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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
List and Explain Stages of Dentinogenesis
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
List and explain the 2 types of dentin (phases) in Dentinogenesis
1. **Pre-dentin** * Layer of organic collagen matrix * Unmineralized (if unmineralized ALWAYS pre-dentin) 2. **Dentin** * Organic collagen matrix *Hydroxyapatite crystals
27
Patterns of Dentin Mineralization
Globular Mineralization Linear Mineralization
28
What is Globular Mineralization?
Calcophospherites grow and coalesce (unite) **Irregular** mineralization front Rate of dentin deposition is **FAST**
29
Calcophospherites are what?
Spherical foci of hydroxyapatite
30
What is Linear Mineralization?
More **uniform** mineralization front Rate of dentin deposition is **SLOW**
31
What 2 things need to happen in order for root formation to occur?
Dentinogenesis Cementogenesis
32
Root Formation (Maturation) What does the Reduced Enamel Epithelium grow into after apical growth? How is it formed and what is it's purpose?
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
Root Formation (Maturation) At what angle does the epithelial root sheeth proliferate?
Coronally at the angle of the epithelial diaphragm, but **NOT at its tip** because at the end is where proliferation is still occuring!
34
Root Formation (Maturation) T/F: The epithelial diaphragm does NOT maintain a constant size during root formation
False! The epithelial diaphragm DOES maintain a constant size
35
Root Formation (Maturation) What does the remnants of HERS become?
Malassez's epithelial rests
36
What is the difference between cementoid and cementum?
Cementoid: NOT mineralized Cementum: mineralized
37
What is multiple root formation?
- Occurs when medial ingrowths or invaginations of the HERS - The number of roots is determined by the number of medial ingrowths!
38
What is cementogenesis?
- 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
What are the 2 types of fiber cementum formed during Cementogenesis? List their characteristics
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
What are the 3 types of Root Anomalies?
Exposed root dentin Enamel pearls Accessory root canals
41
Root Anomalies Explain what exposed root dentin is
- 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
Root Anomalies Explain what enamel pearls are!
- 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
Root Anomalies Explain what accesory root canals are!
- 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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