pulp Flashcards
1
Q
what is pulp
A
soft connective tissue occupying the pulp space and root canals
2
Q
what does the pulp provide
A
vitality to teeth with its cells (odontoblasts, fibroblasts, undifferentiated ectomesenchymal cells, macrophages, other immunocompetent cells), fibre, vascular and nerve supply
richly vascularised + innervated tissue
3
Q
what is the apical foramen
A
opening of root pulp into the pdl near the tip of the roots
makes pulp continuous w the pdl
4
Q
why may pulp necrosis occur
A
following
1) exposure
2) contamination
5
Q
what may pulp be termed and why
A
1) coronal = in the pulp chamber in the crown of the tooth
2) radicular = extends throughout root canal spaces of roots
depending on part of tooth it occupies
6
Q
how can pulp tissue communicate with the pdl and explain these
A
lateral and accessory canals
- small communication channels between the 2
- may arise from the floor of pulp chamber or walls of the main root canal
7
Q
main function of pulp
A
producing, maintaining and repairing both primary and secondary dentine also tertiary (reactive + reparative) dentine due to injury
8
Q
what happens to the pulp in response to disease like caries
A
pulpitis
9
Q
what is the role of odontoblasts in the pulp
A
form peripheral cells
10
Q
what function of pulp mandates use of anaesthesia during cavity prep
A
protective sensory function
11
Q
how is the pulp environment sterile
A
protected from oral organisms and injury by the mineralised hard tissue walls of the coronal and root dentine (and indirectly by enamel and cementum)
12
Q
pulp morphology for every tooth is unique. what imaging techniques enable us to assess their anatomy
A
1) plain radiography (2d image)
2) cone beam computed tomography (CBCT) (3d image) = image modality used to evaluate root canal treatment
13
Q
how does pulp produce
a) primary
b) secondary
dentine
A
primary
1) Pulp tissue develops from dental papilla of tooth germ
2) peripheral cells of the papilla differentiate into odontoblasts
secondary
1) produced by odontoblasts (slowly but regularly during lifespan of tooth)
2) maintains resilient property of dentine and may help compensate for loss of coronal dentine thickness by tooth surface loss, caries or fracture
14
Q
explain the sensory function of the pulp dentine complex
A
1) detect chemical (and indirectly thermal / mechanical) stimuli
2) forms part of feedback mechanism to cns (of noxious stimuli that can be associated with tissue damage)
15
Q
what are the components of pulp
A
odontoblasts, nerve fibres and antigen presenting cells
undifferentiated stem cell role in tissue’s response to significant injury as lay down tertiary dentine at specific sites on the walls of the pulp chamber
16
Q
what is dental pulp a likely source of and why
what will increased outward flow of this help do
A
DENTINAL FLUID
bc maintains a positive interstitial tissue fluid pressure
may help dilute bacterial toxins in exposed dentinal tubules + detected by the pulp
17
Q
what does blood supply to the pulp
a) transport
b) dilute and remove
A
a) immune cells and inflammatory mediators to the area
b) damaging agents to resisting infection
18
Q
what is the process of tertiary dentine formation following a large injury or pulp exposure
A
1) stem cells from blood vessel differentiate into odontoblast like cells
2) odontoblast-like cells interact w dentine matrix components
3) reparative dentine / mineralised bridge formed
19
Q
what is the process of tertiary dentine formation following a minor injury
A
1) odontoblasts interact w dentine matrix components
2) form reactionary dentine
20
Q
what 4 distinct regions or histological ‘zones’ can be identified from coronal pulp soft tissue
A
1) SUPRA-ODONTOBLAST REGION
2) ODONTOBLAST LAYER
3) CELL-FREE ZONE (OF WEIL)
4) CELL-RICH ZONE
21
Q
describe the SUPRA-ODONTOBLAST REGION
A
1) space between most peripheral of these zones +unmineralised predentine
2) Nerve axons (most enter + terminate in dentinal tubules) AND the dendritic antigen presenting cells
3) axons on front line + positioned to detect changes in dentinal fluid movement and composition
22
Q
describe the ODONTOBLAST LAYER
A
1) most peripheral zone
2) single layer of odontoblast cells (may appear stratified)
odontoblasts reach into pre + mineralised dentine
23
Q
describe the CELL-FREE ZONE (OF WEIL)
A
1) beneath odontoblasts
2) prominent in coronal pulp
3) cant see nuclei of cells BUT cell processes of fibroblasts, odontoblasts, nerve axons + capillaries cross this area
4) capillaries, korff fibres, nerves present
4) suggestion its an artifact due to tissue shrinkage
24
Q
describe the CELL-RICH ZONE
A
1) high cell density
2) adjacent to cell-free zone in coronal pulp
3) high conc of capillaries (subodontoblastic capillary plexus) AND axons (subodontoblastic neural plexus) and fibroblast cells
4) Schwann cells + endothelial cells associated with these ‘plexi’ result in ‘cell-rich’ appearance
25
what layer is beneath the CELL-RICH ZONE
deep pulp cavity
| - contains subodontoblastic plexus of rashcow
26
what other areas of the pulp exist
1) central core = occupied by main arterioles, venules (enter by apical and accessory foramina) and nerves (enter by apical foramen)
2) bulk of dental pulp = made up of above + loose connective tissue
3) root canal = neurovascular bundle most evident
4) crown = repeated branching of nerves and blood vessels makes it less obvious
27
describe pulp composition
1) 75% water 25% organic material
2) loose connective tissue
3) cells embedded in an extracellular matrix of fibres in a ground substance
28
what is the predominant extracellular matrix component
COLLAGEN
- concentrated in most apical part of pulp
- content incs w age, fibrils organise into bundles
29
what is the non-fibrillar matrix of pulp
1) secreted by pulps cells
2) glycosaminoglycans, proteoglycans, glycoproteins, and water
3) supports cells + acts as medium for transport between cells + vasculature
30
what is the neurovascular bundle
formed by nerves together w blood vessels
31
describe the fibrous component of dental pulp
1) combo of collagen types I (60%) and III (40%) fibrils grouped into fibres thinly + irregularly scattered throughout the tissue
2) at periphery fibres more organised as aligned parallel to the forming predentine surface
32
what are GLYCOSAMINOGLYCANS (GAGS) and explain their content in mature pulp
1) unbranched polysaccharide chains mostly bound to a protein core to form proteoglycans (in pulp)
2) hydrophilic so in combo with h2o give pulp its unique gel-like properties (allow it to swell + fill most of extracellular space stabilising positions of cellular components + making movement of h2o + ions possible also reservoir for growth factors + bioactive molecules)
CONTENT
60% hyaluronic acid
20% dermatan sulphate
12% chondroitin sulphate
33
what are GLYCOPROTEINS / PROTEOGLYCANS
1) non-collagenous matrix components
2) Fibronectin (also occurs in fibrous form) and tenascin = most abundant near odontoblast layer + involved in deposition of dentine
3) Fibronectin = binds to membrane receptor proteins (integrins), mediating adhesion between cells, matrix components + vascular endothelium = maintaining structural integrity of pulp
34
what molecules can be detected at the periphery of the pulp
those more closely associated w dentine
| ie dentine sialoprotein + dentine phosphoprotein (both produced by odontoblasts)
35
list the GLYCOPROTEINS / PROTEOGLYCANS of the dental pulp and their functions
1) versican + syndecan = form large hydrated aggregates creating a gel
2) decorin = binds to type I collagen
3) biglycan = regulate collagen fibrillogenesis
4) integrins = cell surface adhesion receptors
5) fibronectin = conc near odontoblast layer + binds cells to extracellular matrix
6) tenascin = cell movement, conc near odontoblast layer
7) osteoadherin = mineralisation
36
list the cells of the dental pulp
- FIBROBLASTS
- ODONTOBLASTS
- DENTAL PULP STEM CELLS (DPSCs)
- MACROPHAGES
- T LYMPHOCYTES
- DENDRITIC CELLS
37
```
explain
a) presence
b) histological appearance
c) role
of pulp fibroblasts
```
a)
loose network throughout tissue + numerous in cell rich zone
b)
variable, reflects metabolic activity
some star shaped
some flattened and spindle shaped
c)
tissue dvlpmt = produce extracellular fibres + ground substance
ingest + degrade collagen
mature teeth = slowly produce + turnover extracellular matrix
38
```
explain
a) presence
b) histological appearance
c) role
of pulp odontoblasts
```
a)
single cell layer attached to predentine surface in mature teeth
BUT ‘pseudostratification’ = false appearance of multiple layers bc nuclei of adjacent cells in layer at different levels
b)
at crown / coronal = columnar outline
root = more cuboidal
fully differentiated are polarised columnar cells w long cell process extending into predentine + dentine in a dentinal tubule AND smaller processes linking it to adjacent odontoblasts and other pulp cells
c)
lay down secondary dentine at slow rate throughout life (at this stage odontoblast layer becomes a flatter cell layer + no of cells declines by apoptosis)
odontoblast layer provides controlled barrier between pulp + dentine
integrity of odontoblast layer and its limited permeability maintained by cell-to-cell junctions (these also link it to other pulpal cells ie fibroblasts)
39
what are the two major components of odontoblasts
1) cell bodies = lie adjacent to unmineralised dentine matrix (predentine)
2) cell processes = extend outward for variable distance through tubules in predentine + dentine
40
explain DENTAL PULP STEM CELLS (DPSCs)
1) in 2 regions = peripherally beneath odontoblast layer + centrally around blood vessels
2) multipotent so differentiate into = odontoblasts, chondrocytes, adipocytes, vascular endothelial and neurons
41
explain MACROPHAGES
1) most abundant + widely distributed defense cells in pulp
| 2) eliminate dead cells (presence of these indicates turnover of dental pulp fibroblasts occurs)
42
explain T LYMPHOCYTES
1) small numbers in normal dental pulp
| 2) numbers increase when pulp injured or subjected to toxins
43
explain DENDRITIC CELLS
1) most prominent immune cells in pulp
2) bone marrow–derived + antigen-presenting (APCs)
3) non-erupted teeth = in and around odontoblast layer
4) erupted teeth = beneath odontoblast layer + around nerves and blood vessels
5) immunosurveillance = inc in number in carious teeth (infiltrate odontoblast layer + project their processes into dentinal tubules)
6) recognise many foreign antigens + act as APCs stimulating division and activity of T lymphocytes in regional lymph nodes
44
list vessels of the pulp
- ARTERIOLES + VENULES
- SUBODONTOBLASTIC CAPILLARY PLEXUS
- LYMPTHATIC VESSELS
45
how do arterioles and venules enter pulp and what do they do once inside
- via apical foramina (+ lateral canals) as components of neurovascular bundles
- as pass up through radicular portion of pulp = give off smaller lateral branches to periphery
3) lateral branches branch into subodontoblastic area
4) no of branches given off incs as arterioles pass up through root
5) coronal region = divide + subdivide to form extensive vascular capillary network
46
explain the SUBODONTOBLASTIC CAPILLARY PLEXUS
1) capillary network in subodontoblastic area, beneath odontoblasts
2) terminal capillary loops extend to lie between odontoblasts in odontoblast layer OR between odontoblasts and predentine
- fluid in dentine = ultrafiltrate of pulpal interstitial fluid
47
explain LYMPTHATIC VESSELS
1) arise as small, blind, thin-walled vessels in coronal region of pulp
2) pass apically to exit through apical foramen
48
describe the arrangement of pulpal blood vessels
1) supply o2 + nutrients where most needed during dentinogenesis
2) 5% of capillaries in subodontoblastic zone are fenestrated = rapid movement of materials out of them
3) arteriovenous anastomoses found between peripheral pulpal vessels + allow rapid changes in blood perfusion
49
what nerves are principally contained in the nerve / neurovascular bundles in the pulp
- entering pulp = sensory afferent nerves of the trigeminal nerve (CN V)
- sympathetic efferent (motor) branches from superior cervical ganglion
- each bundle contains myelinated and unmyelinated axons
50
where do nerve fibres travel in the root
- some leave central nerve bundle @ intervals + travel to periphery
- most continue to coronal pulp + end in odontoblastic or subodontoblastic regions
51
where do nerve fibres travel in the pulp chamber
- follow course of blood vessels
- initially large nerve bundles
- spread apart peripherally as extend occlusally through pulp core
- before terminating = myelinated axons lose myelin sheath + most terminate as free unmyelinated nerve endings (in subodontoblastic plexus of Raschkow)
52
explain the subodontoblastic plexus of Raschkow
extensive plexus of nerves beneath cell-rich zone in crown
1) small no of nerves = exit + travel to and terminate around odontoblasts
2) subset of these = continue into tubules along with odontoblast processes (dont synapse w the processes BUT remain in close proximity w them for part of their length)
3) no of tubules containing nerve fibres in relation to overall no of tubules is small (incidence higher in pre than mineralised dentine)
53
what are the 2 main sensory nerve fibres, explain them
myelinated A-fibres
1) 90% narrow A-delta + 10% wider A-beta fibres
2) terminate at sub-odontoblast, odontoblast and predentine/dentinal tubules
3) responsible for rapid, sharp pain sensation associated w dentine hypersensitivity
unmyelinated C-fibres (75%)
1) terminate in pulp core or sub-odontoblast region (as free nerve endings or branches around blood vessels)
2) conduct slow, dull, throbbing pain associated w significant pulpal inflammation
3) afferent or sympathetic efferent
54
explain process of innervation of dental pulp
1) branches from alveolar nerve enter apical area
2) Multiple bundles enter pulp through apical foramen and branch further on their way to the crown
3) Most nerve axons terminate at pulp/dentine border of coronal pulp (most densely innervated area in the tissue)
4) fewer nerve endings in cervical area
5) pulp/dentine border in root pulp is sparsely innervated
6) mechanical, thermal + chemical stimuli initiate impulse that travels along pulpal axons in maxillary (V2) or mandibular (V3) of trigeminal nerve to trigeminal ganglion
55
what do trigeminal afferents do
control local environment (pulpal homeostasis + its defence mechanisms) rather than carry sensory information centrally (dentine sensitivity and pain)
56
what is the role of UNSHEATHED NERVE AXONS IN DENTINAL TUBULES (lack myelinated Schwann cell covering)
1) susceptible to changes in extracellular environment at pulp–predentine border + among odontoblast cell bodies
2) changes affect membrane properties of these nerve terminals
3) sense changes in fluid movement through dentinal tubules
4) AND changes in extracellular fluid composition (delayed in reaching core of pulp bc of barrier properties of odontoblast layer)
57
what is the role of NEUROPEPTIDES
1) activity in afferent terminals doesnt reach level of sensation
2) BUT causes release of neuropeptides (ie CGRP + substance P) by axon reflexes bc in these reflexes impulses generated in 1 terminal branch, travel centrally then, pass back down to peripheral branches
4) local control of blood flow as affect vasodilation (build-up of metabolites locally also has effect on blood flow control)
58
what is CALCITONIN-GENE-RELATED PEPTIDE (CGRP)
1) potent vasodilator
2) main agent controlling blood flow locally in periphery of dental pulp
3) role in pulpal blood flow
4) initiate / control hard-tissue production by stimulating increased production of bone morphogenetic protein-2 [(BMP)-2)
5) BMP)-2 = signalling molecule in dentine formation
59
what vascular changes occur in pulp inflammation following injury
1) mediated by local nerves (sensory and sympathetic fibres)
2) Unmyelinated autonomic C-fibres terminate in pulp core + supply arteriolar smooth muscle, act to maintain vasomotor tone so control pressure + distribution of blood in health
3) vasoactive contribution of afferent nerves largely in peripheral pulp + significant when theres inflammation
60
explain the steps in induction of neurogenic vasodilation + inflammation at the pulp/dentine border
1) external stimulus causes fluid flow (induces change in membrane properties in nerve endings at pulp/dentine border)
2) result = nerve impulse conduction along collateral endings of same axon
3) some endings are adjacent to blood vessels 4) in response to activation, terminals release sensory neuropeptides (induce vasodilation + inc permeability of vessel wall)
61
which changes to dental pulp occur with age
- REDUCTION IN VOL OF PULP CAVITY
- GRADUAL DEPOSITION OF PERITUBULAR DENTINE
- REDUCED CAPACITY FOR REPAIR FOLLOWING INJURY
- ALTERATIONS IN COMPOSITION OF THE NON-FIBRILLAR MATRI
62
explain the reduction in volume of pulp cavity
1) Secondary dentine deposition throughout life of tooth (sometimes accompanied by tertiary dentine formation) reduces size of pulp
2) pulp horns usually recede (this along w reduced innervation + addition of dentine = causes lack of sensitivity associated w older teeth)
3) root canals become thin channels + can appear almost completely calcified
63
explain the effects of gradual deposition of peritubular dentine
1) completely occludes groups of dentinal tubules producing translucent dentine
2) lead to increased brittleness + decreased permeability of dentine
64
what is - reduced capacity for repair following injury caused by
diminishing vascularity + perfusion of pulp
loss and degeneration of nerve axons
reduction in cellularity
65
explain the effects of alterations in composition of non-fibrillar matrix
1) interfere with its functions to produce…
metabolic changes
reduced cellular function
irregularities in mineral deposition
2) pulp fills with increasing amount of collagen fibres (along w reduction in stem cell no’s = impact regenerative capacity of pulp)
ie pulp capping procedures have poor outcome in elderly patients bc reduced pulpal blood supply
66
what are pulp stones
age-related change
1) pulp mineralises in this form (lamellated pulp stones consist of concentric layers of mineralised tissue)
2) discrete calcified masses w similar composition to dentine
3) singular or multiple in any tooth
4) resemble dentine in being (partially) tubular (‘true’ denticles)
5) more often resemble bone by having cells embedded within them (‘false’ denticles)
67
where do we find larger pulp stones
- attached to dentine
- orifice of pulp chamber
- in root canals
68
explain the presence of pulp stones
1) no +/or vol incs w age
2) presence signif as reduces overall no of cells in pulp
3) usually detected on radiographs (presence not an indication for active treatment)
4) can prevent access to the root canal orifices if large + attached to dentine in the pulp chamber SO these stones require removal using ultrasonic instruments prior to debridement and shaping of the root canals during endodontic treatment
69
how do we determine health status of the pulp
pulp vitality (sensibility) tests
- practical chairside test
- need vital, healthy pulp to ensure long term survival of tooth
70
when would a pulp vitality test be required
1) if tooth appearance, clinical signs or symptoms suggest compromised vitality
2) ie investigating cause for discolouration or signs of infection in mouth adjacent to specific tooth/teeth
3) indicated in planning stage prior to carrying out certain treatments which further harm compromised pulp e.g. preparing a tooth for a crown
71
what 2 tests are used to confirm vitality and explain them
temp stimulation
1) cold from cotton wool pledgets soaked in ethyl chloride
2) use to stimulate vital nerves in pulp on clean air-dried tooth
electrical stimulation
1) electric pulp test (EPT)
2) test unit passes a small current through the patient + tooth its in contact with
3) probe of electric pulp tester placed on clean dry tooth surface w a conducting gel
72
what does a vitality test suggest
1) confirm a response from a tooth
2) indication of health of pulp tissue
3) if pulp is inflamed or non- vital (partially or fully necrotic)
4) warrant further investigation
BUT
2) damage to pulp tissue causes unpleasant clinical symptoms + limits treatment options
73
what is pulp response at early stage of caries
3) pulpitis detected histologically when caries limited to enamel = painful, induces short, sharp pain (pts would seek treatment)
4) inflam is normal healing response of pulp
5) removal of caries allows inflam to subside
74
what happens to the pulp upon further caries progression / damage to dentine
1) irreversible pulpitis (pain lasting more than few secs aft a stimulus)
2) = limited chance to revert to normal if only caries removed SO also remove inflamed pulp tissue
3) irreversible pulpitis = confined to coronal pulp
4) radicular pulp = uninflamed
75
how is EXTENSIVE IRREVERSIBLE PULPITIS treated
1) complete removal of pulp tissue + endodontic treatment
2) following it pulp become necrotic, total loss of tissue functions
3) necrotic pulp tissue = becomes infected (bacteria (biofilm) + their products reach + trigger inflam reaction around root apex)
4) inflam + sepsis follow and spread to supporting tissues around tooth
76
what are the 4 adverse reactions to to caries, trauma, and iatrogenic injury (ie unintentional exposure of pulp during caries removal)
pulpitis
pulpal necrosis
periapical lesions
pain
77
what do we use when small exposure of uninfected pulp during cavity prep occurs
REGENERATION OF DENTINE BRIDGE
- repairs + forms bridge of dentine over the exposure
- odontoblast-like cells differentiate + lay down tertiary reparative dentine
78
CLINICAL CONSIDERATIONS: REGENERATION OF DENTINE BRIDGE (Reparative dentinogenesis)
what are biocompatible materials
biodentine
- facilitate (tertiary) dentine bridge formation
- place over exposure as a ‘pulp cap’ protects pulp
79
CLINICAL CONSIDERATIONS: REGENERATION OF DENTINE BRIDGE (Reparative dentinogenesis)
what are bioactive materials
Mineral Trioxide Aggregate (MTA)
- induce reparative dentinogenesis = stimulate pulpal stem cells to induce matrix formation + mineralisation
- interact w phosphate-containing fluids to form apatite precipitates
80
CLINICAL CONSIDERATIONS: REGENERATION OF DENTINE BRIDGE (Reparative dentinogenesis)
what are biologically active molecules
bone morphogenetic protein (BMP), TGF-β + other components dentine matrix
- direct, +ve effect on differentiation + activation of dentine-producing cells
- release + aid dentine bridge formation during demin of dentine w caries
NOT widely applied clinically
81
CLINICAL CONSIDERATIONS: REGENERATION OF DENTINE BRIDGE (Reparative dentinogenesis)
in what cases would bridge formation be unsuccessful
infected (carious exposure) / contaminated (fail to isolate tooth in trmnt) exposed pulp
instead remove dental pulp + replace w inert root canal filling material
82
CLINICAL CONSIDERATIONS: PULP REGENERATION TECHNIQUES
| what is root canal treatment / therapy
1) root canal anatomy complex
2) variable root canal shape
3) parts of root canal system (lateral/ accessory canals) inaccessible for mechanical debridement = prevents complete biofilm removal
4) root canal treated teeth = weakened w reduced survival rate
5) reliable outcomes
83
CLINICAL CONSIDERATIONS: PULP REGENERATION TECHNIQUES
| what is a better approach
tissue engineering to stimulate synthesis of new pulp inside empty root canal
84
CLINICAL CONSIDERATIONS: PULP REGENERATION TECHNIQUES
| what is the 1st approach to tissue engineering method
1st APPROACH
1) remove og necrotic pulp
2) prep root canal space to retain positive features of dentine surface to encourage pulp regen
3) transplanted stem cells in suitable scaffold + w morphogenetic signalling agents (ie BMPs + FGFs) introduced into prepared pulp/root canal space
85
CLINICAL CONSIDERATIONS: PULP REGENERATION TECHNIQUES
| what is the 2nd approach to tissue engineering method
1) fill root canal w
suitable scaffold
2) morphogenetic signalling agents that may chemotactically encourage stem cells from the environment of the root apex to populate the scaffold
86
CLINICAL CONSIDERATIONS: PULP REGENERATION TECHNIQUES
| what is the revascularisation technique of tissue engineering
1) stem cells from apical (SCAP) (obtained by disorganising tissue at tooth apex w endodontic file)
2) blood flow carries stem cells into empty canal space + form blood clot
3) BUT doesn't achieve regen of new pulp tissue
87
from which teeth do we commonly isolate stem cells
3RD MOLARS
- most commonly extracted + often not completed root development
- Dental pulp stem cells (DPSCs) isolated
- Root apical papilla (root foramen area) stem cells (SCAP) isolated
