no blood vessels in normal dentine so any bleeding in the cavity means you are inside the pulp
What is meant by haemodynamics?
- Related to the flow of blood within the organs and tissues of the body
What is meant by hydrodynamics?
- Forces acting or exerted by fluids
What are the functional links between dentine and pulp? (3 points)
- Formation of secondary dentine (once tooth is fully formed)
- Formation of tertiary dentine in response to tooth wear (or trauma) (and be reactionary or reparative dentine)
- Regulate exchange of material between dentine and pulp
What is reactionary dentine?
- Formed in response to a carious decay, to excessive abrasion, or to the cytotoxic effects of monomers released by a restorative material. This is how the pulp limits undesirable noxious effects
What is reparative dentine?
- Same as tertiary dentine
- Formed in response to trauma/irritant
What are different things that can cause tooth wear in enamel and dentine? (6 points)
- Mastication (abrasion)
- Bruxism (attrition)
- Abfraction (occlusal overload -> fractures and cervical lesions)
- Diet (erosion)
- Caries
- Operative procedures
What is abrasion?
Loss of tooth substance caused by abnormal rubbing of a non-dental object
What is attrition?
- The loss of tooth substance caused by contact between occluding surfaces
- Caused by parafunctional rather than functional activity
What is bruxism?
- (parafunction) purposeless clenching or grinding of the teeth
What is erosion?
- The loss of tooth substance by a chemical process (acid) not involving bacterial action - diet, regurgitation, environmental
What is Abfraction?
- pathological loss of tooth structure owing to biomechanical forces (flexion, compression or tension) or chemical degradation; it is most visible as v-shaped notches in the cervical area of a tooth
When is primary dentine laid down?
Laid down first and quicker throughout the development of the tooth
When is secondary dentine laid down?
- Laid down later and slower (formed once tooth has fully developed)
What id reactionary dentine laid down in response to?
- In response to a mild stimulus
- Might create a reaction of the dentine-pulp process to produce dentine = this is tertiary dentine
What type of cells is reactionary dentine laid down by?
- Primary odontoblasts
What is reparative dentine laid down in response to?
- In response to intense stimulus that destroys the primary odontoblasts
What type of cells lay down reparative dentine?
- Secondary odontoblasts
Is tertiary dentine an organised or unorganised structure?
- Disorganised matrix
What is tertiary dentine laid down in response to?
- In response to stimulation
The odontoblasts layer can be seen as a permeability barrier. What does it separate?
- The pulp and the tubular space
The odontoblasts layer can be seen as a permeability barrier. What does it regulate the movement of?
- Material between the pulp and tubular ECF
- Movement may be in either direction
There is an exchange of materials between the dentine and pulp. What is exchanged from pulp -> dentine? (3 points)
- Nutrients, to sustain cells
- Formation of secondary and tertiary dentine
- Function of tubular nerves (e.g. K+ - potassium is important to provide the membrane potential of those nerves to generate the action potential
There is an exchange of materials between the dentine and pulp. What is exchanged from dentine -> pulp? (2 points)
- Medicaments applied to dentine
- Diffusion of ‘toxins’, from bacteria, components of filling materials
What are the pulp nerves?
- Branches of alveolar nerves
Where do the neuromuscular bundles enter the pulp?
- Via the apical foramen and pass along the root canal in the centre of the pulp towards the coronal pulp chamber
- The pulp cavity terminates at the root apex as a small opening called the apical foramen
The branches of alveolar nerves in the pulp fan out in the sub-odontoblastic layer - What is this called?
- The Raschow’s plexus
What is the Raschow’s plexus?
- A plexus of myelinated nerve fibres located between the core of the pulp of the tooth and the cell-rich zone, axons of Raschow plexus loose their myelin sheath (but not their schwann cells) as they penetrate the cell rich and cell free zones to make synaptic contact with the odontoblast cell body in the pulp or odontoblastic process within the dentinal tubule; Raschow plexus is responsible for transmitting pain sensation from the pulp of the tooth
Which type of branches of nerves enter the odontoblastic layer of the pulp?
Terminal branches
Some nerves from the pulp will enter into the dentine near the pulp. What percentage of tubules under the cusps contain nerves?
40%
What distance from the pulp have intratubular nerve fibres been found?
- Some axons extend from around 100-200micrometers from the pulp but have not been found further than this
Some nerves from the pulp will enter into the dentine near the pulp. What percentage of tubules in coronal dentine contain nerves?
15%
Some nerves from the pulp will enter into the dentine near the pulp. What percentage of tubules in root dentine contain nerves?
4%
Few axons from the pulp enter the dentinal tubules, where do most of them end?
- In the pulp-predentin region
What is the hydrodynamic mechanism for activating intradental sensory nerves in the pulp? (5 points)
- Have a stimulus e.g. thermal, mechanical, evaporative or chemical
- This acts on exposed dentine; open tubules
- This increases the rate of dentinal fluid flow
- There is a generation of action potentials in intra-dental nerves
- Action potentials pass to the brain which causes pain
What can the outward flow of dentinal fluid from the pulp be caused by? (5 points)
- Cooling
- Drying
- Evaporating
- Hypertonic solutions
- Decreased hydrostatic pressure
What can the inward flow of dentinal fluid to the pulp be caused by? (3 points)
- Heating
- Mechanical
- Increased hydrostatic pressure
Is inward or outward fluid flow more effective in activating intradental nerves, causing pain?
- Outward flow
- Rapid, outward flow stretches the nerves
Some stimuli bypass the hydrodynamic mechanism and act directly on intradental nerves, what are these? (4 points)
- Intense heating
- Intense cooling
- Electric current
- Pain-producing chemicals
Which type of filling can be a cause of dental pain due to the force distorting the dentine and altering the tubular fluid flow?
- ‘high’ fillings
What are the different types of nerve found in the pulp? (3 points)
- A-beta and A-delta fibres
- C fibres
Are A-beta and A-delta fibres that are found in pulp myelinated or unmyelinated?
- Large and small myelinated
Are the C-fibres that are found in pulp myelinated or unmyelinated?
- Unmyelinated
What are A-beta and A-delta fibres that are found in the pulp activated by?
- Hydro-dynamic stimuli that is applied to dentine
- (hydrodynamic is the branch of physics that is concerned with the flow of liquids)
What do A-beta and A-delta fibres found in pulp probably mediate?
- ‘normal’ dentinal sensitivity
What are C-fibres that are found in dental pulp activated by?
- Probably activated directly by stimuli, rather than hydrodynamic mechanism
- They respond to most forms of intense stimulation
What do C-fibres that are found in pulp probably mediate?
- Probably mediate pain associated with pulp inflammation (e.g. caries)
Where does the blood supply to the teeth come from?
- Branches of the maxillary artery
Do pulp blood vessels extend into dentine?
- No
- If drilling dentine and start seeing blood there is something wring as you have probably hit the pulp
If you expose pulp and there is no bleeding, is there a problem?
- Yes
What can control the blood flow in the pulp? (4 points)
- Local factors e.g. metabolites
- Nerves (sympathetic, somatic afferents)
- Circulating hormones
- Drugs e.g. LA preparations with vasoconstrictors
What are the functions of the pulp nerves? (5 points)
- Sensory - mediating pain
- Control of pulp blood vessels (sympathetic: vasoconstrictor, afferents: vasodilator)
- Promote neurogenic inflammation (neuropeptides) (important = the nerve itself can induce an inflammatory response)
- Promote dentine formation
- Facilitate the immune response (?)
What is the dentine-pulp immediate response to injury?
- Nociceptor activation - pain
What is the dentine-pulp response to injury after approx. 1 minute? (3 points)
- Early inflammatory response
- Kinins, prostaglandins, neuropeptides
- Vasodilation which will cause swelling
What is the dentine-pulp response to injury after approx. 10 minutes? (3 points)
- Nociceptor sensitisation
- Extravasation of fluid, oedema
- Polymorph migration (many nucleated leukocytes)
- Extravasation = a discharge or escape, as of blood, from a vessel into the tissues
What is extravasation?
- A discharge or escape, as of blood, from a vessel into the tissues
What is the dentine-pulp response to injury after approx. 100 minutes? (2 points)
- Enzyme activation; nerve growth factor (will facilitate the reorganisation of nerves)
- Monocyte presence
What is the dentine-pulp response to injury after approx. 1 day? (3 points)
- Nerve sprouting (NGF)
- Increased axonal transport
- Altered excitability of CNS synapses
What is the dentine-pulp response to injury after approx. 1 week? (2 points)
- Repair; tertiary dentine formation
- Variable; completion of repair and recovery (this is the situation where you have a response that is mild)
What is pulpitis?
- Acute inflammation in the dental pulp
What is the difference between inflammation in the dental pulp (pulpitis) and other tissues? (3 points)
- Similar to other tissues EXCEPT that the pulp cannot swell as it is confined within the pulp chamber
- Oedema causes an increase in pulp pressure
- This can have variable effects on blood flow and on nerve excitability
