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Oral histology > Tooth Development > Flashcards

Tooth Development Flashcards

1
Q

What is the Crown?

A

Part of tooth covered w/enamel
Provide chewing surface

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2
Q

What is the Root?

A

Part of tooth covered with cementum and embedded in the jaw
Supports the crown

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3
Q

Periodontium includes?

A

Cementum
Alveolar bone
Periodontal Ligament

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4
Q

List the Crown Formation Stages

A
  1. Dental Lamina Stage
  2. Bud stage
  3. Cap stage
  4. Bell stage
  5. Apposition stage
  6. Maturation stage
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5
Q

What is Proliferation?

A

Cell dividing

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6
Q

What is Differentiation?

A

Cells stop dividing (if still dividing it won’t specialize!)
Undergo morphological changes, then acquire functional assignments
Ex. a cell becoming an odontoblast

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7
Q

What is Morphogenensis?

A

Establishment of shape and size of future tooth
Achieved by differential growth

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8
Q

Explain the Dental Lamina Stage

A
  • Ectomesenchyme cell induce oral epithelium which creates horseshoe-shaped ridges along both jaws
  • Successional dental lamina
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9
Q

Explain the Bud Stage

A
  • Proliferation of DL epithelial cells at 10 locations on each ridge, which makes tooth buds
    * Tooth buds: early enamel organs
  • Ectomesenchyme begins to condense around epithelial bud
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10
Q

Explain the Cap Stage:

A
  • Morphodifferentiation
    - unequal proliferation of bud cells (cap)
  • Ectomesenchymal cells become dental papilla (DP) and dental sac (DS)
  • Creation of the tooth germ
  • Succesional dental lamina forms on LINGUAL side of DL
  • Cytodifferentiation
    - four layers of enamel organ
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11
Q

What is a tooth germ?

A

Present in Cap Stage
enamel organ + dental papilla + dental sac

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12
Q

What does the enamel organ form?

A

Forms Enamel
Epithelial component of tooth germ

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13
Q

What does the dental papilla form?

A

Forms Dentin and Pulp
Derived from neural crest cells

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14
Q

What does the dental sac form?

A

Forms cementum, alveolar bone and periodontal ligament (basically forms the periodontium!)
Derived from neural crest cells

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15
Q

Explain the Bell Stage:

A
  • Cont. differentiation of enamel organ that produces 4 distinct layers with different functions
  • Creation of cervical loop
  • Dental papilla cells continue to proliferate & they develop into the OUTER and INNER dental papilla cells
  • Dental sac cells continue to proliferate & they develop into periodontal tissues
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16
Q

What are the 4 distinct layers the enamel organ produces in the Bell Stage?

A

Inner enamel epithelium
Stratum intermedium
Stellate reticulum
Outer enamel epithelium

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17
Q

Inner enamel organ (IEE) function

A
  • Differentiate into ameloblasts (enamel forming cells)
  • Induce the differentiation of adjacent cells of dental papilla into odontoblasts
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18
Q

Stratum Intermediate function

A

A layer of spindle-shaped cells adjacent to IEE cells.
Supports enamel mineralization - alkaline phosphatase

19
Q

Stellate reticulum function

A
  • Cells secrete glycosaminoglycans (GAG).
  • GAG’s draw water into enamel organ increasing its volume.
20
Q

Outer enamel epithelium (OEE) function

A
  • Protective outer barrier for enamel organ.
  • Associated with** capillary plexus**.
21
Q

What is the cervical loop?

A

Junction of OEE and IEE

22
Q

Explain the Apposition Stage:

A
  • Matrix of enamel and dentin are laid down followed by initial calcification
  • Reciprocal inductions between enamel organ and dental papilla occur in specific order (1-7)
23
Q

Apposition/Ameloblast Functional Phases (in order!!!)

A
  1. Morphogenetic (IEE)
    - IEE to preameloblasts
  2. Differentiation
    - Preameloblasts to preodontoblasts to odontoblasts
  3. Initial Secretory ameloblast
    - Odontoblasts to predentin and signals preameloblasts to create secretory ameloblasts
  4. Secretory ameloblast
    - Secretory ameloblasts begin secreting enamel matrix which calcifies to 30% ASAP
  5. Ruffle-ended Maturation Ameloblast
  6. Smooth-ended Maturation Ameloblast
  7. Protective ameloblast
24
Q

What is Reduced enamel epithelium? (REE)

A
  • Composed of the ISSO parts from Bell Stage!!
    - Composed of flattened ameloblasts and the leftover 3 layers from enamel organ
    - Covers and protects enamel
25
Q

List and Explain Stages of Dentinogenesis

A
  1. Mantle Dentin
    *1st formed layer of dentin from newly differentiated odontoblasts
    *Collagen fibers are perpendicular to DEJ
  2. Circumpulpal Dentin
    * Dentin beneath the mantle dentin
    * Collagen fibers are smaller in diameter and randomly oriented
26
Q

List and explain the 2 types of dentin (phases) in Dentinogenesis

A
  1. Pre-dentin
    * Layer of organic collagen matrix
    * Unmineralized (if unmineralized ALWAYS pre-dentin)
  2. Dentin
    * Organic collagen matrix
    *Hydroxyapatite crystals
27
Q

Patterns of Dentin Mineralization

A

Globular Mineralization
Linear Mineralization

28
Q

What is Globular Mineralization?

A

Calcophospherites grow and coalesce (unite)
Irregular mineralization front
Rate of dentin deposition is FAST

29
Q

Calcophospherites are what?

A

Spherical foci of hydroxyapatite

30
Q

What is Linear Mineralization?

A

More uniform mineralization front
Rate of dentin deposition is SLOW

31
Q

What 2 things need to happen in order for root formation to occur?

A

Dentinogenesis
Cementogenesis

32
Q

Root Formation (Maturation)
What does the Reduced Enamel Epithelium grow into after apical growth? How is it formed and what is it’s purpose?

A

Hertwig’s Epithelial Root Sheath
- Formed by: the joining of the IEE and the OEE
- Purpose: Shapes the root of the tooth and the formation of root dentin from odontoblasts

33
Q

Root Formation (Maturation)
At what angle does the epithelial root sheeth proliferate?

A

Coronally at the angle of the epithelial diaphragm, but NOT at its tip because at the end is where proliferation is still occuring!

34
Q

Root Formation (Maturation)
T/F: The epithelial diaphragm does NOT maintain a constant size during root formation

A

False!
The epithelial diaphragm DOES maintain a constant size

35
Q

Root Formation (Maturation)
What does the remnants of HERS become?

A

Malassez’s epithelial rests

36
Q

What is the difference between cementoid and cementum?

A

Cementoid: NOT mineralized
Cementum: mineralized

37
Q

What is multiple root formation?

A
  • Occurs when medial ingrowths or invaginations of the HERS
  • The number of roots is determined by the number of medial ingrowths!
38
Q

What is cementogenesis?

A
  • Creation of cementum
  • Occurs after the first layer of dentin is depositied and the cervical portion of Herwig’s root sheath breaks down
  • Cementum is then deposited incrementally
  • Creation order goes like this:
    - Ectomesenchymal cells (dental sac cells) & new dentin contact
    - Ectomesenchymal cells form cementoblasts, which then form cementum
39
Q

What are the 2 types of fiber cementum formed during Cementogenesis? List their characteristics

A

Cellular intrinsic fiber cementum
- Secondary cementum: deposited AFTER tooth eruption
- Contains cementocytes
- Forms RAPIDLY
Acellular extrinsic fiber cementum
- Primary cementum: deposited during tooth eruption
- NO cementocytes
- Forms SLOWLY

40
Q

What are the 3 types of Root Anomalies?

A

Exposed root dentin
Enamel pearls
Accessory root canals

41
Q

Root Anomalies
Explain what exposed root dentin is

A
  • An area of root dentin lacking cementum
  • Occurs when epithelial root sheath remains attached to root dentin surface
  • Ectomesenchymal cells won’t come into contact with root dentin so no cementoblasts will be created!
  • Can be found anywhere along the root surface, particularly the cervical zone
42
Q

Root Anomalies
Explain what enamel pearls are!

A
  • An enamel droplet often found between the roots of permanent molars
  • Formed when the epithelial root sheath remains attached to the root dentin surface
  • Cells of the inner layer of the root sheath can differentiate into ameloblasts and form this
43
Q

Root Anomalies
Explain what accesory root canals are!

A
  • A small lateral canal (connecting PDL to main root canal)
  • Formed if epithelial root sheath breaks down before root dentin is formed
  • No ectomesenchymal cells (epithelial root sheath) to differentiate into odontoblasts= no root dentin formation
  • Can be found anywhere along the root, particularly in the apical third or furcation area of multirooted teeth

Oral histology (4 decks)

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