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Oral Biology > The Dentino-Pulp Complex > Flashcards

The Dentino-Pulp Complex Flashcards

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1
Q

What are the physical properties of Dentine?

A
  • Fresh dentine is pale yellow
  • Harder than bone and cementum
  • Softer than enamel
  • Tubular nature renders it strong (high compressive, tensile and flexural strength)
  • Permeable, depending on the patency of the tubules (decreases with ageing)
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2
Q

What are the key features of Dentine?

A
  • Forms the bulk of the teeth
  • Large number of parallel tubules in a mineralised collagen matrix
  • Tubules contain the processes of odontoblasts
  • Formed constantly throughout life
  • Sensitive tissue
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3
Q

What’s the chemical composition of Dentine?

A
  • 70% inorganic
  • 20% organic
  • 10% water by weight
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4
Q

What’s the inorganic composition of Dentine?

A
  • Calcium hydroxyapatite crystals (smaller than enamel crystals)
  • Calcium poor and carbonate rich (bad for erosion)
  • Crystals are found between and on the collagen fibrils
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5
Q

Whats’s the organic composition of Dentine?

A
  • 90% collagen (mainly type I)
  • Dentine phospho-proteins

(Phosphorphoryn - most acidic protein known - can bind to calcium - aids mineralisation of dentine)

  • Proteoglycans
    (Biglycan & decorin - important role in collagen assembly, cell adhesion. migration, differentiation and proliferation)
  • More like a modified CT
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6
Q

Dentine Tubules: How far do the tubules extend?

A

Extend from the pulp surface to the amelo-dentinal & cemento-dential junctions

  • Have a curved sigmoid path (primary and secondary)
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7
Q

What is the dentine between tubules called?

A

Intertubular dentine

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8
Q

How do dentine tubules appear in cross-section?

A

Circular

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9
Q

How do dentine tubules change over time?

A
  • Walls of newly formed tubules at the pulp surface are made of mineralised type I collagen
  • Maturation of tubules is associated with deposition of another type of collagen
  • Followed by reduction in size of lumen or complete obliteration = PERITUBULAR OR INTRATUBULAR DENTINE
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10
Q

What is a benefit and drawback of Peritubular dentine?

A

+ Teeth become less sensitive

  • Teeth become more brittle
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11
Q

What are the characteristics of Peritubular dentine?

A
  • Lacks collagen matrix
  • Increased radiographic and electron density (more mineralised)
  • Main protein isn’t phosphophoryn
  • Inorganic component is mainly carbonated apatite with different crystal structure
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12
Q

What’s the content of Dentinal tubules?

A

1) Odontoblastic processes
2) Afferent nerve terminals
3) Antigen presenting cells processes
4) Extracellular dentinal fluid

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13
Q

What are Odontoblastic processes?

A
  • Extensions of the Odontoblasts (produce dentine) which are found in the pulp
  • Odontoblastic process branches which extend into the enamel = Enamel spindles
  • Contain organelles - predominantly at the perdentine area
  • In the inner layers of the dentine; the processes occupy almost the full width
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14
Q

Dentinal Tubules: What are Afferent nerve terminals and what are they associated with?

A
  • Sensory nerve fibres of the dental pulp; afferent endings of the trigeminal cranial nerve
  • Mainly present in the inner layers of dentine
  • Intimate relationship with odontoblastic processes
  • Related to tooth sensitivity & mostly un-myelinated
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15
Q

Dentine tubules: What’s the purpose of Antigen presenting cells processes?

A
  • Immune response to infection
  • Appear as small processes in the tubules near the pulp
  • Within and beneath odontoblasts
  • Limited to pre-dentine area and below
  • In carious dentine (bacterial) they extender deeper in the tubules
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16
Q

Dentine tubules: Whats Extracellular dentinal fluid?

A
  • Unknown composition: Know it has higher potassium and lower sodium ion levels that other fluids
  • Positive force from pulpal tissure pressure
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17
Q

What’s Mantle dentine?

A
  • Most peripheral (1st to be formed) layer of dentine (outermost layer next to enamel)
  • 20-150μm in width
  • Different orientation of collagen fibres (perpendicular)
  • Less mineralised then circumpulpal dentine
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18
Q

When are the contour lines of Owen found?

A

Mantle dentine

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19
Q

What’s interglobular dentine?

A
  • Minerals deposited as globules (calcospheres) which fuse to form a uniform calcified tissue
  • Hypomineralised
  • Found beneath mantle detine
  • Uncalcified interglobular area appear DARK
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20
Q

What’s the granular layer of Tome?

A
  • Peripheral root dentine has a dark granular zone
  • Dentinal tubules branch and loop back on themselves which creates air spaces
  • “tree top” appearance of tubules
  • Hypomineralised granular layer
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21
Q

What’s the Hyaline layer?

A
  • Outside layer of granular layer
  • Atubular and structureless
  • Helps bonding of tentine to cementum
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22
Q

What’s Cirumpulpal dentine?

A
  • Forms the bulk of the dentine

- Uniform in structure except at the peripheries

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23
Q

What’s Predentine?

A
  • Initially laid dentine matrix prior to mineralisation
  • Mineralisation front may show a globular or a linear appearance
  • 10-40μm in width & thicker in young teeth
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24
Q

What lines are associated with the primary curvatures of dentinal tubules?

A

Schreger lines - follow a sinusoidal path called the primary curvature (S-shape)

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25
Q

What lines are associated with the secondary curvature of dentinal tubules?

A

Contour lines of Owen

  • Exaggerated line on the boarder of primary and secondary dentine
  • Neonatal line
26
Q

What are the dentine incremental lines?

A

Changes in collagen fibres orientation

  • Short term = Von Ebner’s lines
  • Long term = Andresen lines (go across the prisms) & exaggerated neonatal line
27
Q

What are the 2 Physiological age changes to dentine are (1)?

A

Secondary dentine:

  • Normal change in dentine (just change in tubular direction)
  • Nearer the pulp as it forms later
  • Forms once the root is completed and the tooth comes into occlusion
  • Similar to primary dentine
  • Sudden change in tubules direction
  • Slower deposition thus less regular
  • Closer incremental lines
28
Q

What are the 2 Physiological age changes to dentine are (2)?

A

Translucent dentine:

  • Intratubular dentine
29
Q

What are the 3 changes associated with dentinal responses to stimuli (1)?

A

Tertiary dentine:

  • External stimuli can induce the pulp to produce more calcified material
  • NOT A CONTINUATION OF PRIMARY AND SECONDARY DENTINE
  • Cells in the pulp differentiate into odontoblasts (produce dentine) – production of type I collagen and dintine sialoprotein
30
Q

What are the 3 changes associated with dentinal responses to stimuli (2)?

A

Sclerotic dentine:

  • Stimuli induces the deposition of material inside the dentine tubules
  • Similar appearance to transparent dentine but it has a different composition to intratubular dentine
  • Spindles are observable - appear as continuations of the dentine
31
Q

What are the 3 changes associated with dentinal responses to stimuli (3)?

A

Dead Tracts of Fish:

  • Primary odontoblasts which have been kidded by external stimuli and results in empty tubules
  • Might be sealed at their pulpal end by tertiary dentine
  • Air filled
  • Caused by cavity and acid-wear
32
Q

Dentine Sensitivity: What’s the theory behind dental sensitivity?

A

Hydrodynamic theory (Fluid movement within the tubules):

  • Stimuli applied to dentine causes fluid movement; can be sufficient to depolarise the nerve endings and cause them to fire
    • In the tubules
    • at the dentine-pulp junction
    • in the plexus of Raschkow (innovate the odontoblastic layer in pulp)
33
Q

What types of stimuli can cause fluid movement within tubules?

A
  • Heat
  • Osmotic pressure
    Drying
  • Cold stimuli causes inward movement of fluids
  • Inward/outwards movement mechanically affect nerve terminals
  • Tubular branching near DEJ explain the higher sensitivity
  • A- group fibres – responsible for the sensitivity of dentine and thus for the mediation of the sharp induced by dentine sensitivity
34
Q

What is dental pulp?

A
  • Innermost part of the tooth
  • Unmineralised tissue
  • Composed of 2 parts: Pulp chamber and root canals
  • Highly innervated tissue with no space for movement
35
Q

What’s the general organisation of dental pulp?

A

1) Pulp chamber
2) Root (at least 1 canal)
2b) Accessory canals in the apical 3rd

36
Q

What’s the composition of dental pulp?

A
  • Cells are in a extracellular matrix
  • 75% water by weight
  • 25% organic material: polysaccharides/proteins/etc
  • Non-fibrous matrix
  • Fibres (mainly collagen)
37
Q

What fibres are present in dental pulp?

A

Collagen type I

  • Fibrils thinly scattered through the pulp
  • Randomly organised
  • At peripheries - parallel to the predentine surface
  • Right angles to the amelo-dentine junction in mantle dentine (Von Korff’s)
  • More crosslinking with age

Collagen type III

  • Present in large amounts (41% pulpal collagen)
  • Only alpha1 chains
  • Collagen type V + VI present in small amounts
38
Q

What are the components of the non-fibrous matrix?

A
  • Glycosaminoglycans
  • Proteoglycans
  • Fibronectin
  • Laminin
39
Q

What’s the significance of Glycosaminoglycans in the matrix?

A
  • Bulky hydrophillic molecules that form gels
40
Q

What’s the significance of Proteoglycans?

A
  • Core protein’s surrounded by glycosaminoglycans
  • Decorin: Bind collagen and TGF-beta (regulates cell proliferation/differentiation and reparative dentiogenesis) (aids dentine production)
41
Q

What’s the role of Fibronectin?

A
  • Glycoprotein which aids cell attachment to extracellular matrix
  • Widely distributed in the pulp
  • Cell adhesion molecule
42
Q

What’s the role of Laminin?

A
  • Cell adhesion molecule
  • Forms part of the basement membranes and bind epithelial cells to the ECM
  • Important for blood vessels
43
Q

Whats the role of Odontoblasts in the dental pulp?

A
  • Produce Dentine
  • Found at the periphery in dental pulp
  • Form a layer of single cells attached to the predentine by a single process
  • Coronal odontoblasts are columnar in the outline BUT cuboidal in the root
44
Q

How does the single layer of Odontoblasts communicate?

A
  • Interact via cell junctions
  • Tight junctions = limit permeability and provides mechanical integrity
  • Gap junctions: Allows synchronisation of cells
45
Q

What’s the role of Fibroblasts in dental pulp?

A
  • Responsible for matrix turnover (produce collagenase/protease etc)
  • Scattered all around the pulp
  • Slowly produce fibres and ground substance
46
Q

What’s the role of undifferentiated cells?

A
  • Located beneath the odontoblastic layer - capable of differentiating into Odontoblasts
  • Pluripotent primitive mesenchymal cells (can differentiate into a variety of cell types)
47
Q

Blood vessels: what’s their relationship with nerves in the dental pulp?

A
  • Close relationship
48
Q

How do blood vessels enter the pulp?

A
  • Arterioles and venules enter via the apical foramen and lateral canals
  • Once in the canal they branch to the peripheries and branch profusely in the coronal pulp chamber
49
Q

Is there a subodontoblastic capillary plexus?

A

YES

  • Technically, within and beneath odontoblasts
  • 4-5% are fenestrated with only a basement membrane at their wall
  • High fluid pressure
50
Q

Is there a rich supply of nerve fibres within teeth?

A

YES

  • 2500 axons enter a mature premolar
  • 25% are myelinated afferents
  • 90% are Alpha fibres - these are associated with acute pain and with sensations of temperature pressure
51
Q

What’s the predominant nerve fibre within the pulp?

A
  • Unmyelinated C fibres
  • Afferent or autonomic (sympathetic fibres associated with blood vessels)
  • C fibres have a slow conduction velocity and are associated with chronic or dull pain + with sensations of warmth/mechanical/chemical stimuli
  • Most fibres are nociceptors
52
Q

How do nerves enter the pulp?

A
  • Part of neuro-vascular bundle
  • Branch into coronal part of pulp
  • Branches end in and around odontoblastic layer : plexus of nerves beneath the odontoblasts= PLEXUS OF RASCHKOW
53
Q

Do branches from the Plexus of Raschkow enter dentinal tubules?

A

YES

  • Lots of axons are present in the tubules and the peripheries of dentine - devioid of Schwann cells
  • Lack of Schwann cells facilitates their response to stimuli from the immediate environment
54
Q

What’s the function of the neuropeptide: Calcitonin gene-related peptide (CGRP)?

A
  • CGRP is a potent vasodilator which controls pulpal blood flow
  • Synthesised by neurons and transported by axons
  • May contribute to the control of hard tissue formation
  • Function of nerves in the pulp is maintaining the local environment
55
Q

What are the regions of the Dental pulp?

A
  1. Supraodontoblastic region
  2. Odontoblastic layer
  3. Subodontoblastic
    3a: Cell free zone of Weil
    3b: Cell rich zone
  4. Bulk of the pulp
56
Q

What’s the Supraodontoblastic region?

A
  • Between the odontoblastic cell bodies and the predentine
  • Unsheathed axons are present (predentinal plexus of Bradlaw)
  • Dendritic antigen presenting cells present
  • 1st region in the pulp where changes in the tubules could be detected
57
Q

What’s the Cell Free Zone of Weil?

A
  • Cell free zone/Anuclear zone
  • Cell processes of fibroblasts, odontoblasts, axons and capillaries are found across this region
  • Only in the coronal pulp of erupted teeth
  • Might be considered an artefact
58
Q

What’s the Cell Rich Zone?

A
  • Potentially an artefact layer again
  • Subodontoblastic capillary and neural plexus
  • Cells associated with these plei could result in the richness of this zone
59
Q

What’s the Bulk of the Pulp?

A
  • Central area of pulp
  • Loose CT
  • Rich blood and nerve supply
60
Q

What happens to the pulp as it ages?

A
  • Size decreases
  • Decrease in vascularity
  • More fibrous
  • Reduced innervation
  • Calcification: Pulp stones or snow storm calcification
61
Q

What are Pulp stones?

A
  • Either single or in a group
  • Either true or false denticles:
    + T = resemble dentine (tubular)
    + F = resemble bone (trapped cells)
  • Some are attached to dentine
  • Case complications when carrying out root canal therapy
62
Q

What are the clinical considerations regarding pulp?

A
  • Defects in dental tissue are mediated through the pulp
  • Sense organ of the tooth so it requires anaesthesia
  • Possess defence mechanisms against caries and trauma (stimulating tertiary dentine)

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