Odontogenesis #2

Question 1

What is the definition of Odontogenesis?

Answer 1

Formation of tooth tissues from stem cells originating in the ectoderm primary germ layer.

Question 2

When does Odontogenesis begin?

Answer 2

6th embryonic week

Question 3

What are the two basic tissues that arise from the ectoderm primary germ layer in tooth development?

Answer 3

Epithelium & Mesenchyme

Question 4

What is Dentogenesis?

Answer 4

formation of dentin tissue

Question 5

What is Amelogenesis?

Answer 5

Formation of Enamel tissue

Question 6

What is Cementogenesis?

Answer 6

Formation of cementum

Question 7

What is the first stage of Odontogenesis?

Answer 7

Epithelial stages: based of histological SHAPES of the epithelial tissue.

1. epithelial dental lamia stage
2. Epithelial bud stage
3. epithelial Cap stage
4. Epithelial Bell stage *at this stage the epithelium is arranged in 4 distinct layers.

Question 8

What is the second stage of Odontogenesis?

Answer 8

Tooth germ stage: Ondotogenic epithelial and mesenchymal tissue combined: cells of each tissue induced specifically to become formative cells of dentin, enamel, cementum and pulp tissues.

Question 9

What are the three parts of tooth germ?

Answer 9

1. Enamel organ (bell) epithelium
2. Dental Papilla (Mesenchyme)
3. Dental follicle (Mesenchyme)

Question 10

Briefly describe when and what occurs during the primary dental lamina stage….

Answer 10

• Occurs during 6th embryonic week
  Two epithelial invaginations appear in the lower anterior region of the lower jaw and later in the same week in the upper jaw.
  These two invaginations descend into the underlying mesenchyme tissue and continue posteriorly within the mesenchyme as continuous epithelial bands.
  ** Facial band = vestibular lamina
  ** Lingual band = Primary dental lamina

Question 11

What is the fate of the vestibular lamina (Facial band)?

Answer 11

Cell death will occur in the center of it, leaving a space called a vestibule.

Question 12

What is the fate of the Primary dental lamina (Lingual band)?

Answer 12

cells will become the odontogenic epithelial part of a tooth germ.

Question 13

What occurs during the Epithelial Bud stage?

Answer 13

Cells at the deep end of the dental lamina, (Where tooth is destine to form) will develop into epithelial knobs, each known as “epithelial bud”. *Each epithelial bud is surrounded by mesenchymal tissue:

Question 14

Vestibular lamina band lies _____ to developing tooth site.

Answer 14

Facial

Question 15

Epithelial bud cells are _____ withe the cells of the PDL.

Answer 15

Continous

Question 16

When do Primary (teeth) buds form?

Answer 16

6-8 weeks in utero

• Central incisors = 6 weeks
• Second molars = 8 weeks in utero

Question 17

When do permeant (teeth) buds form?

Answer 17

4 months in utero - 5 years postnatal

• First molar = 4 months in utero
• Central incisor = 5 months in utero
• Second molar = 10 months in utero
• third molar = 5 years postnatal

Question 18

What occurs in the Cap stage?

Answer 18

Odontogenic epithelial tissue is in the shape of a cap.
* Note: Site of enamel knot (concerntraion of epithelial cells in cap) is a signaling center that determines if tooth will develop to become ant. or post. tooth!

Question 19

What occurs in the Epithelial Bell Stage?

Answer 19

Epithelial cap undergoes growth and develops into a bell shaped epithelia structure called an “enamel organ).
* At this point the epithelium is arranged into 4 distinct layers; given names according to position within the bell and the cell morphology.

Question 20

Where do ameloblasts come from?

Answer 20

Enamel organ

Question 21

Where does secondary dental lamina arise from?

Answer 21

Primary dental lamina!

Question 22

What happens in the Enamel organ?

Answer 22

• Avascular
  Inner epithelial cells differentiate into ameloblasts.
  *After formation of enamel, ameloblasts come together over surface of enamel and form a protective structure called reduced enamel epithelium.

Question 23

What happens in the Dental papilla?

Answer 23

* Vascular
Undifferentiated cells (stem cells) become odontoblasts, fibroblasts, reserve cells and ultimately becomes the pulp of tooth.

Question 24

What happens in the Dental follicle?

Answer 24

• Vascular
  Its stem cells become cementoblasts, fibroblasts, osteoblasts and reserve cells. Ultimately forms the periodontal ligaments.

Question 25

________ Protects the enamel from surrounding connective tissue until the tooth enters the oral cavity.

Answer 25

Reduced enamel epithelium formed from the 4 layers of the enamel organ (into a stratified epithelial layer).

Question 26

What is the fate of the cervical lop part of the enamel organ?

Answer 26

Outer and inner layers come together and forum double epithelia layer called Hertwigs epithelial root sheath.

Question 27

What are the 2 functions of Hertwigs epithelial root sheath?

Answer 27

1. Determines root dentin outline

2. Determines number of root canals in tooth.