1. The Dental-Pulp Complex

Question 1

what forms the dentine-pulp complex?

Answer 1

Neural crest derived ectomesenchyme

Question 2

where does the enamel form from?

Answer 2

ectoderm

Question 3

during tooth formation what is happens in the bell stage?

Answer 3

Dental papilla – leads to formation of dentine-pulp complex.

Cells of inner layer of enamel organ – differentiate into Ameloblasts
Cells of outer layer of dental papilla – differentiate into odontoblasts (makes dentine throughout life) initiating dentine deposition.

Question 4

what is the cervial loop and what does it initiate?

Answer 4

Cells of inner and outer enamel epithelium merge to form the cervical loop.

the cervical loop initiates root formation controlled by Hertwing’s epithelial sheath.

Question 5

what are the properties of dentine?

Answer 5

slide 5
1. Dentin provides the bulk and general form of the tooth.

2. Dentin forms before enamel: it determines the shape of the crown, including cusps and ridges, and the number and size of the roots.

3.Externally, dentin is covered by enamel on the anatomic crown and cementum on the anatomic root.

4.Internally, dentin forms the walls of the pulp of the pulp cavity (pulp chamber and pulp canal[s]).

Question 6

what cells for the dentine?

Answer 6

Dentin is formed by odontoblast cells of dental papilla.

As a living tissue dentin contains within its tubules the processes of the specialized cells, the odontoblasts.

Question 7

what is the composition of dentine?

Answer 7

Mineralized (hydroxyapatite) –
70% by weight

Non-mineralized –
20% organic matrix (mostly collagen- mostly Type I & minor Type V)
10% water

Question 8

does dentine contain ant growth factors?

Answer 8

yes
- Transforming growth factors (TGF)β
- Platelet-derived growth factor (PDGF),
- Matrix-metalloproteinases (MMPs).
and there are others

Question 9

what are the types off dentine

Answer 9

Primary dentine
Secondary dentine
Tertiary dentine

Question 10

what is primary dentine?

Answer 10

Primary dentine is ofrmed while the tooth is developing.

Mantle dentine
First layer of dentine

Predentine
10-40 µm layer of dentine undergoing completion of its mineralization

Question 11

what is secondary dentine?

Answer 11

deposited after root formation is complete. Pulp deposites throughout life hence why in older people their tooth cannal is narrower.

Question 12

what is tertiary dentine?

Answer 12

formed in reaction to external stimuli
Reactionary dentine
Reparative dentine

Sclerotic dentine occurs a physiological process or in response to external stimuli.

Question 13

why is the pulp reffered to as as dentine pulp complex

Answer 13

Because the odontoblast processes extend at least one-third into the dentinal tubules.

Question 14

what are the dentinal tubules?

Answer 14

1. Odontoblasts, project their cytoplasmic processes inside the dentinal tubules, up to one third of dentinal thickness.
2. Dentinal tubules are found throughout normal (physiological) dentin
3. These tubules extend from the pulp towards the periphery and joint the enamel at the DEJ in the crown.

4.They join the cementum at the dentinocementum junction at root level.

Question 15

what is predentin?

Answer 15

Predentin is 10-40 µm layer of dentine and is not mineralized rather undergoing completion of its mineralization.

This dynamic region is located between the odontoblast layer and the mineralized dentine

Question 16

how is dentine permeable and sensitive?

Answer 16

The tubular structure provides dentine with permeability and sensitivity.

Question 17

is dentine permeable in all layers?

Answer 17

The dentine permeability varies in different areas, increasing progressively towards the pulp chamber.

Question 18

what can reduce the permeabilty of dentine?

Answer 18

dentinal sclerosis educes the permeability of the dentinal tubules.

Operative procedures can create a smear layer that occludes the tubules.

Question 19

what is dentinal sclerosis

Answer 19

Sclerotic dentin is one of the form of dentin which may be a response to pathological or physiological insult in the crown & root.

the odontoblast produces dentin but block the tubules.

Question 20

what is the hydrodynamic theory’?

Answer 20

it is the main theory behind dentine sensitivity.

Question 21

Explain hydrodynamic theory?

Answer 21

The rapid displacement of the dentinal fluid within the dentinal tubules induces deformation of the odontoblastic processes.

This activates the A-δ fibres, leading to the transmission of the nociceptive signal.

Question 22

what can trigger dental fluid?

Answer 22

Many factors can trigger this dentinal fluid movement:

temperature (e.g. cold and hot substances)

osmolarity (e.g. sweet substances),

mechanical pressure (e.g. chewing and probing).

Question 23

what are the functions of the dental p

Answer 23

Formative:
-The pulp produces dentine, forming the coronal and radicular structure during the odontogenesis.

Sensitivity and proprioception:
-The pulp can sense potentially harmful stimuli (nociception).
-To a certain extent it can sense its own position (proprioception) related to pressure, thus providing a warning mechanism signalling potential tissuedamage.

Defence against infection and systemic dissemination:
-The pulp is immunocompetent and can induce scleroticand tertiary dentine formation.
-It is now known that periapical periodontitis can still develop in the presence of a vital pulp. Theinflammatory cascade elicited during the pulp defence can triggerthe cytokine cascade that leads to apical bone resorption.
-The pulpdefence prevents systemic dissemination of dental infection byinducing a foreign body reaction

Question 24

What is the Composition of Dental Pulp?

Answer 24

The pulp is a connective tissue composed of:
-different type of cells
-extracellular connective matrix (fibres and ground substance)
-blood vessels
-nerves.

Question 25

What are the Cell lineages of the dental pulp?

Answer 25

Odontoblasts
Stem cells/mesenchymal cells
Fibroblasts
Schwann cell
Defence cells (antigen presenting cells, macrophages, Lymphocytes T)

Answer 26

slide 20

The odontoblast layer is the outermost zone in the pulp, lining the predentine.

The cell free zone called the zone of Weil contains the blood capillaries and network of nerve fibers.

The cell rich zone is formed of fibroblasts, undifferentiated stem cells and immune cells.

The pulp proper is the central mass of the pulp tissue and contains the larger blood vessels, nerves, fibroblasts and other cells.

Question 27

what are odontoblasts

Answer 27

Odontoblasts are tall and columnar in the crown and in the root they are cuboidal.

They last throughout life and produce dentine matrix.

Organized in single layer of cells (odontoblastic layer) facing the predentine.

localized below the cytoplasmic projection (odontoblastic process), which is contained within the dentinal tubules.

The odontoblast is polarized: the nuclei are localized towards the pulp; a mitochondria-rich area is closer to the predentine

Question 28

what are the fibroblasts?

Answer 28

The fibroblasts are the most abundant cell lineage.

The fibroblast produces the extracellular matrix (glycosaminoglycan, proteoglycans, and glycoprotein), representing the medium for the diffusion of signals and nutritive substance.

Collagen types I and III are the most diffuse type of fibres.

Question 29

what is a milton solution?

Answer 29

(1% Sodium Hypochlorite) is required to dissolve infected fibrous tissue.

effective irrigant used in root canal treatment and dissolves the necrotic pulp tissue.

Question 30

what are the The vessels of the dental pulp?

Answer 30

Arterioles
Capillaries
Venules
Arteriovenous shunts
Lymph vessels

Capillaries more abundant in the odontoblastic layer where they are more needed to support with nutrients the dentinogenesis

Question 31

what are the nerves of the dental pulp?

Answer 31

Mandibular and maxillary branches of the trigeminal nerve main nerve that supplies the teeth.

80% of the nerve fibres are unmyelinated C fibres and 20% consist of myelinated A fibres.

Question 32

what is the Rashkow’s nervous plexus?

Answer 32

The nerves are in close proximity with the blood vessels. The nerve fibres create a rich network.

Question 33

what are the a fibres?

Answer 33

there is two types and they are myeliniated
A-β - very fast conduction speed (30–37 m/sec).
A-δ - fast conduction (6–30 m/ sec).

The A fibres induce the sharp, short pain associated with dentinal hypersensitivity.

After leaving the Rashkow’s nervous plexus the A fibres lose their outer Schwann cells layer and enter the dentinal tubules for the first 100 μm, in close conjunction with the odontoblastic processes.

Question 34

what are the c fibres?

Answer 34

Unmyelinated fibers:

slower conduction speed of the signal, being unmyelinated.
The nociceptive signal conducted by these fibres is typically of a dull non-localized pain associated with the advanced stages of irreversible pulpitis.

Question 35

what are the Lateral and accessory canals?

Answer 35

1. size ranges between 20 and 200 mm
2. are very frequent in the furcation of molars
3. are formed during dentinogenesis
4. may allow the passage of bacteria
5. sustain endo-perio lesions

Question 36

what is the Dentine pulp response to caries?

Answer 36

Reduction in dentine permeability

The tertiary dentine self-defence mechanism - Tertiary dentine is formed to further protect the pulp from an on-going potential bacterial infection.

Pulp immunity

Question 37

explain the Reduction in dentine permeability in regards to Dentine pulp exposed to caries.

Answer 37

Dentine sclerosis reduces permeability and it is localized underneath carious lesions.

Rapid insults there is no host response and adaptation of the pulp, the dentinal sclerosis process is interrupted and the odontoblast process coagulates within the tubules forming the dead tracts.

Pulp stones may also form in the presence caries.

Question 38

explain the tertiary dentine self-defence mechanism in regards to Dentine pulp exposed to caries.

Answer 38

Reparative dentine deposition occurs when an excessive damage occurs to the odontoblastic layer.
Newly recruited dental pulpal stem cells are recruited and differentiate in odontoblast-like cells.
Dentinal tubules are usually not present or not continuous with those from secondary or reactionary dentine.

Reactionary dentine
formed when the insult to the odontoblast is not sever and the odontoblastic layer survives: the dentinal tubules structure is conserved. The deposition speed is increased. Morphologically tertiary reactionary dentine is similar to the primary and secondary dentine.

look at slide 44

Question 39

why can the pulp completely minerlise?

Answer 39

This is a consequence of traumatic injury that is insufficient to kill the pulp

Question 40

explain pulp immunity.

Answer 40

pulp - immunocompetent connective tissue - respond to the bacteria by activating host immune response.

inflammatory process -triggered at the early stages of caries once the enamel or cementum is breached.

The passage of bacterial by-products through dentinal tubules before dentinal infection occurs.

The decay process - release of enzymes and other proteases within the collage matrix of the dentine.

passage of bacterial by-products in the dentinal tubules can trigger the odontoblasts to release cytokines.

The A-fibres associated with odontoblastic processes trigger a nociceptive signal, which feeds back to the autonomous system, increasing pulpal blood flow; increase the dentinal fluid extravasation.

defence cells are recruited (e.g. dendritic cells, polymorph nucleates, and macro-phages).

Pulp innervation plays an important role in the regulation of blood flow. Vasodilation is triggered to improve the clearance of bacterial by-products and increase the immune response.

Question 41

what is the pulp like in elderly patients?

Answer 41

-Has decreased in size
-Is more fibrous
-Remains functional
-Can respond to stimuli
-Can form dentine

Question 42

what is Atresic pulp?

Answer 42

complete mineralisation of the pulp.

if there is Partial mineralisation – Pulp stones/sclerosed canal

Question 43

what are the Routes of Pulpal inflammation?

Answer 43

-Dental caries (bacteria )Dental trauma >cracks, fractures> bacteria
-Cavity preparation
-Dental materials
-Bacterial leakage at the interface between tooth and restorations
-Exposure of dentine > bacteria

Question 44

what are the signs of pluptis

Answer 44

Redness
Swelling
Temperature
Pain
Loss of function

Question 45

How to diagnose the pulpal status?

Answer 45

-history
-clinical examination
-special tests (vitality test)
-radiological examination

Question 46

explain a thermal test.

Answer 46

Thermal tests: hot GP, Endo frost

Normal response is the sensation felt to hot or cold and disappears following removal of stimulus

Abnormal response is lack of response, lingering or intensification of a painful sensation after removal of stimulus or an immediate excruciating painful sensation.

Test a few of the surrounding teeth to see how the patient would normally react.

Question 47

what is the electric pulp tester?

Answer 47

Electric Pulp tester:

vitality is assessed by intactness and health of vascular supply and not the status of pulpal nerve fibres.

A response to EPT denotes that some viable nerve fibres are present in the pulp and are capable of responding.
Tooth needs to be dried and isolated, should use a control tooth to form a baseline response.

Question 48

what is the treatment for irreversible pulpitis?

Answer 48

Vital pulp therapy (removing the inflamed part of the pulp, maintaining the pulp vitality)

Root canal treatment ()

Question 49

Summary: What is the purpose of the dental pulp?

Answer 49

Forms dentine
Forms the root
Repairs dentine
Defence against infection
Prevents infection entering jaw bone.