Amelogenesis

Question 1

Enamel tissue is a composite ___ mineral with ___ crystals oriented in a complex three dimensional pattern.

Answer 1

biological; apatite

Question 2

T/F. Amelogenesis occurs before dentinogenesis.

Answer 2

False, amelogenesis occurs AFTER dentinogenesis

Question 3

During what stage of odontogenesis does amelogenesis occur?

Answer 3

the crown stage

Question 4

Explain reciprocal induction as it relates to amelogenesis.

Answer 4

Dentin must be present for enamel to be formed and ameloblast must be present in order for dentinogenesis to occur.

Question 5

In ___ ___, epithelial cells from the enamel ___ and ___ cells from the dental papilla interact.

Answer 5

reciprocal induction, organ; mesenchymal

Question 6

T/F. Unlike the other 3 mineralized tissues, enamel does not have an unmineralized preenamel phase.

Answer 6

True.

Question 7

What is the first step of amelogenesis?

Answer 7

secretion of an inmature or partially mineralized (30% inorganic and 70% organic and water) enamel

Question 8

During the second step of amelogenesis, there is a influx of additional mineral conincident with the removal of organic material and water. Therefore, this phase is know as the ___ phase.

Answer 8

maturative

Question 9

What three things are needed for enamel formation (and the other 3 mineralized tissues)?

Answer 9

ameloblast
alkaline phosphatase
rich blood supply

Question 10

Where do ameloblast differentiate?

Answer 10

in the inner cells of the enamel organ

Question 11

Where is alkaline phosphatase located?

Answer 11

in the stratum intermedium layer of the enamel organ

Question 12

where is the rich blood supply located?

Answer 12

in the dental follicle part of the tooth germ

Question 13

During amelogenesis, cells at the ___ most area of the ___ layer of the enamel organ are the first to differentiate into ameloblasts. This process continues apically toward the ___ ___ of the enamel organ.

Answer 13

coronal; inner; cervical loop

Question 14

What are the two phases of the presecretory stage of amelogenesis?

Answer 14

1. morphogenetic

2. histodifferentiation

Question 15

During the ___ stage of tooth development, the shape of the crown is determined at the enamel ___. This represents the ___ phase of amelogenesis.

Answer 15

bell; knot; morphogenetic

Question 16

In the morphogenetic phase, there is a ___ or ___ layer seen between the inner cells of the enamel organ and the peripheral cells of the dental papilla.

Answer 16

clear; acellular

Question 17

During the ___ phase of amelogenesis, the inner enamel ___ cells differentiate into tall ___ ameloblasts. Their nuclei shift proximally toward the ___ ___.

Answer 17

histodifferentiation; epithelial; columnar; striatum intermedium

Question 18

What cells is found at the distal end of the ameloblast?

Answer 18

odontoblasts

Question 19

T/F. At the coronal area of the tooth germ, the ameloblasts and odontoblast interact limiting the clear layer that exists more inferiorly toward the cervical loop. This layer will disppear as the amelogenesis continues apically.

Answer 19

True.

Question 20

What are the six phases of the secretory phase?

Answer 20

1. inner immediately mineralized secretion
2. interrod substance secretion
3. rod secretion
4. maturation phase
5. outer immediately minteralized secretion
6. final ameloblast secretion

Question 21

The inner ___ phase is an ___-___ layer of inner ___ or strucureless enamel that immediately ___ upon secretion.

Answer 21

mineralized; ultra-thin; rodless; mineralized

Question 22

What type of dentin is adjacent to the inner rodless enamel layer?

Answer 22

mantle layer of dentin

Question 23

What happens during the interrod substance phase?

Answer 23

the distal end of the ameloblast changes from a smooth to a configuration termed Tomes’ process

Question 24

___ processes of adjacent ameloblast secrete the ___ ___ that encircles this process.

Answer 24

Tomes’; interrod substance

Question 25

What is the space that initally occupied by Tomes’ process termed?

Answer 25

Tomes’ pit

Question 26

Interrod substance is partially mineralized. What is its composition?

Answer 26

70% organic and water

30% inorganic

Question 27

What surrounds the wall of Tomes’ pits?

Answer 27

interrod substance

Question 28

T/F. Tomes’ process stays as the ameloblast moves toward the future enamel surface. The processes turn into rods.

Answer 28

False, Tomes’ process moves out as the ameloblast move toward the future enamel surface. As the process withdraws, it secretes a partially mineralized rod into the pit.

Question 29

What indicates that the ameloblasts are in the rod secretory phase?

Answer 29

the presence of Tomes’ pocesses and partially mineralized enamel

Question 30

During the maturation phase, what happens to the distal end of the ameloblast?

Answer 30

it alternates between an even, smooth edge and an uneven, ruffled edge

Question 31

What happens when the edge of the ameloblast is even?

Answer 31

They are resorbing or removing organic material and water

Question 32

What happens when the edge of the ameloblast is uneven or ruffled?

Answer 32

They are secreting mineral salts (inorganic) int to the partially mineralized zone

Question 33

When is maturation complete?

Answer 33

When the inorganic materail reaches 96%, organic reaches 1% and water becomes 3%.

Question 34

During the alteration of the ameloblasts border during the maturation process, ___ ___ are no longer present.

Answer 34

Tomes’ processes

Question 35

T/F. The inner, but not outer rodless enamel are mineralized immediately and not secreted by Tomes’ processes.

Answer 35

False, BOTH the inner and outer rodless enamel are mineralized immediately and not secreted by Tomes’ processes.

Question 36

Why does the inner and outer rodless enamel not contain enamel rods?

Answer 36

they are not secreted by Tomes’ processes, which lay down the enamel rod

Question 37

T/F. The outer mineralized phase is the last mineralized secretion of the ameloblasts but not its final secretion.

Answer 37

True.

Question 38

What is secreted during the final ameloblast secretion phase?

Answer 38

the basal lamina

Question 39

Is the basal lamina, mineralized or unmineralized?

Answer 39

unmineralized

Question 40

What is the one phase of the postsecretory stage?

Answer 40

protection phase

Question 41

What is the role of the reduced enamel epithelium?

Answer 41

remnant of the enamel organ and protector of enamel until tooth enters oral cavity

Question 42

What forms the reduced enamel epithelium?

Answer 42

When the four cell layers of the enamel organ come together

Question 43

What does the reduced enamel epithelium become during the emergence of the tooth from the oral cavity?

Answer 43

the junctional epithelium

Question 44

How is the reduced enamel epithelium attached to the enamel surface?

Answer 44

by the basal lamina, the final secretion of the ameloblast

Question 45

How long is the maturation phase, for each permanent tooth, from initiation to completion?

Answer 45

5 years

Question 46

Immature enamel has a ___% organic and water and ___% inorganic make-up.

Answer 46

70; 30

Question 47

What is the timeline for initial mineralization and completed mineralization for all primary teeth?

Answer 47

initial mineralization: 15 - 19 week IU

completed mineralization: 2 - 11 months PN

Question 48

What is the timeline for initial mineralization and completed mineralization for all permanent teeth?

Answer 48

initial mineralization: birth - 9 years

completed mineralization: 5 - 14 years