Histology: Tooth Development

Question 1

Name the 6 Stages of Tooth Development and the aproximate time table for when each stage occurs.

Answer 1

1. Initiation Stage 6th-7th week of development
2. Bud Stage 8th week
3. Cap Stage 9th-10th week
4. Bell Stage 11th-12th week

Terminal Differentiation

5. Apposition Stage varies per tooth
6. Maturation Stage varies per tooth

Question 2

Dental lamina grows deep into the __________

Answer 2

ectomesenchyme

“Before birth, it is called ectomesenchyme. After birth, it is called epithelium”.

Question 3

tooth development is reffered to as?

Answer 3

odontogenesis

Question 4

vestibular lamina proliferates into _______, and then degenerates to form a ______.

Answer 4

mesenchyme

cleft=vestibule

Question 5

Localized proliferations of the ____________ into the surrounding ____________ forms the intitial tooth buds.

Answer 5

dental lamina

mesenchyme

Question 6

Describe the Bud Stage

Answer 6

• initial stage of definitive tooth development
• round localized cluster of oral epithelium of the dental lamina

Question 7

Describe the Cap Stage

Answer 7

• beginning of morphogenesis
• oral epithelium forms a cap over a mesenchymal condensation forms the dental papilla

Question 8

Describe the Bell Stage

Answer 8

• histodifferentiation
• epithelial cells differentiate into ameloblasts
• cells within the dental papilla differentiate into odontoblasts
• eventual shape of crown becomes distinct

dental lamina breaks up into discrete islands

developing tooth is now separate from the overlying oral epithelium

Question 9

Describe the Termination (Crown) Phase

Answer 9

• final differentiation of odontoblasts and ameloblasts
• secretion of dentin and enamel in apposition
• Hard tissue formation of the teeth
  
  • Dentinogenesis
  • Amelogenesis (enamel formation)
• Dental follicle differentiates into alveolar bone forming around the tooth germ

Question 10

Rooth Sheath development is intitiated in the _______

Answer 10

cervical loop region

Question 11

Describe Root Formation

Answer 11

• Epithelial cells from the inner and outer dental epithelium proliferate from the cervical loop of the enamel organ to form Hertwig’s Epithelial Root Sheath.
• The root sheath extends down to encompass all but the basal portion of the pulp
• Ectomesenchymal cells of the pulp which face the root sheath differentiate to form odontoblasts
• The odontoblasts will eventually form root dentin.

Question 12

Epithelial cells from the inner and outer dental epithelium proliferate from the cervical loop of the enamel organ to form ___________.

Answer 12

Hertwig’s Epithelial Root Sheath (HERS)

Question 13

Root development begins after the enamel and dentin formation has reached the future _________.

Answer 13

cementoenamel junction

Question 14

What determines the morphological characteristics of the root (number of roots, length, curvature etc)?

Answer 14

HERS (Hertwig’s Epithelial Root Sheath)

Question 15

Ectomesenchymal cells of the pulp which face the root sheath differentiate to form _______

Answer 15

odontoblasts

Question 16

Odontoblasts will form _______.

Answer 16

root dentin

Question 17

The root sheath encompasses everything except the _________of the pulp.

Answer 17

basal portion of the pulp

Question 18

The ________ differentiates into alveolar bone forming around the tooth germ.

Answer 18

dental follicle

Question 19

The tooth originally develops from _______, a specialized region of ________?

Answer 19

dental lamina

oral ectoderm

Question 20

Tooth development begins with the formation of a continuous band of thickened ______ called _______.

Answer 20

oral epithelium

Primary Epitheliual Band

Question 21

Describe the primary epithelial band

Answer 21

• a continuous band of thickened oral epithelium
• tooth development begins with its formation
• formed by a change in the orientation of mitotic spindles and their increased proliferation activity.
• subdiivides into 2 areas that ingrow the underlying mesenchyme colonized by neural crest
  
  • 1st- dental lamina
  • 2nd- vestibular lamina

Question 22

______ develops lateral to Dental Lamina and will become the ______.

Answer 22

Vestibular Lamina

oral vestibule

Question 23

What is the oral vestibule and from which tissue does it develop?

Answer 23

• the cleft between the cheeks and the tooth-bearing area
• develops from the vestibular lamina

Question 24

The dental lamina gives rise to ______by localized proliferation of the ________ into the surrounding _________, through a continuous process known as ______.

Answer 24

• teeth
• epithelium
• mesenchyme
• odontogenesis

Question 25

Name the stage of odontogenesis and identify each number

Answer 25

Bud Stage 1. Tooth bud 2. Oral epithelium 3. Ectomesenchyme

Question 26

Describe which stage occurs during the 8th week of development

Answer 26

* Teeth begin to develop * Formation of tooth bud. * Cells proliferate. * Neural crest cells migrate to 10 deciduous tooth sites along the future upper and lower jaws. * These cells induce the overlying oral epithelium, or ectoderm, to become a tooth forming organ, the tooth bud.

Question 27

Describe the stage of tooth development that occurs in the 9th week of development

Answer 27

* **Early Cap Stage** * Each tooth bud undergoes a downward growth to form an epithelial structure called the **enamel organ** that is cap shaped. * Histo-differentiation occurs. * The tooth germ also begins to take on form – the start of morpho-differentiation.

Question 28

Identify the Stage and the labeled aspects

Answer 28

Early Cap Stage 9th week 1. enamel organ 2. Dental Papilla 3. Dental sac (dental follicle) All 3 make up the Tooth Germ Note: The tooth bud differentiates further to form the tooth germ.

Question 29

Describe the Stage of Tooth Development that begins in the 10th week of development

Answer 29

Late Cap Stage * Enamel organ produces future enamel. * Dental papilla produces future dentin and pulp. * Basement membrane separates enamel organ and dental papilla to form future DEJ * Remaining ectomesenchyme around the enamel organ will form dental sac, cementum, PDL, alveolar bone.

Question 30

Name the 2 cell types the tooth bud originates from

Answer 30

Ectoderm Ectomesenchyme.

Question 31

Name the 6 cell types the tooth germ originates from

Answer 31

The first 4 epithelium derived from the enamel organ 1. Outer Enamel Epithelium (OEE) - forms the outer border 2. Stellate Reticulum - forms the middle portion 3. Stratum Intermedium - a border of cells between the Stellate Reticulum and Inner Enamel Epithelium. 4. Inner Enamel Epithelium (IEE) - forms the inner border. 5. DP: Dental papilla (dentinogenesis) 6. DF: Dental follicle (sac) (periodontal ligament, alveolus, cementum)

Question 32

Inner Enamel epithelium is composed of functional cells that will differentiate into __________ and make future \_\_\_\_\_\_\_\_\_.

Answer 32

ameleoblasts enamel

Question 33

Within the dental papilla, cells near the Inner Enamel Epithelium will differentiate into _______ to make future \_\_\_\_\_\_. The remaining cells in the dental papilla will form \_\_\_\_\_\_.

Answer 33

odontoblasts dentin dental pulp

Question 34

As we transition from Cap to Bell stage, which 2 newly formed cells can be identified.

Answer 34

Ameloblasts and Odontoblasts Also start to see in the bell stage, the columnar shape of IEE to form Ameloblasts.

Question 35

WHich 2 major events occur during the 11th week of development or early bell stage.

Answer 35

Defining feature of early bell stage= tooth germ assumes a bell-like shape * Enamel Organ differentiates into 4 types of cells 1. Inner dental epithelium-forms future ameloblasts 2. Outer dental epithelium 3. Stellate reticulum 4. Stratum intermedium * Dental papilla differentiates to 2 types of cells: 1. Outer cells of the DP – forms future odontoblasts 2. Central cells of the DP – forms future pulp

Question 36

The entire dental organ is made of epithelial tissue and is avascular. Describe how it obtains nutrients to grow and develop into enamel.

Answer 36

The nutrients must come from the supporting cells. Forming enamel requires a lot of energy, that is why Stellate Reticulum, Stratum Intermedium, and Outer Enamel Epithelium help supply nutrients to the developing Ameloblasts (from Inner Enamel/ Dental Epithelium). - Stellate Reticulum has a large cytoplasm, where it stores nutrients and resources. Also between the dental papila and the Inner Enamel Epithelium is a basement membrane (cell-free zone)