Endodontium

Question 1

What is the odontoblast layer and what is its function

Answer 1

Permeability barrier between the pulp and dentine tubules

Regulates exchange of materials between the pulp and the ECF

Question 2

Describe the exchange of materials from the pulp to dentine

Answer 2

Nutrients to sustain cells
Calcium and phosphates for formation of 2* and 3* dentine
Na2+ and K+ for action potentials

Question 3

Describe the exchange of materials from dentine to the pulp

Answer 3

Medicaments applied to dentine
Components from filling materials
Toxins produced from bacteria in carious lesions

Question 4

Describe the anatomy of the pulp nerves

Answer 4

Branches of alveolar nerves enter the pulp via the apical foramen
Pass along root canal in the centre of the pulp towards the coronal pulp chamber
Branches out in the sub-odontoblastic layer to form Raschow’s plexus
Terminal branches enter odontoblastic layer and some nerves enter dentinal tubules

Question 5

What proportion of dentine tubules contain nerves

Answer 5

Under cusps 40% of tubules contain nerves
15% in coronal dentine
4% in root dentine

Question 6

Describe the hydrodynamic mechanism

Answer 6

Stimulus acts on open tubules causing an increased rate of dentinal fluid flow
This generates APs in intra-dental nerves
The APs pass to the brain to cause pain

Question 7

What is the purpose of the hydrodynamic mechanism

Answer 7

For activating intradental sensory nerves to cause pain

Question 8

What are the hydrodynamic effects of outward fluid flow

Answer 8

Cooling
Drying, evaporation
Hypertonic solutions
Decreased hydrostatic pressure

Question 9

What are the hydrodynamic effects of inwards fluid flow

Answer 9

Heating
Mechanical pressure
Increased hydrostatic pressure

Question 10

What type of fluid flow is more effective in activating intradental nerves and why

Answer 10

Outward flow as it stretches the nerves and causes greater stimuli

Question 11

Which stimuli have nothing to do with dentinal fluid and how do these stimuli work

Answer 11

Intense heating
Intense cooling
Electrical current
Pain-producing chemicals
These act directly on intradental nerves

Question 12

How can high fillings cause dentinal pain

Answer 12

The inlays and onlay restorations will be distorted by occlusal forces and generate pressure to alter the flow of the fluids

Question 13

How are Ab and As fibre intradental nerves activated and what do they cause

Answer 13

Activated by hydrodynamic stimuli applied to dentine

Responsible for the normal dentine sensitivity

Question 14

How are C fibre intradental nerves activated and what do they cause

Answer 14

Activated directly by stimuli rather than the hydrodynamic mechanism
Respond to most forms of intense stimulation
Mediate pain associated with pulp inflammation - caries

Question 15

What factors control pulp blood flow

Answer 15

Local factors - metabolites
Nerves
Circulating hormones
Drugs

Question 16

How do nerves control pulp blood flow

Answer 16

Sympathetic - controls flow by changing diameter of blood vessels, generates vasoconstriction, reducing blood flow
Somatic afferent peptidergic - sensory fibres that when stimulated, release peptides (substance P) which cause vasodilation, increasing blood flow

Question 17

How do circulating hormones control pulp blood flow

Answer 17

Adrenaline promotes vasoconstriction

Question 18

How can drugs control pulp blood flow

Answer 18

Vasoconstrictors such as adrenaline and felypressin are used in local anaesthetics

Question 19

What type of drilling can cause irreversible pulpal damage

Answer 19

An uncooled bur with high speed motor

Question 20

What are the functions of pulp nerves

Answer 20

Sensory - mediate pain
Sympathetic and afferent - control pulp blood flow
Promote neurogenic inflammation and induce inflammation
Promote dentine formation
Facilitate the immune response

Question 21

Describe the pulps neurogenic effect on inflammation

Answer 21

Afferent sensory fibres are stimulated by changes in dentinal fluid flow, causing the release of vasoactive and immune active peptides
These promote vasodilation and increase vascular permeability causing increased pulp tissue pressure
This will increase tubular fluid flow

Question 22

What is a pulpitis

Answer 22

Acute inflammation in the dental pulp

Question 23

Describe the events of a pulpitis

Answer 23

The pulp cannot swell as it is confined within the pulp chamber
Oedema causes in increase in pulp pressure
This can have effects on blood flow and nerve excitability
This incapacitated the tissues to perform their function

Question 24

What is the immediate dentine-pulp response to injury

Answer 24

Nociceptor activation triggers pain

Question 25

What is the dentine-pulp response to injury after 1 minute

Answer 25

Early inflammatory response
Kinins, prostaglandins and neuropeptides
Vasodilation

Question 26

What is the dentine-pulp response to injury after 10 minutes

Answer 26

Nociceptor sensitisation
Extravasian of fluid and oedema causing increase in tissue pressure
Presence of neutrophils, basophils and eosinophils

Question 27

What is the dentine-pulp response to injury after 100 minutes

Answer 27

Enzyme activation - indicates the initial phase of dentinogenesis
Presence of nerve growth factor
Monocytes present indicating cell-mediated immunity

Question 28

What is the dentine-pulp response to injury after 1 day

Answer 28

Nerve sprouting (NGF)
Increased atonal transport
Altered excitability of the CNS synapses

Question 29

What is the dentine-pulp response to injury after 1 week

Answer 29

Resulting effects of dentinogenesis with repair and tertiary dentine formation