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DMD2 > The Pulpodentine Complex 1 > Flashcards

The Pulpodentine Complex 1 Flashcards

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1
Q

What are the immune cells in the dental pulp?

A

Dendritic cells (antigen presentation)

Macrophages (antigen presentation and

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2
Q

What is endodontics defined as?

A

The branch of dentistry concerned with the morphology, physiology, and pathology of the human dental pulp.

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3
Q

What do dental placodes do?

A

Dental placodes act on overlying dental ectomesenchyme to initiate formation of the tooth.

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4
Q

What do dental placodes do?

A

Dental placodes act on overlying dental ectomesenchyme to initiate formation of the tooth. It is located within the dental lamina.

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5
Q

Where are dental placodes located?

A

They are located within the dental lamina.

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6
Q

When does odontogenesis begin in primary and permanent dentition?

A

Primary dentition: 5th week of gestation

Permanent dentition: 14th week of gestation

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7
Q

What happens during the lamina stage of odontogenesis?

A

The basement membrane between the oral epithelium and the ectomesenchyme pinches into the ectomesenchyme.

Epithelial cells change in orientation with the mitotic spindles and cleavage planes of dividing cells not increasing proliferative activity.

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8
Q

What happens during the cap stage of odontogenesis?

A

Dental lamina grows to encompass the ectomesenchyme growth forming a cap.

Condensed ectomesenchyme becomes the dental papilla

The epithelium cap becomes the enamel organ.

The surrounding condensed ectomesenchyme becomes the dental follicle

The enamel knot is formed which is a critical signalling center within the epithelium which regulates crown morphogenesis.

Cervical loop starts to form for future root formation.

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9
Q

What happens during the bell stage of odontogenesis?

A

Continuous growth of the tooth germ makes it appear like a bell. Cells continue to divide but at different rates.

The crown assumes its final shape in the early bells stage.

Morphodifferentation where the ameloblasts and odontoblasts acquire their distinct phenotype in the late bell stage.

HIstodifferentiation

Formation of secondary enamel knots which are critical signalling centers and are located on future sites of the cusps.

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10
Q

What is the function of the basement membrane?

A

It is the epithelial mesenchyme interface which is an interface between the inner enamel epithelium and the ectomesenchyme.

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11
Q

What is the basement membrane made from?

A

The composition of the basement membrane changes and this modulates the successive steps in odontogenesis.

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12
Q

Where does dentinogenesis begin?

A

First occurs at the future cusp tip / incisal edge.

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13
Q

What happens when Hertwig’s Root Sheath is developed?

A

Stellate reticulum and stratum intermedium cells disappear.

It acts as a barrier between the dental papilla and dental follicle cells.

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14
Q

What does Hertwig’s Root Sheath do?

A

It is a barrier between the dental papilla and dental follicle cells.

Determines the shape, size, and number of roots.

Involved in the development of root dentine and cementum.

Induces the differentiation of odontoblasts from the dental papilla

Induces the differentiation of cementoblasts from the dental follicles.

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15
Q

What happens to mesenchymal cells from the follicle that come into contact with hertwig’s epithelial root sheath?

A

They differentiate into cementoblasts

Cementum is deposited on root dentine. (epithelial cells of malassez end up here)

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16
Q

How are accessory/Furcation canals form?

A

Entrapment of periodontal vessels in Hertwig’s epithelial root sheath during mineralization.

Furcation: Entrapment during the fusion of the diaphragm which becomes the pulp chamber floor.

Pathway for irritants from the root canal to the lateral periodontium.

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17
Q

What are the morphological zones of the pulp?

A

Odontoblast layer (Contains odontoblasts)

Cell-poor zone (contains lots of blood and nerve vessels)

Cell-rich zone (contains immune cells and fibroblasts)

Pulp proper (contains stem cells and plasma cells)

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18
Q

What does the odontoblast layer of the dental pulp contain?

A

Outmost layer is lined by a single layer of cell bodies.

Immediate subjacent to the predentine and contains:

Odontoblast cell bodies.

Capillaries

Terminal nerve axons

Dendritic cells

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19
Q

What does the Cell-poor zone layer of the dental pulp contain?

A

It is relatively free of cells. Instead it contains:

Rich capillary plexus

Plexus of raschkow (rich network of unmyelinated nerve fibers)

Slender cytoplasmic processes of fibroblasts

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20
Q

How does size and shape of odontoblasts vary in the pulp?

A

Coronal pulp has tall and columnar odontoblasts

Mid root has cuboidal odontoblast cells.

Near apical foramen the cells appear more flattened.

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21
Q

What is contained in the cell rich zone?

A

Fibroblasts

Undifferentiated mesenchymal stem cells

Immune cells like macrohages and dendritic cells (More prominent in coronal pulp)

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22
Q

What is contained in the pulp proper?

A

Fibroblasts

Large blood vessels

Nerve axon bundles

Undifferentiated mesenchymal cells

Immune cells (macrophages, dendritic cells, lymphocytes)

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23
Q

What does the connective tissue of the dental pulp contain?

A

Cells

Extracelular matrix

Blood vessels and nerves.

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24
Q

What do odontoblasts do in the dental pulp?

A

They are the most specialized cells they are:

Dentine forming (unique cell produces unique tissue)

Cell processes in the dentine tubules (Makes dentine a living, responsibe tissue)

Fixed post mitotic cell that is fully differentiated.

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25
What do odontoblasts do in the dental pulp?
They are the most specialized cells they are: Dentine forming (unique cell produces unique tissue)
26
When does the dental pulp contain odontoblasts?
They are always present, they survive for the life of the tooth.
27
How are odontoblasts unique?
Cell processes in the dentine tubules extend a considerable distance from the dentinal tubules (Makes dentine a living, responsibe tissue) They have cell bodies and reside outside the mineralized matrix They are fixed post mitotic cells that are fully differentiated.
28
What cells do odontoblasts resemble most and how?
Osteoblasts: They have a cell body that stays close to the process
29
What are the cytological features of ordontoblasts?
Similar to other secretory cells: HIghly ordered rough ER in parallel stacks aligned to the length of the cell Prominent golgi complex Secretory granules (move to apical areas and into odontoblast processes) Numerous mitochondria One or more nucleoli
30
How are odontoblasts organized?
They are a highly polarized cell: Synthesis occurs in the cell body Secretion occurs from the cell process Matrix secretion precedes mineralization and are separated in time and space by predentine.
31
How are odontoblasts connected to each other?
Desmosomes are responsible for cell-to-cell spot adhesion for mechanical join. They are located in the apical part of the cell body. Gap junctions at different levels of cell bodies that are important for intercellular communication (regulate activity and synchronize secretion) they also join odontoblasts to fibroblasts Tight junctions are located on the apical part of the cell body. This forms a predentine-pulp barrier.
32
What does the predentine-pulp barrier do?
Restricts passage of molecules into the pulp. Determines the permeability of the odontoblast layer when dentine is covered by enamel / cementum.
33
What happens to odontoblasts as they age?
Morphology reflects functional state and with time the aging odontoblasts change in the following ways: They become progressively shorter Less polarized Decreased in number and size of organelles Final stage leads to organelles being located within the intranuclear region and the supernuclear regions become devoid of organelles except for large lipid filled vacuoles
34
What are the functions of the dental pulp?
Secretory: Forms and maintains dentine Sensory: Affected by outside antigens, mechanical forces, and thermal gradients. Pain mediator: Acts as a transducer between external stimuli and pulp sensory nerves (neuromodulation)
35
What are the immune functions of odontoblasts?
They are the first to encounter antigens diffusing along the dentinal tubules and contains microbial pattern recognition receptors (TLRs for example) They release pro-inflammatory cytokines They release chemokines to attract and activate dendritic cells
36
What is the function of fibroblasts?
They are most numerous in the pulp (particularly in the cell rich zone) Produce and maintain extracellular matrix Participate in signalling pathway in inflammation
37
Where are undifferentiated mesenchymal cells located most prominently?
They are present throughout the pulp (densest in the pulp core, perivascular area) They migrate to areas of injury and replace destroyed odontoblasts in response to migratory signals.
38
What are the features of undifferentiated mesenchymal cells?
They are multipotent and differentiate into odontoblast like cells producing dentine like structure. They can self renew. They form one identical to parent cell and the other is more differentiated and odontoblast like.
39
What immune cells are present in the dental pulp?
Dendritic cells Macrophages Lymphoctes
40
What do dendritic cells do in the pulp?
They are most prominent and are present as 2 populations: One that is in/subjacent to the odontoblast layer, and the other that is around blood vessels with migratory ability. Immuno surveillance: APCs which constantly express MHCII complexes on surface Induce T cell immune
41
Where are macrophages located in the pulp?
Located in the central pulp predominant in proximity to the bv in normal healthy pulp resting as monocytes.
42
What is the function of macrophages?
Immuno surveillance: APCs, require stimulation by bacteria or cytokines fro expressing MHCII Active in phagocytosis Induce T cell immunity Activate signalling pathways in inflammation.
43
Where are lymphocytes located in the dental pulp?
T8 suppressors are predominant T4 helpers together with APCs
44
What is the extracellular matrix of dental pulp composed of?
Collagen fibers type 1 and 3 Ground substances such as proteoglycans and hyaluronan Interstitial fluid
45
Where is collagen of the extracellular matrix most common?
Near the apex
46
Which type of collagen is the main form?
Type 1 (type 3 is the foetal form in dental papillae and pulp)
47
What does the hydrogel component of extracellular matrix do to the pulp?
Determines the pulp physical characters (it is highly hydrated) Supports cells (transport medium for nutrients and wastes as well as physically protecting the tooth via cushioning) Acts as a molecular sieve. (Regulates diffusion of substances and excludes large proteins)
48
What does proteoglycan in the pulp do?
It acts as a protein core with covalently attached Glycosaminoglycan chains Adhesive for cells / molecules Provides tissue turgor Mediates cell interactions
49
What are the physical properties of hyaluronan?
Consists of unbranched random-coil large polymers Unique in no sulfate Non-covalently formed complexes with proteoglycans. High viscosity even at low concentration Strong affinity for water
50
What does interstitial fluid do?
Transports medium for nutrients and waste products between cells and capillary blood
51
What kind of encasement does the pulp have?
The pulp has a rigid - low compliance case
52
What are the dentine boundaries?
The dentinoenamel junction in the crown where the dentin meets the enamel The dentinocemenal junction where the dentine meets the cementum.
53
What structure is located at the apex of the root of the tooth?
The apical foramen/constriction
54
What are the components of the extracellular matrix?
Collagen proteins make up 90% of the protein including type 1 collagen (high level collagen cross-linking which provide tensile strength to support the brittle enamel) Non-collagenous proteins make up 10% of the proteins and include proteoglycans (provide tensile strength) and glycoproteins (Dentine phosphoprotein (critical for dentine mineralisation) Enzymes such as matrix metalloproteinases (degrade almost all ECM components) Insulin like growth factors (IGFs locally stimulate stem cell differentiation) Albumin, IgG
55
How does extracellular matrix hold the minerals?
Hydroxyapatite crystals fill up the collagen matrix (type 1). The collagen acts as a scaffold for non-collagenous protein mineralization within collagen fibrils and between collagen fibrils. (Intra and interfibrillar mineralization) Calcospherites are globules of hydroxyapatite located in the mineralised front between predentine and mineralised dentine. As calcospherites enlarge they fuse with adjacent ones until dentine matrix is completely mineralised.
56
What fluid is contained in the extracellular matrix?
Dentinal fluid which is an ultrafiltrate of blood from the pulp capillaries. (Composition resembles plasma with less proteins and higher ionized calcium concentration)
57
What happens to dentinal fluid if dentine is exposed?
There is a slow outward flow of fluid.
58
What kind of nerves go to the pulp of the teeth?
Sensory afferent nerves and terminal nerve axons.
59
How is dentine structure organized?
Dentine is penetrated by millions of tubules which extend through the entire thickness of dentine. The density of these tubules varies: Less near the DEJ and more near the pulp. The dentinal tubules are tapered in structure; they are narrower at the dentinoenamel junction and wider near the pulp. The dentinal tubules are extensively branched. They have branches of the main odontoblast processes. This acts as a pathway for movement of materials between the main processes and the more distal matrix. (more frequently in root dentine and more prominent at dentinoenamel junction)
60
How are dentinal tubules organized?
S-shaped in coronal dentine and straight in root dentine due to the course taken by odontoblasts during dentinogenesis from DEJ towards pulp.
61
How dense are the dentinal tubules near the DEJ?
2 - 3% of SA
62
How dense are the dentinal tubules near the pulp?
22 - 45%
63
Does predentine have any peritubular dentine?
No peritubular dentine in predentine
64
Where is the branching of the dentinal tubules more prominent and common?
More frequently in root dentine More prominent at the DEJ Significantly higher at the cuspal area Significantly higher in the cuspal area and more sensitive which provides increased pulp dentine defence against abrasion/attrition
65
How are dentinal tubules organised at early stages of dentinogenesis?
Newly differentiating odontoblasts extend several small cytoplasmic processes towards the DEJ. As odontoblasts migrate, their processes converge into one major process.
66
What is the structure of odontoblast processes like?
They extend from cell body into the predentine/dentine. They are extremely fine like a capillary tube with a low diameter. Gradually narrowing from pulp to the DEJ They lack cell organelles but contain secretory vacuoles. They are abundant in microtubules and microfilaments. (important infrastructure for transportation.
67
How long is the the odontoblast process into the dentine?
Light microscope shows the processes extend from the cell body to the dentinoenamel junction (2 - 3mm) Electron microscopy shows it limited to the inner third of dentine (1mm) This made scientists confused so they used cryofixation to prevent contraction before observing it to reach the DEJ. Conclusion is it reaches the DEJ
68
What do odontoblast processes do?
They make dentine a living tissue by secreting collagen and non-collagenous proteins for dentine formation They produce peritubular dentine which narrows tubule diameter by forming a hypermineralized cuff.
69
Where is intertubular dentine located?
Located between tubules and constitues the bulk of dentine and is the primary formative product of odontoblasts
70
What is intertubular dentine composed of?
Mainly collagen fibrils (Tightly interwoven in a network that is randomly in a plane at approximately right angles to the tubules) Well mineralized with apatite crystals that provide tensile strength to dentine
71
Where is peritubular dentine located?
It is deposited on the inner surface of the tubular wall only after the formation of the intertubular dentine.
72
How is peritubular dentine differentiated from intratubular dentine?
It is sharply demarcated from the intertubular dentine
73
Is rate of formation of peritubular dentine constant?
No, it can be accelerated during irritation / stimulation.
74
What does peritubular dentine consist of?
It is more highly mineralized than intertubular dentine and consists of a mineralized 'collar'. Collagen poor (less collagen fibrils) Rich in non-collagenous proteins and sulfated proteoglycans Mineral rich and harder
75
How are peritubular and intertubular dentine different in structure?
Peritubular dentine is 5x harder than ID and consists of a homogenous non-fibrillar matrix Intertubular is more fibrillar, collagenous, and has a matrix appearance. Peritubular dentine is more quickly dissolved in acid than intertubular dentine.
76
What is the purpose of acid etching in restorative procedures?
EDTAC irrigation is used to preferentially remove the peritubular dentine. Enlarges the opening of the dentinal tubules Makes dentine more permeable.
77
What acid is used for acid etching?
EDTAC
78
Which type of dentine is missing in predentine?
Peritubular dentine
79
What are the 2 levels of matrix secretion from the odontoblasts?
At the proximal level: Collagen Proteoglycans These accumulatein predentine At the distal level: Tissue specific non-collagenous matrix Proteoglycans (more sulfated: chondroitin sulfate)
80
What happens in sclerotic dentine?
Dentinal tubules are filled with mineral deposits. This increases with age.
81
Where is sclerotic dentine most common?
In the apical third of the root In the crown midway between the dentinoenamel junction and the pulp.
82
What effect does scelrotic dentine have on dentine?
Reduces dentine's permeability which may reduce formation of tertiary dentine.
83
What are the types of mineral deposits that occlude tubules in sclerotic dentine?
Physiological (peritubular dentine deposition) Diffuse mineralization (with a viable odontoblast process) Intraluminal crystalline deposit Mineralization of the process itself and tubular contents
84
What effect does intraluminal crystalline deposit have on the dentine?
Makes it almost impermeable
85
What is interglobular dentine?
Forms when growing calcospherites fail to fuse into a homogenous mass within mature dentine. This results in hypo or unmineralized areas of dentine. *Usually located just below the mantle dentine
86
What causes formation of interglobular dentine?
Hypo or unmineralised areas are formed when calcospherites fail to fuse into a homogenous mass within mature dentine. It is a defect in mineralization not of matrix formation.
87
What is defective in interglobular dentine?
Mineralization is defective. Matrix formation is not affected so dentinal tubules run continuously uninterrupted but no peritubular dentine.
88
Where is mantle dentine located?
Right under the crown (it is the first formed dentine)
89
Where is primary dentine located?
Primary dentine fills the tooth just under the mantle dentine and outside the boundary of the pulp. Pulp boundary is surrounded by secondary dentine and predentine.
90
How are collagen fibers arranged in mantle dentine?
Characteristic thick, fan-shaped collagen fibers in an irregular matrix loosely packed as coarse collage fibrils.
91
How is mineralization different in mantle dentine?
It is slightly less mineralised than the underlying primary dentine. It also lacks dentine phosphoprotein making it regulate crystal growth in circumpulpal dentine.
92
How does mantle dentine influenze mineralisation?
Mineralization occurs through matrix vessels which are small and closed by a membrane. They are rich in enzymes such as adenosine triphosphate and phosphohydrolytic enzymes. Rupture to be starting points for mineralization.
93
Where is predentine located?
Between the odontoblast layer and the mineralized dentine. (innermost to the pulp)
94
What does predentine consist of?
Newly secreted dentine with unmineralized organic matrix as well as proteins and growth factors.
95
When is primary dentine formed?
Prior to eruption and prior to the completion of the apical root growth.
96
What is the structure of primary dentine like?
It constitutes major part of the dentine (outlines pulp chamber / root canal system AND circumpulpal dentine surrounding the secondary dentine) It is regular in structure consisting of dentinal tubules in an S-shaped primary curvature.
97
How is primary dentine produced?
It is the primary secretory product of the primary odontoblasts. *Secondary dentine is also produced by primary odontoblasts
98
Where is secondary dentine produced?
Asymmetrically on floor and roof of the pulp chamber. Walls of the root canal.
99
Where is secondary dentine located?
Fills entire pulp chamber of the crown and extends down to the apical third of the root canal.
100
How is the structure of secondary dentine different to primary dentine?
It is less regular in structure but tubules are continuous with primary tubules. This is because it is formed by downregulated primary odontoblasts. Tubules change direction slightly.
101
What is the purpose of tertiary dentine?
It is the pulp's unique defence response to injury.
102
How is tertiary dentine produced?
It is produced by injured odontoblasts or replacement odontoblasts to reduce dentine permeability.
103
What is the structure of tertiary dentine like?
It is disorganized in structure with variable appearance depending on intensity and duration of the injury. It is regular and tubular It is dysplastic and atubular (newly formed odontoblasts may lack processes)
104
Where is a dentine bridge usually produced? What is the dentine bridge?
At the site of pulp exposure. It is reparative dentine with tunnel defects
105
When are the different types of dentine formed?
Primary dentine is prior to eruption Secondary dentine is after eruption Tertiary dentine is in response to injury.

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