Dentine & Pulp

Question 0

What is the function of C nerve fibres in dentine?

Answer 0

Unmyelinated
Activated directly by stimuli rather than hydrodynamic mechanism
Respond to most forms of intense stimulation
Mediate pain associated with pulp inflammation e.g. caries

Question 1

What is the function of AB and AD fibres in dentine?

Answer 1

large & small myelinated
activated by hydro-dynamic stimuli applied to dentine
mediate ‘normal’ dentinal sensitivity

Question 2

What artery supplies the teeth?

Answer 2

Maxillary artery supplies both maxillary and mandibular arches through alveolar artery branches.
Blood vessels are ONLY in the pulp - they do not penetrate dentine.

Question 3

What is the function of the pulp nerves?

Answer 3

Sensory - mediate pain
Control of pulp blood vessels - sympathetic (vasoconstriction), afferents (vasodilation)
Promotes neurogenic inflammation
Promotes dentine formation

Question 4

What controls pulpal blood flow?

Answer 4

Local factors e.g. metabolites
Nerves - sympathetic, somatic afferents
Circulating hormone e.g. adrenaline
Drugs e.g. LA with vasoconstrictor

Question 5

What mechanisms are involved in the dentine-pulp response to injury?

Answer 5

Nociceptor activation - pain
Early inflammatory response
Vasodilation
Extravasation of fluid
Polymorph migration
Enzyme activation; nerve growth factor
Monocyte presence
Increased axonal transport
Altered excitability of CNS synapses
Repair; tertiary dentine formation

Question 6

How is oedema in the pulp different to how it is in other body tissues?

Answer 6

The pulp cannot swell as it’s confined within the pulp chamber.
Oedema causes increased pulp pressure which can have variable effects on blood flow and nerve excitability.

Question 7

What are the components of dental pulp?

Answer 7

Odontoblasts
Fibroblasts
Defence cells
Extracellular components - fibres, matrix
Nerves
Blood vessels
Lymphatics

Question 8

What are the developmental links between dentine and pulp?

Answer 8

Both develop from the dental papilla

Question 9

What pulpal elements extend into dentine?

Answer 9

Odontoblast processes
Nerve terminals
Immune cells (dendritic cells)
Dentinal fluid
NOT blood vessels

Question 10

What is abfraction?

Answer 10

Occlusal overload resulting in cervical fractures and lesions

Question 11

What is reactionary dentine?

Answer 11

Dentine formed in response to mild stimulus. Laid down by primary odontoblasts.

Question 12

What is reparative dentine?

Answer 12

Dentine formed in response to intense stimulus that has destroyed the primary odontoblasts. It is laid down by secondary odontoblasts recruited from the fibroblast layer.

Question 13

What material is exchanged from pulp to dentine?

Answer 13

Nutrients to sustain cells
Formation of secondary/tertiary dentine
Ions for the function of tubular nerves (e.g. K+)

Question 14

What materials are exchanged from dentine to pulp?

Answer 14

Medicaments applied to dentine
Toxins from bacteria (diffusion)
Components of filling material

Question 15

Where does the nerve enter the pulp?

Answer 15

Apical foramen

Question 16

Where are the terminal branches of the pulp nerve?

Answer 16

They enter the odontoblast layer

Some nerves enter dentinal tubules

Question 17

Where is innervation of the dentinal tubules found?

Answer 17

40% under cusps
15% in coronal dentine
4% root dentine
*few axons enter tubules, most end up in the pulp-predentine region

Question 18

What actions stimulate outward fluid flow in the hydrodynamic mechanism?

Answer 18

Cooling, drying, evaporation, hypertonic solutions, decrease in hydrostatic pressure

Question 19

What actions cause inwards fluid flow in the hydrodynamic mechanism?

Answer 19

Heating, mechanical, increased hydrostatic pressure

Question 20

How does inwards fluid flow affect pulp nerves?

Answer 20

Compresses nerve endings

Question 21

How does outwards fluid flow affect pulp nerves?

Answer 21

Stretches nerve endings which causes more pain - this is why some patients find the 3-in-1 very painful

Question 22

What is the hydrodynamic mechanism theory?

Answer 22

A stimulus acts on exposed dentine (thermal, chemical, mechanical).
This causes an increase in the rate of dentinal fluid flow.
This generates action potentials in intra-dental nerves.
AP’s pass to the brain causing pain.

Question 23

What is the Basal Layer of Weil?

Answer 23

A cell free zone in the dental pulp

Question 24

What is predentine?

Answer 24

The area between pulp and dentine where dentine is mineralised (globular dentine).
Immature, uncalcified dentine. Mainly fibrils.

Question 25

What is ground substance made up of?

Answer 25

Mucopolysaccharides
Glycosaminoglycans
Glycoproteins
Water

Question 26

What are the components of dentine?

Answer 26

Hydroxyapatite - 70% weight, 50% vol
Water - 10% weight, 20% vol
Organic matrix - 20% weight, 30% vol

Question 27

What are the types of dentinal tubules?

Answer 27

Peritubular/intratubular dentine (inside tubes)

Intertubular (between tubes)