Tooth and jaw development

Question 1

On an x-ray what are the first visible signs of a developing tooth

Answer 1

Appear as a number of snow capped peaks

Question 2

What happens to a tooth as it begins to erupt?

Answer 2

The roots start to grown with very open apical ends

Question 3

Why can we not see anything on an xray before the snow capped peaks even though the tooth started developing before that?

Answer 3

As there is no mineral involved I early development of a tooth

Question 4

Name the 3 main developmental processes of tooth formation

Answer 4

1. Determination- of position and morphology
2. Initiation
3. Control- of morphology and histodifferentiation

Question 5

What is the aim fo the determination process of tooth development?

Answer 5

To map out where teeth will grow in the mouth and which teeth will grow where
Morphology and position

Question 6

How is tooth development controlled

Answer 6

Via ectodermal and mesenvymal interactions

Question 7

What can interactions between ectodermal and mesenchymal tissue lead to

Answer 7

can up or downregulate:

1. Proliferation
2. Differentiation

Question 8

What happens if ectodermal/ mesenchymal interactions affects proliferation?

Answer 8

Morphogenesis occurs

Question 9

What is morphogenesis?

Answer 9

Formation of crown and root shape

Question 10

What happens if ectodermal/ mesenchymal interactions affects differentiation?

Answer 10

Histodifferentation occurs which leads to tissue formation

Question 11

What is histodifferentiation

Answer 11

The formation of distinct cell populations

Question 12

Name the 3 morphogenic field

Answer 12

1. Incisor field
2. Canine field
3. Molar field

Question 13

What does the ectomesencyme control

Answer 13

What type of tissue will form where and the morphology of the tooth

Question 14

List the recombination experiments that showed the ectomesenchyme controls morphology

Answer 14

Enzymatic separation of the ectoderm and the mesenchyme in both developing molars and canines
They then swapped the mesenchyme tissue so that the molar ectoderm now had canine mesenchyme and canine ectoderm had molar mesenchyme
The result was a canine tooth with molar morphology and molar tooth with canine morphology

Question 15

State the initial stage of tooth development

Answer 15

The primary epithelial band splits into vestibular lamina and dental lamina

Question 16

List the stages of of tooth formation once the dental lamina has formed

Answer 16

1. Bud stage
2. Cap stage
3. Bell stage early
4. Bell stage late
5. Root development

Question 17

What is significant about the late bell stage

Answer 17

It marks the point at which the first mineral is deposited out the cusp of the tooth
Thus the tooth is first visible at this point on an xray

Question 18

What does the primary epithelial band determine

Answer 18

It maps out where the upper and lower dental arches will form

Question 19

As the tooth buds continue to develop what else is happening at the same time?

Answer 19

A plate of bone is forming below the tooth germ- this is the lateral plate of the mandible/ maxilla

Question 20

Where and how does the bone of the jaw form?

Answer 20

The bone of the jaw forms denovo within the mesenchyme

eventually a second medial plate of bone ill develop to form a trough where the tooth germ is contained

Question 21

What is bone formation in the mesenchyme called?

Answer 21

Intramembranous bone formation

Question 22

Name the cartilage found on the mandible

Answer 22

Meckel’s cartridge

Question 23

What happens to Meckel’s cartridge during formation

Answer 23

It plays no direct part in the formation of the main body of the mandible
It eventually disappears and remnants of it contribute to ear ossicles and the speno-mandibular ligament.

Question 24

What happens to the trough of bone where the tooth germ is contained?

Answer 24

it will become sub divided by cross plates of bone to form the individual tickets

Question 25

As the jaw is developing what is happening to the actual tooth?

Answer 25

1. Its enamel organ has started to grow into the beginnings of the cap shape
2. Indications of histogenesis starting
3. Ectomesenchyme has also proliferated to form a dense condensation in and around the enamel organ

Question 26

What does the cap shape mark out?

Answer 26

Marks out where the primary cusps of the tooth will form

Question 27

What is the part enclosed by the enamel organ called

Answer 27

Dental papilla

Question 28

What is the part surrounded by the enamel organ Called

Answer 28

Dental follicle

Question 29

What does the dental papilla eventually form

Answer 29

Dentine and pulp of the tooth

Question 30

What does the dental follicle eventually form

Answer 30

The periodontal ligament and cementum

Possibly some of the alveolar bone

Question 31

Describe the later cap stage

Answer 31

1. Beginnings of the socket are evident (bone surrounds tooth germ)
2. Enamel organ has grown
3. Further histogenesis
4. Inner and outer enamel epithelium has formed
5. Down growth lingually of a breach of the dental lamina

Question 32

What is the inner enamel epithelium

Answer 32

A distinct inner layer of columnar cells

Question 33

What is the outer enamel epithelium

Answer 33

more cuboidal cells forming the ‘outer’ envelope

Question 34

In the later cap stage what is the bulk of the enamel organ made up of

Answer 34

Consists of loose, stellate reticulum

Question 35

Describe the enamel organ in the alter cap stage

Answer 35

1. Bulk made up of loose, stellate reticulum

2. 2 transitionary structure found: enamel knot and enamel septum

Question 36

What is the significance if the enamel knot

Answer 36

May have an important tole in interacting with the mesenchyme in cuspal initiation and initial control

Question 37

What is the significance of the enamel septum

Answer 37

May be a site where cell division is occurring to provide more cells for the stellate reticulum as it enlarges

Question 38

What is the significance of the down growth lingually of a branch of the dental lamina

Answer 38

at the end of it the bud of the permanent tooth that will eventually replace this deciduous tooth develops