The Dentino-Pulp Complex Flashcards
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)
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
3
Q
What’s the chemical composition of Dentine?
A
- 70% inorganic
- 20% organic
- 10% water by weight
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
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
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)
7
Q
What is the dentine between tubules called?
A
Intertubular dentine
8
Q
How do dentine tubules appear in cross-section?
A
Circular
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
10
Q
What is a benefit and drawback of Peritubular dentine?
A
+ Teeth become less sensitive
- Teeth become more brittle
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
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
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
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
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
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
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
18
Q
When are the contour lines of Owen found?
A
Mantle dentine
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
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
21
Q
What’s the Hyaline layer?
A
- Outside layer of granular layer
- Atubular and structureless
- Helps bonding of tentine to cementum
22
Q
What’s Cirumpulpal dentine?
A
- Forms the bulk of the dentine
- Uniform in structure except at the peripheries
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
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)
25
What lines are associated with the secondary curvature of dentinal tubules?
Contour lines of Owen
- Exaggerated line on the boarder of primary and secondary dentine
- Neonatal line
26
What are the dentine incremental lines?
Changes in collagen fibres orientation
- Short term = Von Ebner's lines
- Long term = Andresen lines (go across the prisms) & exaggerated neonatal line
27
What are the 2 Physiological age changes to dentine are (1)?
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
What are the 2 Physiological age changes to dentine are (2)?
Translucent dentine:
- Intratubular dentine
29
What are the 3 changes associated with dentinal responses to stimuli (1)?
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
What are the 3 changes associated with dentinal responses to stimuli (2)?
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
What are the 3 changes associated with dentinal responses to stimuli (3)?
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
Dentine Sensitivity: What's the theory behind dental sensitivity?
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
What types of stimuli can cause fluid movement within tubules?
- 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
What is dental pulp?
- 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
What's the general organisation of dental pulp?
1) Pulp chamber
2) Root (at least 1 canal)
2b) Accessory canals in the apical 3rd
36
What's the composition of dental pulp?
- Cells are in a extracellular matrix
- 75% water by weight
- 25% organic material: polysaccharides/proteins/etc
- Non-fibrous matrix
- Fibres (mainly collagen)
37
What fibres are present in dental pulp?
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
What are the components of the non-fibrous matrix?
- Glycosaminoglycans
- Proteoglycans
- Fibronectin
- Laminin
39
What's the significance of Glycosaminoglycans in the matrix?
- Bulky hydrophillic molecules that form gels
40
What's the significance of Proteoglycans?
- Core protein's surrounded by glycosaminoglycans
- Decorin: Bind collagen and TGF-beta (regulates cell proliferation/differentiation and reparative dentiogenesis) (aids dentine production)
41
What's the role of Fibronectin?
- Glycoprotein which aids cell attachment to extracellular matrix
- Widely distributed in the pulp
- Cell adhesion molecule
42
What's the role of Laminin?
- Cell adhesion molecule
- Forms part of the basement membranes and bind epithelial cells to the ECM
- Important for blood vessels
43
Whats the role of Odontoblasts in the dental pulp?
- 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
How does the single layer of Odontoblasts communicate?
- Interact via cell junctions
- Tight junctions = limit permeability and provides mechanical integrity
- Gap junctions: Allows synchronisation of cells
45
What's the role of Fibroblasts in dental pulp?
- Responsible for matrix turnover (produce collagenase/protease etc)
- Scattered all around the pulp
- Slowly produce fibres and ground substance
46
What's the role of undifferentiated cells?
- Located beneath the odontoblastic layer - capable of differentiating into Odontoblasts
- Pluripotent primitive mesenchymal cells (can differentiate into a variety of cell types)
47
Blood vessels: what's their relationship with nerves in the dental pulp?
- Close relationship
48
How do blood vessels enter the pulp?
- 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
Is there a subodontoblastic capillary plexus?
YES
- Technically, within and beneath odontoblasts
- 4-5% are fenestrated with only a basement membrane at their wall
- High fluid pressure
50
Is there a rich supply of nerve fibres within teeth?
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
What's the predominant nerve fibre within the pulp?
- 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
How do nerves enter the pulp?
- 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
Do branches from the Plexus of Raschkow enter dentinal tubules?
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
What's the function of the neuropeptide: Calcitonin gene-related peptide (CGRP)?
- 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
What are the regions of the Dental pulp?
1. Supraodontoblastic region
2. Odontoblastic layer
3. Subodontoblastic
3a: Cell free zone of Weil
3b: Cell rich zone
4. Bulk of the pulp
56
What's the Supraodontoblastic region?
- 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
What's the Cell Free Zone of Weil?
- 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
What's the Cell Rich Zone?
- Potentially an artefact layer again
- Subodontoblastic capillary and neural plexus
- Cells associated with these plei could result in the richness of this zone
59
What's the Bulk of the Pulp?
- Central area of pulp
- Loose CT
- Rich blood and nerve supply
60
What happens to the pulp as it ages?
- Size decreases
- Decrease in vascularity
- More fibrous
- Reduced innervation
- Calcification: Pulp stones or snow storm calcification
61
What are Pulp stones?
- 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
What are the clinical considerations regarding pulp?
- 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)
