L2

Question 1

Odontogenesis:

Answer 1

The formation of tooth tissues from
stem cells originating in the
ectoderm primary germ layer

Question 2

3Odontogenesis begins in the

Answer 2

sixth embryonic week

Question 3

Two basic tissues that arise from the ectoderm primary germ layer are involved in tooth development

Answer 3

:epithelium and mesenchyme

These odontogenic tissues contain stem cells that become the
specialized cells that form tooth tissues

Question 4

Dentinogenesis:

Answer 4

formation of dentin tissue

Question 5

Amelogenesis:

Answer 5

formation of enamel tissue

Question 6

Cementogenesis:

Answer 6

formation of cementum tissue

Question 7

Pulp: This was what part of the tooth germ and
what 2 formative (blast) cell types arose
from its stem cells?

Answer 7

Dental papilla: Odontoblast: Fibroblast

Question 8

Periodontal Lig. This was what part of the tooth germ and
what 3 formative (blast) cell types arose
from its stem cells?

Answer 8

Dental follicle: Fibroblast: Cementoblast: Osteoblast

Question 9

Fate of cervical loop part of enamel organ:

Answer 9

Outer and inner layers come together, at the cervical loop, forming a double epithelial layer called
Hertwig’s epithelial root sheath

Question 10

Hertwig’s epithelial root sheath

main functions

Answer 10

The sheath serves 2 main functions:

             1. Determines root dentin outline
             2. Determines number of root canals of tooth

Question 11

Cervical Loop

Answer 11

rim of the epithelial bell (enamel organ)

- site where inner and outer cell layers merge (meet)

Question 12

Fate of enamel organ cell layers after completion over enamel:

Answer 12

The 4 cell layers of enamel organ come together to form a stratified epithelial layer over the enamel surface called ‘reduced enamel epithelium’ that protects the enamel from surrounding connective tissue until the tooth enters the oral cavity

Question 13

3 parts of Tooth Germ:

Answer 13

Enamel organ, Dental Papilla, dental follicle

Question 14

Enamel organ:

Answer 14

(avascular)
* Inner epithelial cells differentiate into ameloblasts – specialized epithelial cells
* After the formation of enamel is complete, the ameloblasts, along with the other
layers of the enamel organ come together over the surface of the enamel
as a protective structure called: ‘reduced enamel epithelium’

Question 15

Dental papilla: (vascular)

Answer 15

Its undifferentiated cells (stem cells) become odontoblast, fibroblast, reserve cells
* Ultimately becomes pulp tissue of tooth

Question 16

Dental follicle:

Answer 16

(vascular)

• Its stem cells become cementoblast, fibroblast, osteoblast, and reserve cells
• Ultimately becomes periodontal ligament of the periodontium

Question 17

the enamel organ is attached to both mesenchymal parts of the tooth germ by
a

Answer 17

basal lamina

Question 18

Tooth Germ:

Answer 18

The epithelial enamel organ and a closely associated ectomesenchymal tissue that is continuous from around the epithelium to within the epithelium:
Combined, these tissues are called a Tooth Germ

Question 19

Secondary Dental Lamina

Answer 19

Secondary dental lamina (arrow) is lingual to primary tooth germ:
Ten secondary lamina arise in each arch; one for each secondary tooth

Question 20

Secondary dental lamina

arises from the

Answer 20

primary dental lamina

NOT the oral epithelium

Question 21

Bell Stage (enamel organ)
At this stage

Answer 21

4 distinct epithelial cell layers of the enamel organ are recognized,
as marked in the image

Question 22

Four distinct epithelial cell layers of the enamel organ

Answer 22

1= Inner epithelial layer;
2= Stratum intermedium epithelial layer
3= Stellate reticulum epithelial layer
4= Outer epithelial layer

Question 23

Cap stage:

Answer 23

Note site of enamel knot (encircled) concentration of epithelial cells of cap that is a signaling center: determines if tooth will develop to become an anterior or posterior tooth:

Question 24

Note: a total of 16 epithelial buds arise from the

Answer 24

primary dental lamina
of each arch: 10 primary teeth and 6 permanent molars
*

Question 25

Also note: each succedaneous tooth has its own

Answer 25

secondary dental lamina that
arises from the lingual side of the primary dental lamina:
(Total of 10 secondary dental laminae in each arch)

Question 26

Primary buds: (Timeline: 6 to 8 weeks in utero)

Answer 26

Central incisors:.. 6 weeks in utero

Second molars:… 8 weeks in utero

Question 27

Permanent buds: (Timeline 4 months in utero to 5 years postnatal)

Answer 27

First molar: ….. 4 months in utero
Central incisor: …5 months in utero
Second molar: … 10 months postnatally
Third molar: ….. 5 years postnatally

Question 28

Note epithelial bud cells

are continuous with cells of

Answer 28

primary dental lamina

Question 29

Vestibular lamina:

Answer 29

band of epithelial cells: lies

facial to developing tooth site

Question 30

Epithelial Bud Stage- primary dental lamina

Answer 30

Cells at the deep end of the dental lamina, where a tooth is destined to
form, will develop into epithelial knobs, each know as an ‘epithelial bud’
Each epithelial bud is surrounded by mesenchymal tissue
PDL = primary dental lamina; VL = vestibular lamina

Question 31

Fate of the 2 invaginated bands of epithelium:

Answer 31

The facial most epithelial band is the:
- vestibular lamina:
Cell death will occur in the center of the vestibular lamina,
leaving a space known as the ‘vestibule’
* The lingual most epithelial band is the
- primary dental lamina (odontogenic epithelium):
Cells arising from the dental laminae
become the odontogenic epithelial part of a Tooth Germ

Question 32

1 Primary Dental Lamina Stage:

Answer 32

During the 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 invaginations descend into the underlying mesenchymal tissue (ectomesenchyme) and continue posteriorly within the mesenchyme as continuous epithelial bands
* facial band is called: vestibular lamina
* lingual band is called: primary dental lamina

Question 33

Epithelial Stages: based on histologic shapes of the epithelial tissue
within a mesenchymal tissue environment

Answer 33

1 = epithelial dental lamina stage
2 = epithelial bud stage
3 = epithelial cap stage
4 = epithelial bell stage (enamel organ):
(at the bell stage the epithelium is arranged
in 4 distinct layers:

Question 34

Tooth Germ Stage:

Answer 34

Odontogenic epithelial and mesenchymal tissues combined:
Cells of each tissue induced specifically to become
formative cells of dentin, enamel, cementum and pulp tissues
Three parts of Tooth Germ:
1 Enamel Organ (Bell): epithelium
2 Dental Papilla: mesenchyme
3 Dental Follicle: mesenchyme

Cells from these 3 parts give rise
to the specialized cells that
form tooth tissues

Question 35

Dentin forms

Answer 35

first, then enamel, then cementum, then pulp

Question 36

Salivary glands form from

Answer 36

ectoderm

Question 37

Meckel’s cartilage

Answer 37

becomes jaw.

Question 38

Vestibular lamina

Answer 38

becomes vestibule

Question 39

Primary dental lamina connected to

Answer 39

basal lamina always

Question 40

Trigeminal ganglion

Answer 40

V3

Question 41

Bottom of epithelial bud

Answer 41

from neural crest (condensed cells)