Maya - Dental Pulp Biology and Odontogenesis: Development, Anatomy, Innervation, and Pathology

Operative 2 Exam

What embryonic cells are the origin of the oral cavity and teeth?

Neural crest cells, which give rise to the dental lamina

List the stages of odontogenesis in order. (6)

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Which forms first, dentin or enamel?

Bud →

Cap →

Bell →

Dentinogenesis →

Amelogenesis →

Appositional dentin and enamel →

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Dentin forms first (dentinogenesis occurs before amelogenesis)

Morpho-differentiation vs. histo-differentiation?

Morpho: development of the shape; crown develops first (tooth forms crown-down)

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Histo: differentiation at the cellular level

"What structures are labeled in the histo-differentiation (bell stage) photomicrograph?

When does root formation occur, and what are the 3 primordial root terms?

"After dentinogenesis and amelogenesis

1. Cervical loop
2. Hertwig's epithelial root sheath
3. Epithelial root diaphragm

How do the cell rests of Malassez form, and what is their clinical significance?

"Epithelial root sheath breaks up → dental sac CT contacts dentin → forms cementoblasts and PDL

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Epithelial cells left in the PDL = cell rests of Malassez
Can form lateral periodontal cysts later in life

Lateral vs. accessory canals: location, function, contents, and endo management?

Lateral: coronal 2/3; accessory: apical 1/3 (increased here)

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Direct contact between pulp and PDL

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Do NOT contain pulp tissue

• Sealed during obturation

What are the 2 ways lateral/accessory canals form?

1. Break in the root sheath before dentin forms

2. Blood vessel traveling between dental sac and dental papilla

What is the accessory canal opening into the furcation of a multirooted tooth called?

Furcal canal

What is cementum?

Hard tissue that covers the root; where the PDL attaches

What is the apical foramen, how far is it offset from the apex, and what does it contain?

Opening at the end of the root where pulp contacts PDL

• Offset 0.5-1 mm

• Contains the neurovascular bundle

What is the apical foramen's size in a mature tooth, and how does it change with age?

0.3-0.6 mm

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Changes location and gets smaller due to cementum deposition

What is an apical delta?

An apical foramen with several accessory canals

What are the 3 histologic components of the pulp?

1. Cells

2. Fibers

3. Ground substance

List the layers of the pulp-dentin complex from dentin inward (6)

Dentin →

Predentin →

Odontoblastic layer →

Cell-free (cell-poor) zone →

Cell-rich zone →

Central pulp (pulp proper)

What is in each zone of the pulp?

Odontoblastic layer: odontoblasts lining predentin

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Cell-free: no cells

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Cell-rich: undifferentiated mesenchymal cells, fibroblasts, blood vessels, defense cells

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Pulp proper: central core

List the 6 cells of the healthy pulp.

1. Fibroblasts

2. Mesenchymal cells

3. Odontoblasts

4. Histiocytes

5. Dendritic cells

6. Lymphocytes

Pulpal fibroblasts: prevalence, location, and products?

Most common pulp cell

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Mostly in the cell-rich layer

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Produce collagen (I and III) and ground substance

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• Per lecture notes: differentiate into odontoblasts that make dentin

Odontoblasts: uniqueness, product, parts, and connections?

Unique to pulp; produce dentin

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Cell body + Tomes' (odontoblastic) process, which extends into dentin to the DEJ

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Joined by desmosome-like junctions

How do odontoblast shape and organization vary by region?

Coronal: columnar, most organized

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Middle 1/3 (mid-root): cuboidal, well organized (just above cell-rich zone)

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Apical: squamous, least organized

What are pulpal defense cells, and what irritants trigger them?

Cells of the inflammatory response in the pulp due to an irritant

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Irritants: caries, trauma, operative procedures

What is pulpal ground substance like, and what is its function?

Similar to connective tissue

• a glycoprotein medium

• Transports nutrients and oxygen

Pulpal fibers: collagen types, sources, elastic fibers, and distribution?

Dentin: type I (odontoblast)

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Pulp: types I and III (fibroblast)

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No elastic fibers (still being investigated)
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Apical region has the most collagen

What are the components of the pulpal extracellular matrix, and what do tenascin and fibronectin do? (3)

1. Water

2. Glycosaminoglycans,

3. Collagen (I, III),

4. non-collagenous proteins (tenascin, fibronectin): - - Tenascin/fibronectin: substrate adhesion glycoproteins for cell attachment, spreading, and migration

Describe the pulpal nerve supply (fiber types, locations, efferent function).

Afferent sensory: A-delta (peripheral pulp), C fibers (central pulp)

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Efferent motor: sympathetic (parasympathetic questionable) → smooth muscle contraction

Characteristics and associated diagnosis of A-delta fibers (slide titled ""A(alpha)"")?

Low threshold, myelinated, high conduction velocity
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At the pulp-dentin border (peripheral)

• Sharp, lightning, non-lingering pain → Reversible pulpitis

Characteristics and associated diagnosis of C fibers?

High threshold, non-myelinated, low conduction velocity

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• Through the central pulp

• Throbbing, dull, lingering, poorly localized pain
  → (Symptomatic) irreversible pulpitis; needs endodontic therapy

If pulpal nerves extend only 100-200 µm into dentin, why does drilling just past the DEJ hurt?

Sensory nerves can extend into the dentinal tubule alongside Tomes' process

What are the 3 theories of dentin sensitivity, and which is most common?

1. Direct innervation: nerve fibers in the tubule

2. Odontoblastic receptor: nerves and odontoblasts are close

3. Hydrodynamic (most common): fluid movement in tubules triggers nerves; basis of thermal testing

Pulpal arterial supply: importance, origin, and branches?

Determines vitality

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Origin: internal maxillary artery

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Branches: posterior, middle, and anterior superior alveolar; inferior alveolar

How do arterioles enter and travel through the pulp, and where are vessels most numerous?

Enter through the apical foramen and lateral canals, course toward the crown

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Most numerous in the subodontoblastic zone

Pulpal venous return: drainage, vein features, exit, and where flow is greatest?

Drains to pterygoid plexus and internal maxillary vein

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Veins: larger, not innervated, thin walled; A-V shunts present

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Exit through apical foramen and lateral canals

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Blood flow greatest in coronal pulp

What are the functions of pulpal A-V shunts? (2)

1. Bypass the capillary bed during inflammation → ↓ intrapulpal BP

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2. Help control normal pulpal vasculature

In the pulpal microcirculation, what bypasses the true capillaries, and what controls entry into them?

A-V shunt connects arteriole to venule

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Precapillary sphincters (open/closed) control capillary entry

What are the 5 functions of the pulp, and which is most important?

1) Induction: produces predentin; stimulates initial ameloblast formation
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2) Formation: continuously forms secondary dentin (most important)
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3) Nutrition: dentinal fluid nourishes dentin
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4) Defense: forms reparative (tertiary) dentin in response to irritant
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5) Innervation: innervates dentin

What are the age changes of the pulp?

Calcification of chamber and canals → smaller canals

• Blood vessels and nerves decrease and mineralize

• Collagen and reticular fibers form bundles

• Diffuse and localized calcification

Is pulpal calcification (e.g., pulp stones) correlated with symptoms?

No; it is not an indication for RCT

What are the 2 types of pulpal calcification and where does each occur?

Pulp stones (denticles): chamber

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Diffuse/linear: radicular (canals), along nerves, vessels, or collagen bundles

How are pulp stones classified? (5)

1) True: smooth;

2) False: concentric layers

3) Free: in chamber;

4) Attached: to chamber wall;

5) Embedded: in chamber wall

What is the immune response to small, large, and prolonged carious exposures?

Small: APCs, random migration of T cells
Large: PMNs, B-cell activation
Prolonged: specific T cells in effector phase eliminate bacteria

Why is the pulp called a non-compliant environment?

Tooth is hard and non-expandable, so it can't swell → intrapulpal pressure increases

What immune cells are in the inflamed pulp?

PMNs; T, B, and NK cells

• Plasma cells making IgG and IgA against microbes in the carious lesion

What is the key message about carious pulp exposures?

By the time there is a carious exposure, it's too late (necrosis) → endo tx or extraction

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Do NOT direct pulp cap a carious exposure

What were the outcomes of direct pulp caps on carious exposures in Barthel 2000?

5 yr: 45% failure, 18% questionable, 37% success

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10 yr: 80% failure, 7% questionable, 13% success

How does the pulp respond to a deep cavity prep, and what is the usual outcome?

Normal pulp (a)

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Odontoblasts destroyed, acute inflammation, cell division in the cell-rich zone (b)

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Pulp recovers in the vast majority (c), with reparative dentin

How is any dental procedure (e.g., crown prep) viewed pulpally?

As iatrogenic trauma that can cause reversible pulpitis

What factors in full-coverage restoration can lead to pulp involvement?

Prep: frictional heat, vibration, desiccation

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After prep: cleansing/sterilization, acid etching, impressions, restorative materials, insertion and cementation, marginal leakage → Pulpal inflammation → necrosis

What are the 2 categories of pulpal reactions?

Vascular and neural

Due to the pulp's low compliance, what sequence leads to necrosis? (5)

↑ Blood flow →

↑ tissue pressure →

↓ blood flow (stasis) →

toxic metabolites →

localized necrosis (→ RCT or extraction)

What causes the rise in intrapulpal pressure, and why does it lead to necrosis?

Vascular permeability, cellular infiltrate, vascular stasis

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Pulp in rigid walls → stasis and microabscess → necrosis

What are the 4 defense mechanisms of the pulp?

1. AV shunting
2. Secondary dentinal mechanisms
3. Reactionary and reparative dentin formation
4. Immune reactions

How does pulpal blood flow respond to an insult such as grinding?

↑ Flow through AV shunts and redistribution of flow

Secondary vs. reactionary/reparative dentin: when does each form?

Secondary: physiological, throughout life

Reactionary/reparative: in response to an irritant

Where does reparative dentin form, and how does it affect pulp space?

Under large restorations; pulp horns, canal, and chamber shrink