Lecture 2- odontogenesis

Question 1

Odontogenesis begins at what week?

Answer 1

6th week of embryonic development

Question 2

2 basic tissues that arise from ectoderm primary germ layer that play a role in tooth development

Answer 2

epithelial and mesenchymal

Question 3

odontogenic tissues contain

Answer 3

stem cells that become the specialized cells that form tooth structures

Question 4

Epithelial stages of odontogenesis
based on?
what are they?

Answer 4

based on histological shape of epithelial tissues in mesenchymal cell environment

1. epithelial dental lamina stage
2. Bud stage
3. cap stage
4. Bell stage (with enamel organ that has four layers)

Question 5

Tooth germ stage

3 parts of tooth germ? derived from what tissue?

Answer 5

odontogenic epithelial and mesenchymal tissues are combined
-cells of each tissue induced to become cells of enamel dentin, pulp, cementum

Enamel organ (epithelial)
Dental papilla (mesenchyme)
Dental follicle (mesenchyme)
-cells from these 3 parts give rise to specialized cells to form tooth structures

Question 6

Description of first primary dental lamina stage

Answer 6

-At 6th week of development 2 invaginations of epithelial cellsappear anteriorly in mandibular region amongst ectomesenchymal cells. They continue to move on posteriorly and form a facial vestibular lamina band and a lingual primary dental lamina band

Question 7

facial most epithelial band is the

Answer 7

vestibular lamina

Question 8

What occurs to form the vestibules

Answer 8

cell death in the center of the facial/vestibular lamina

Question 9

Lingual most epithelial band is the

Answer 9

primary dental lamina

Question 10

primary dental lamina becomes

Answer 10

become odontogenic epithelial portion of the tooth germ

Question 11

cells at deep end of dental lamina will form

Answer 11

epithelial bud surrounded by mesenchymal tissue

Question 12

primary buds form during?

What teeth do the primary buds form and when?

Answer 12

6 to 8 weeks in utero
Central incisors (6 weeks)
2nd molars (8 weeks)

Question 13

When do permanent buds form?

What teeth do the permanent buds form and when?

Answer 13

4 months in utero to 5 years postnatally

First molar (4 months in utero)
Central incisor (5 months in utero)
Second molar (10 months post natally)
Third molar (5 years post natally)

Question 14

How many buds arise from the primary dental lamina

Answer 14

16 epithelial buds with 6 for permanent molars and 10 for primary teeth

Question 15

each succedaneous tooth has

Answer 15

a secondary dental lamina attached to it coming from the lingual side of the primary dental lamina

Question 16

enamel knot of cap stage is site of

Answer 16

densely full of epithelial cells that signal whether a tooth will become an anterior or posterior tooth

Question 17

at the bell stage epithelial tissue is aligned in how many layers and what are they

Answer 17

4 tissue cell layers

1. Inner epithelial layer
2. stratum intermediuum
3. stellate reticulum
4. outer epithelial layer

Question 18

secondary dental lamina arises from the

Answer 18

primary dental lamina and not the oral epithelial tissue

Question 19

Enamel organ forms what

vascular?

Answer 19

Inner epithelial cells differentiate into ameloblasts

• after formation of enamel is complete, ameloblasts as well as other enamel organ layers come together to form a protective layer called the reduced enamel epithelium
• enamel organ is avascularized

Question 20

Dental Papilla becomes

vascularized?

Answer 20

Odontoblasts, fibroblasts, reserve cells
-ultimately becomes pulp tissue of tooth

It is vascularized

Question 21

Dental follicle becomes

vascularized?

Answer 21

cementoblast, fibroblast, osteoblast, and reserve cells
periodontal ligament of the tooth
it is vascularized

Question 22

how is the enamel organ attached to both mesenchymal parts

Answer 22

via the basal lamina

Question 23

Odontoblasts and ameloblasts found in between

Answer 23

Dental papilla and inner epithelial layer of enamel organ
they are tall collumnar epithelial cells
white space between ameloblasts and odontoblasts from the dentinoenamel junction

Question 24

Fate of enamel organ cell layers after completion of enamel formation

Answer 24

Come together to form a stratified epithelial layer called the reduced enamel epithelium to protect the tooth enamel until it enters the oral cavity

Question 25

site where the inner and outer enamel organ cell layers meet

Answer 25

cervical loop

-forms a double epithelial layer called hertwig’s epithelial root sheath

Question 26

function of hertwig’s epithelial root sheath

Answer 26

determines root dentin outline

determines amount of canals in the tooth