The Dentino-Pulpal Complex

Question 1

Dentine - basic overview?

Answer 1

Overview:

• forms the bulk of the tooth
• large number of parallel tubules in a generalised collagen matrix
• tubules contain the processes of odontoblasts
• sensitive
• formed throughout life

Question 2

Dentine - physical properties?

Answer 2

Physical properties:

• fresh dentine is pale yellow
• harder than the (_______) cementum
• softer than the enamel
• permeable, depending on the latency of the tubules

Question 3

Dentine - chemical composition - inorganic and organic overview?

Answer 3

• Dentine is 70% inorganic, 20% organic and 10% water
  Inorganic composition:
• calcium hydroxyapatite; are Ca poor and carbonate rich
• much smaller than enamel hydroxyapatite
• found in and between collagen fibrils
  Organic composition:
• Col I forms 90%
• DPP and proteoglycans also present
  Hexagonal shaped crystals

Question 4

Dentine - chemical composition - organic matrix? composition? Phospphoryn? Proteoglycans and role? Other present proteins? GF? Lilies?

Answer 4

Organic matrix:
- 90% of organic matrix (Col I)
- phosphophoryn (PP-H); main phosphoprotein (most acidic) and high calcium binding properties (implicated in mineralisation)
- main proteoglycans in dentine are bigkycan and decorin
- proteogly role in collagen assembly, cell adhesion, migration, differentiation and proliferation (role in mineralisation)
- GAGs also present
- y-carboxyglutamate-containing proteins in dentine
- bind strongly to hydroxyapatite crystals (role in mineralisation)
- acidic proteins; osteonectin, osteopontin present
- GF: IGF and TGF
Lipids:
- 2%
- phospholipids involved in formation and growth of apaptite crystals

Question 5

Dentine tubules - location? Shape? Presentation? Xsec? Between tubules? Size changes and why? Secondary curvature? Branching?

Answer 5

Location:
- extend from the pulp surface to the amelo-dentinal and the cementi-dentinal junctions 
Shape:
- curved sigmoid course 
Presentation:
- form primary curvature of dentine 
Xsec:
- circular
Between tubules:
- intertubular dentine
Size changes:
- 2.5um at pulpal end and 1um at enamel end
Why:
- odontobalsts retreat inwards, occupy a smaller area, and so the tubules become closer together 
Secondary curvatures:
- coincidenwith adjacent tubules gove risento contour lines of Owen
Branching:
- branch near the enamel-dentine junction
- in root, terminal branches loop
- more obvious in predentine

Question 6

Dentine tubules - intratubular dentine - characteristics? Formation?

Answer 6

Formation:

• walls of newly formed dentinal tubules at the pulp surface are made of Col I
• maturation of tubules assoc with deposition of another type of dentine in walls
• reduction in lumen (can be complete obliterated)
• called intratubular dentine

Question 7

Intratubular dentine - characteristics? Differences to inter?

Answer 7

• lacks collagen matrix

- increased radiographic and electron density (15% more mineralised)

Question 8

Intratubular dentine - inorganic component? physiological ageing?

Answer 8

Inorganic component:
- carbonated appetite with a different crystalline form
- hypocalcified areas
Physiological ageing:
- leads to complete obliteration of tubules with intratubular dentine (root dentine)
- appear translucent in water (butterfly Xsec, due to convergence of of tubules)

Question 9

Contents of the dentinal tubules - odontoblastic processes - structure differences? Organelles? Location?

Answer 9

Structure differences:
- variable structure at various levels
Organelles:
- more in predentine area
- presence of microtubules and intermediate filaments
Location:
- inner layers of dentine, the processes occur the full width (remnants of processes seen in the peripheral parts of the tubules (after it has degenerated)
- degeneration of peripheral end (theory for withdrawal of odontoblasts

Question 10

Contents of the dentinal tubules - afferent nerve terminals - location? Relationship? Organelles?

Answer 10

Location:
- inner layers of dentine
Relationship:
- with the odontoblastic proces
Organelles:
- mito and vesicles

Question 11

Contents of the dentinal tubules - sensory terminals - location? Size? Organelles?

Answer 11

Location:
- coronal dentine beneath cusos (in 80% of tubules)
- sparse in cervical and root dentine
Size: 
- narrower than odontoblastic processes 
Organelles:
- microtubles and microfilaments

Question 12

Contents of the dentinal tubules - antigen presenting cell processes - appearance? Role? Location?

Answer 12

Apperance:
- small processes in the tubules near pulp
Role:
- immunocompetent APC
Location:
- within and beneath odontoblasts 
- processes limited to predentine
- extends deeper in tubules under caries

Question 13

Contents of the dentinal tubules - extracellular dentinal fluid - brief composition? Role? Pa?

Answer 13

Composition:
- higher K and lower Na in comparison
Role:
- this balance affects the membrane properties of cells
Pa:
- positive force from the pulpal tissue pressure

Question 14

Mantle dentine - formation order? Size? Differences from circumpulpal dentine?

Answer 14

Order:
- most peripheral layer of dentine (1st)
Size:
- 20-150um
Differences:
- 5% less mineralised
- Col fibres perpendicular in the amelo-dentinal junction 
- branching of tubules 
- different mineralisation process

Question 15

Interglobular dentine - shape? Fusion? Location?

Answer 15

Shape:
- minerals deposited as globular (calcospheres)
Fusion:
- form a uniform calcified tissue
Location:
- beneath mantle dentine (incomplete fusion)
- undercalcified interglobular areas appear dark
- tubules pass areas

Question 16

Granular layer of Tome - what is it? direction? Role? Apperance?

Answer 16

What is it:
- peripheral root dentine had a dark granular layer
Direction:
- dentinal tubules branch and loop back on themselves
Role:
- create air spaces
Apperance:
- tree top appreance of tubules
- hypimineralised granular layer
- incomplete fusion of calcospherites

Question 17

Dentino-pulpal complex - Hyaline layer - located? Width? Structure basic? Helps with?

Answer 17

Location:
- outaidenthe granular layer 
Width:
- 20um
Structure:
- atubular and structureless
Helps:
- in binding dentine to cementum

Question 18

Dentino-pulpapl complex - Circumpulpal dentine - main? Structure basic?

Answer 18

Main:
- bulk of the dentine
Stricture:
- uniform except at peripheries

Question 19

Dentino-pulpapl complex - predentine - when laid down? Structure during mineral? Width?

Answer 19

Laid down:
- prior to mineralisation 
Structure during mineralisation:
- show a.globular or linear apperance 
Width:
- 10-40um
Thicker in younger teeth

Question 20

Dentino-pulpapl complex - structural lines in dentine? Primary curvature? Secondary curvature? Incremental lines?

Answer 20

Primary: curvatures of dentinal tubules;
- Schreger lines
Secondary: curvatures of dentinal tubules;
- contour of lines of Owen
Incremental lines:
- von Ebner's lines 
- Andresen lines

Question 21

Dentino-pulpapl complex - primary curvature lines (Schreger lines)? Section cut? Difficulty?

Answer 21

Section cut:
- longitudinally
Difficulty:
- to see in cross sections

Question 22

Dentino-pulpapl complex - secondary curvature lines (contour lines of Owen)? Location?

Answer 22

Location:

• exaggerated line on the border of primary and secondary dentine
• neonatal line

Question 23

Dentino-pulpapl complex - Von Ebner’s lines - location and size?

Answer 23

Von Ebner’s Lines:

• cusp dentine: 4um separate every 2 lines
• root dentine: 2um separate every 2 lines

Question 24

Dentino-pulpapl complex - Andresen Lines - size apart? lines found in-between?

Answer 24

Size:
- 16-20um apart
Lines found inbetween:
- 6-10 lines of Owen between every 2 Andresen lines
Exaggerated neonatal line

Question 25

Dentino-pulpapl complex - physiological age changes? changes associated with dentinal responses to stimuli?

Answer 25

``` Physiological changes: - secondary and translucent dentine Changes associated to dentinal responses to stimuli: - tertiary and sclerotic dentine - dead tracts of Fish ```

Question 26

Dentino-pulpapl complex - | Secondary dentine - start formation? similar structure? differences to primary?

Answer 26

``` Start formation: - form once the root is completed and the tooth comes into occlusion Similar structure: - to primary dentine Differences: - sudden change in tubule direction - slower deposition thus less regular - closer incremental lines Close to pulp ```

Question 27

Dentino-pulpapl complex - Translucent dentine - how it occurs? location?

Answer 27

How it occurs: - obliteration of tubules with intratubular dentine Location: - root dentine

Question 28

Dentino-pulpapl complex - Tertiary dentine - stimuli? types of dentine formed? variable appearance? differentiation? production of? interactions? Factors released (induces)

Answer 28

``` Stimulus: - external (trauma) induce the pulp to produce more calcified material Dentine formed: - irregular secondary dentine, reparative dentine, reactionary dentine, response dentine and osteodentin Variable appearance: - tubular, irregular and atubular Differentiation: - pulp cells into odontoblasts - or original odontoblasts Production of: - Col I and dentine sialoprotein Interactions: - epith-mesenchymal interactions Factors released during inflammation? ```

Question 29

Dentino-pulpapl complex - Sclerotic dentine - stimuli? similar structure? different composition? composition? exposed tubules?

Answer 29

``` Stimuli: - induce the deposition of material inside the tubules (forming sclerotic dentine) Similar structure: - to transparent dentine Diff composition: - from intratubular dentine Composition: - apatite crystals and octacalcium phosphate crystals Exposed tubules: - might contain components from saliva ```

Question 30

Dentino-pulpapl complex - Dead Tracts of Fish - formed by? Sealed? defintion?

Answer 30

Formed by: - primary odontoblasts killed (external stimuli) - could retreat before form of intratubular dentine (forming empty tubules) Sealed: - at their pulpal end by tertiary dentine - air filled, thus light will be internally reflected and they will appear dark Definition: - is the term given to these air filled tubules

Question 31

Dentino-pulpapl complex - Dentine sensitivity - different stimuli? food related stimuli? sensitivity due to? hydrodynamic theory? outward/inward movement stimuli?

Answer 31

Different stimuli: - cold air/water - mechanical contact (bur, probe) - dehydration (cotton, air) - heat produced during drilling - chemicals Food related: - thermal changes - osmotic changes sensitivity due to: - nerve endings in the dentine - odontoblastic process - movement of fluid within dentinal tubules Hydrodynamic theory: - stimuli applied to dentine cause fluid movement - sufficient to depolarise nerve endings (in tubules, dentine-pulp junction and in plexus of Raschkow) - stimuli cause outward movement of fluids (heat, osmotic pressure and drying) - cold stimuli causes inward movement of fluids - both movements affect nerve terminals - tubular branching near DEJ explain higher sensitivity - removing intracellular fluid disables a fibres

Question 32

Dentino-pulpapl complex - Dental pulp - general organisation (contained, continuous, what is it, composition basic), composition of pulp? Pulp fibres? Fibre formation?

Answer 32

General organisation: - pulp contained within the pulp chambers and root canals - apically, the pulp becomes continuous with the PDL - specialised CT - odontoblasts lie on peripheries, nerve terminals, APCs and BVs - each root has one canal - accessory canals apical third Composition of pulp: - cells in ECM - 75% water and 25% organic - fibres and non-fibrous matrix - Col main component Pulp fibres: - Col I; fibrils thinly and randomly scattered, at the peripheries, parallel to predentine and right angles to the amelodentinal junction in mantle dentine (von Korff's) - Col III; in large amount, random scatter, only a1 chains and 41% pulpal collagen - V and VI and fibrillin Fibre formation: - alpha chain (3) - form procollagen (procollagen peptidase) - collagen molecule - assembles collagen fibril - assembles fiber

Question 33

Dentino-pulpapl complex - pulp - nonfibrous matrix - GAGs (definition and types)? Proteoglycan (definition and types)? and adhesion molecules?

Answer 33

Non-fibrous matrix: - GAGs; polysaccharide chain, bulku hydrophilic molecules from gel (chondroitin sulphate predominates also dermatan and heparan, also hyaluronan) Proteoglycans: core protein surrounded by GAGs - decorin (bind Col and TGFb) - biglycan (reg Col fibrinogen) - versican (proteogly aggreg) - syndecan (attach to Col) - Tensascin (cell adh) Adhesion molecules: integrin - fibronectin (cell attach to ECM, and cytoskel, reg cell shape, mig and diff) - laminin (base mem and binds epith to ECM, bind sig mole, odontoblastic bodies and processes coated with laminin)

Question 34

Dentino-pulpal complex - Dental pulp - odontoblasts (description of cell, location, shapes in diff sections and cell junctions)

Answer 34

Odontoblasts: - fully differentiated, polarised columnar cell with a long process inside a tubule - cell body (50umx5-10um) - small processes link adj odontoblasts and other pulp cells - form a layer of single cells attached to the predentine (by single process) - coronal odonto are columnar in outline, cuboidal in root - oblique section (appear pseudostratified) Cell junctions: - desmosomes, tight junctions and gap junctions

Question 35

Dentino-pulpal complex - dental pulp - fibroblasts (location, production and degrad)

Answer 35

FIbroblasts: - scattered in pulp - slowly produce fibres and GS - pulp fibroblasts degrade ECM - matrix turnover - can produce hard tissue - prod of GFs and cytok - apoptosis

Question 36

Dentino-pulpal complex - dental pulp - immune cells - (T-lympho, macro and APC)

Answer 36

``` T-lympho: - small numbers increases during injury Macrophages: - diff morpho in rest form - widely distributed and large numbers - denser around BVs and odontoblast APCs: - 3 or more branching processes - numerous around BVs and odonto - induce lympho prolif and mig to lymph nodes ```

Question 37

Dentino-pulpal complex - dental pulp - undifferentiated cells (location and name?

Answer 37

- beneath the odontoblastic layer capable of diff into odonto - pluripotent primitive mesenchymal cells could diff into cell variety

Question 38

Dentino-pulpal complex - dental pulp - BVs (relation, enter, course, branching, location, anastomoses, vasoconstrictor, blood flow)?

Answer 38

Relation: - with nerves Enter: arterioles and venules - via the apical foramen and lateral canals Course: - run inside the root canals giving branches to the peripheries Branching: - within the coronal pulp chamber Location: - subodontoblastic capillary plexus (within and beneath odonto) - base mem Anastomoses: - arterio-venous and venous-venous Lymph vessels Vasoconstrictor nerve endings in association with arteriole smooth muscle Blood flow 2-60ml/min per 100g of tissue (high fluid Pa)

Question 39

Dentino-pulpal complex - dental pulp - nerve fibres (axons, myelination, fibre type, structure, enter)

Answer 39

Axons: - 2500 enter a mature premolar Myelination: - 25% myelinated afferents Fibres: - 90% of which are Adelta fibres - Adelta thin myelinated axons with a moderate conduction velocity (assoc with acute pain and temp Pa) - remainder are Abeta fibres - afferent fibres that carry non-noxious sensations - unmyelinated C fibres majority (slow conduction, chronic or dull pain with sensations of warmth, mechanical and chemical) Enter: - as part of the neurovascular bundle - branches end in and around odonto layer - plexus beneath odonto (Raschkow)

Question 40

Dentino-pulpal complex - dental pulp - nerve fibres (branches, facilitates, vasodil)

Answer 40

``` Branches: - enter dentinal tubules - many axons in tubules, at peripheries of dentine and among odonto bodies are devoid of schwann - facilitates response to stimuli Vasodilator: - CGRP is potent vasodilator - control pulpal blood flow - synth by neurons and transported by axons - control hard tissue form - nerve in pulp maintain local environ ```

Question 41

Dentino-pulpal complex - dental pulp - regions?

Answer 41

Regions: - supraodonto region - odonto layer - subodontoblastic (cell free zone of Weil and cell rich zone) - Bulk of pulp

Question 42

Dentino-pulpal complex - dental pulp - supraodonto region (location, appear due, axons, tubules)

Answer 42

Location: - between odontoblastic cell bodies and the predentine Appear due: - to tissue shrinkage Axons: - unsheathed axons are present (predentinal plexus of Bradlaw) Tubules: - where changes in tubules can be detected

Question 43

Dentino-pulpal complex - dental pulp - Cell free zone of Weil (processes, location)

Answer 43

Processes: - fibroblasts, odonto, axons and capillaries - anuclear zone - only in coronal pulp of erupted teeth

Question 44

Dentino-pulpal complex - dental pulp - cell rich zone (plexus, cell associated)

Answer 44

``` Plexuses: - subodontoblastic capillary plexus - subodontoblastic neural plexus Cell associated: - with these plexi could result in the richness of this zone ```

Question 45

Dentino-pulpal complex - dental pulp - bulk of pulp (description)

Answer 45

Description: - central area of pulp - loose CT - rich blood and nerve supply

Question 46

Dentino-pulpal complex - dental pulp - ageing of pulp? (what occurs, calcification)

Answer 46

``` Ageing of pulp: - pulpal size decreases - decreased vascularity - more fibrous - reduced innervation Calcification: - pulp stones ```

Question 47

Dentino-pulpal complex - dental pulp - pulp stones (#, denticles, attached, complications)?

Answer 47

Pulp stones: - single or groups - true denticles resemble dentine (tubular) - false denticles resemble bone (trapped cells) - stones attached to dentine - complication of root canal therapy

Question 48

Dentino-pulpal complex - dental pulp - clinical considerations?

Answer 48

Clinical considerations: - defects mediate through pulp - pulp inflamm (pain and difficult to localise) - exposure of lateral canals to the oral environ - exposure to cavity prep - root canal treatment - transformation into granulation tissue following trauma, leading to resorption to dentine by odonto - internal resorp of pulp - pinkish colouration of tooth