Tooth development

Question 1

What are the two layers that guide organogenesis

Answer 1

It is the epithelial-mesenchymal interactions (reciprocity)

Question 2

Name 4 things that develop from the cranial neural crest cells?

Answer 2

Dentin, Pulp, Cementum, and Periodontal ligaments

Question 3

What is the first thing you see in tooth development?

Answer 3

A thickening of the epithelium called the primary band

Question 4

Which direction does the primary band grow?

Answer 4

Downward towards the ectomesenchyme

Question 5

What are dental placodes?

Answer 5

They mark the places for future tooth development

Question 6

Next to the dental lamina there is another lamina, what is it?

Answer 6

The vestibular lamina

Question 7

What are the 6 steps in crown development?

Answer 7

Initiation, bud, cap, bell, apposition, and maturation

Question 8

What does the ectomesenchyme come from?

Answer 8

Cranial neural crest cells

Question 9

What provides the shape of the developing tooth?

Answer 9

There is cell proliferation at different locations and at different rate

Question 10

During what two stages is the epithelium in control of what is happening?

Answer 10

Primary epithelial band and bud stage

Question 11

In what stage does the inductive influence change over to the mesenchyme?

Answer 11

In the cap stage

Question 12

What are the 4 layers that make up the enamel organ?

Answer 12

OEEs, stellate reticulum, stratum intermedium, and IEEs. These are all present in the bell stage

Question 13

What is the stellate reticulum and the stratum intermedium rich in?

Answer 13

GAGs and Alkaline Phosphatase respectively

Question 14

What makes up the tooth germ?

Answer 14

enamel organ, dental papilla, and the dental sac

Question 15

Where does the successional dental lamina grow?

Answer 15

Always on the lingual side

Question 16

What is an enamel knot?

Answer 16

It is a structure that is located in the enamel organ and tells the cells to slow/stop dividing. So they give shape to the developing tooth and their formation is controlled by the mesenchyme

Question 17

What is another name for the dental sac?

Answer 17

Dental follicle

Question 18

What makes up the cervical loop?

Answer 18

OEEs and IEEs. It is where they meet and is the future sight of the CEJ

Question 19

What is the function of the OEEs?

Answer 19

They form a protective barrier for the enamel organ

Question 20

What is the function of the stellate reticulum?

Answer 20

They support enamel production

Question 21

What is the function of the stratum intermedium?

Answer 21

Supports enamel mineralization (alkaline phosphatases)

Question 22

What is the function of the IEEs?

Answer 22

They become ameloblasts-enamel forming cells

Question 23

What is the order of reciprocal induction in the crown development in the apposition stage?

Answer 23

Enamel knots are formed, the slowing of proliferation caused IEEs to differentiate into preameloblasts, this then causes the outer dental papilla cells to organize and differentiate into preodontoblasts followed by odontoblasts. They then lay down pre-dentin which causes the preameloblasts to become ameloblasts which then lay down enamel.

Question 24

What are Tome’s processes?

Answer 24

They are like odontoblast processes but in enamel and they get mineralized.

Question 25

When does the DEJ form?

Answer 25

After the basement membrane disintegrates between the ameloblasts and odontoblasts

Question 26

How is dentin and enamel played down?

Answer 26

In layers (waves) like the rings on a tree

Question 27

When is the REE (reduced enamel epithelium) formed?

Answer 27

After complete maturation of the enamel

Question 28

What make up the REE?

Answer 28

It is the IEEs, OEEs, and what is left from the other two layers

Question 29

What is the initial layer of dentin right next to the DEJ called?

Answer 29

Mantle dentin

Question 30

What is responsible for root formation?

Answer 30

Hertwig's epithelial root sheath

Question 31

What makes up the HERS (hertwig's root sheath)

Answer 31

OEEs and IEEs

Question 32

The IEEs of the HERS cause what?

Answer 32

Cells in the dental papilla to become odontoblasts that lay down radicular dentin

Question 33

The REEs grow in an apical direction at the cervical loop and become what?

Answer 33

HERS (Hertwig's Epithelial Root Sheath)

Question 34

After radicular dentin is formed what happens to the HERS?

Answer 34

It disintegrates and some become remain and become epithelial rests of Malassez

Question 35

What causes the formation of cementoblasts?

Answer 35

After the HERS has disintegrated and dental sac cells migrate in and come in contact with the root dentin and that is what causes the dental sac cells to differentiate into cementoblasts

Question 36

What happens to the cementoblasts in the apical 1/2-1/3 of the cementum?

Answer 36

They get entrapped and become cementocytes like in bone

Question 37

What gives rise the shape of the root and how many will form?

Answer 37

Unequal proliferation of the HERS, just like what gives shape to the crown of the tooth

Question 38

How are the PDLs formed?

Answer 38

Ectomesenchyme cells from the dental sac differentiate into fibroblasts that secrete collagen, which become anchored into the cementum

Question 39

How is alveolar bone formed?

Answer 39

From the ectomesenchyme cells of the dental sac, PDLs are also anchored into it as well