Odontogenesis

Question 1

what are the 4 main tissues in the body?

Answer 1

epithelium, nerves, connective tissue and muscles

Question 2

is the tongue needed for tooth formation?

Answer 2

No, but it is needed for innate qualities

Question 3

when does odontogenesis start?

Answer 3

begins in 6th embryonic week

Question 4

what are the 2 ectoderm derived tissues involved in tooth development?

Answer 4

epithelium and mesenchyme

Question 5

odontogenesis

Answer 5

formation of tooth tissues from stem cells that originate in the ectoderm primary germ layer

Question 6

dentinogenesis

Answer 6

formation of dentin tissue

Question 7

amelogenesis

Answer 7

formation of enamel tissue

Question 8

cementogenesis

Answer 8

formation of cementum tissue

Question 9

what are the formative levels of the odontogenic tissue before the appearance of mineralized tissue (histologically)

Answer 9

1. epithelial stages (around mesenchyme)
   a. epi dental lamina stage
   b. epi bud stage
   c. epi cap stage
   d. epi bell stage (at this stage it is the enamel organ with 4 distinct layers)
2. Tooth germ stage (enamel organ, dental papilla and dental follicle)
   * *dental follicle and papilla are mesenchyme

Question 10

what is the tooth germ stage?

Answer 10

epithelium and mesenchyme combined

Question 11

what occurs in the 6th embryonic week?

Answer 11

anterior invaginations on the lower (upper comes later) jaw of epithelium into the mesenchyme continue posteriorly as epithelial bands

Question 12

what are the names of the facial and lingual epithelial bands

Answer 12

the facial is the vestibular lamina and the lingual is the primary dental lamina

Question 13

what is the fate of the vestibular lamina?

Answer 13

cell death occurs in the center leaving a space known as the vesitble

Question 14

what is the fate of the primary dental lamina?

Answer 14

cells arising from the dental lamina become the odontogenic epithelial part of the tooth germ
**enamel aries from primary dental lamina

Question 15

what connects epithelium to mesenchyme?

Answer 15

basal lamina

ex. enamel organ attached to follicle and papilla

Question 16

epithelial bud

Answer 16

cells in the deep end of the dental lamina will develop into epithelial knobs (buds) that is surrounded by mesenchymal tissue. the bud cells are continuous with the dental lamina cells. Each primary and permanent (6 molars each arch) has its own epithelial bud so there are 16 buds/arch from the primary dental lamina. The upper arch is 1/2 week behind in development.

Question 17

what is the first tissue mineralized in all teeth?

Answer 17

dentin

Question 18

what begins to break up once dentin is mineralized?

Answer 18

primary dental lamina

Question 19

primary bud dates

Answer 19

central incisors is 6 weeks in utero, and 2nd molars are 8 weeks in utero

Question 20

permanent bud dates

Answer 20

first molar is 4 mo. in utero, central incisor is 5 mo. in utero, second molar is 10 mo. postnatally and third molar is 5 years postnatally

Question 21

secondary dental lamina

Answer 21

arises from the lingual side of the primary dental lamina to form the teeth that are succedaneous

Question 22

epithelial cap stage

Answer 22

has an ENAMEL KNOT (a concentration of epithelial cells) that is a signaling center that determines if the tooth will be an anterior or posterior tooth

Question 23

epithelial bell stage

Answer 23

(also in germ layer stage) is the enamel organ that will become almeloblasts
has 4 distinct cell layers : inner epithelial, stratum intermedium epithelial, stellate reticulum epithelium (glyco-protein) and outer epithelial

Question 24

what layer of the enamel organ becomes the ameloblasts?

Answer 24

inner epithelial layer (next to the CT)

Question 25

what makes up the enamel organ?

Answer 25

``` **epithelium and ectomesenchyme that is in and in the epithelium enamel organ (E), dental papilla (M) and dental follicle (M) ```

Question 26

if you switched the mesenchyme of anterior and posterior teeth would they switch and become each other?

Answer 26

yes

Question 27

is epithelium avascular?

Answer 27

YES, all of it

Question 28

what does the enamel organ become?

Answer 28

inner epithelial layer will differentiate into ameloblasts, once enamel formation is complete all 4 layers will come together to form a protective layer called REDUCED ENAMEL EPITHELIUM

Question 29

what does the dental papilla become?

Answer 29

stem cells become odontoblasts, fibroblasts and reserve stem cells **ultimately becomes the pulp

Question 30

dental follicle becomes?

Answer 30

stem cells become cementoblasts, fibroblasts and reserve cells **becomes periodontal ligament

Question 31

what is the hardest mineral in the body?

Answer 31

enamel (hydroxyapitate)

Question 32

what is the point of the reduced enamel epithelium

Answer 32

4 cells layers of the enamel organ come together to form a stratified epithelial layer to protect the enamel from the CT that surrounds it until it erupts in the oral cavity **enamel only wants to contact saliva

Question 33

where do the inner and outer epithelial layers of the enamel organ merge?

Answer 33

at the cervical loop

Question 34

what is the double epithelial layer at the cervical loop called?

Answer 34

hertwigs epithelial root sheath

Question 35

what does hertwigs epithelial root sheath form?

Answer 35

1. root-dentin outline | 2. number of root canals