Tooth Development

Question 1

What is the dental lamina

Answer 1

• A fold in the developing oral epithelium that gives rise to tooth germs

Question 2

What are the 5 stages of tooth development

Answer 2

1. Bud
2. Cap
3. Bell
4. Crown
5. Root

Question 3

What stages of tooth development happen before mineralisation

Answer 3

1. Bud
2. Cap
3. Bell

Question 4

Give a super brief description of what happens in the bud stage

Answer 4

1st condensation of mesenchyme around epithelium, characterised by appearance of tooth bud with no clear arrangement of cells

Question 5

Give a super brief description of what happens in the cap stage

Answer 5

Enamel organ forms “cap” above the dental papilla

This stage begins once the epithelial cells proliferate into the ectomesenchyme of the jaw

Question 6

Give a super brief description of what happens in the bell stage

Answer 6

Shape of tooth crown begins to emerge in contours of enamel organ

Question 7

Give a super brief description of what happens in the crown stage

Answer 7

Mineralised crown tissue (dentine and enamel) deposition

Question 8

Give a super brief description of what happens in the root stage

Answer 8

Crown formation complete, roots grow, and tooth erupts and root apex matures

Question 9

What is the ectoderm

Answer 9

developmental germ layer that forms skin, oral epithelium, and enamel organ.

Question 10

What is the mesenchyme

Answer 10

loose, migratory, undifferentiated cells that are important in development of many tissues.

Question 11

What is the dental papilla

Answer 11

mesenchyme-derived part of tooth germ.

Question 12

What is the enamel organ

Answer 12

developmental derivative of dental lamina.

Question 13

What is the stellate reticulum

Answer 13

cellular filling of enamel organ

Question 14

What happens in the bud stage of tooth development

Answer 14

• marked by growth of epithelium into the mesenchyme
• period of extensive proliferation and growth of the dental lamina
• dental lamina forms into tooth buds that penetrate into mesenchyme
• each tooth bud is surrounded by the mesenchyme
• buds + mesenchyme develop into tooth germ and associated tissues of the tooth

Question 15

What happens in the cap stage of tooth development

Answer 15

1. Dental lamina expands to form cap-like structure called enamel organ, which continues to grow.
2. Part of mesenchyme is concentrated under cap as dental papilla.
3. Earliest cap stages at 11 weeks.

Question 16

What happens in the bell stage of tooth development

Answer 16

1. Enamel organ tissues begin to differentiate.
2. Enamel organ begins to fold into shape of finished crown.
3. Dental papilla tissues begin to differentiate.
4. First reached at 14 weeks.

Question 17

In the cap stage what forms the cap/enamel organ

Answer 17

A depression that forms in the deepest part of each tooth bud and forms the cap/enamel organ, produces the future enamel

Question 18

What forms under the cap in the cap stage

Answer 18

A condensing mass of mesenchyme - the dental papilla - produces the future dentin and pulp tissue

Question 19

What in the cap stage is the future site of the EDJ

Answer 19

The basement membrane that separates the enamel organ and the dental papilla

Question 20

In the cap stage what does the remaining mesenchyme surrounding the enamel organ form

Answer 20

It condenses to form the dental sac or the dental follicle

Question 21

What does the tooth germ consist of

Answer 21

Enamel Organ
Dental Papilla
Dental Follicle

Question 22

What are the 4 types of cells in the enamel organ

Answer 22

1. inner enamel epithelium (IEE)
2. outer enamel epithelium (OEE)
3. stellate reticulum
4. stratum intermedium

Question 23

What does the dental papilla differentiate into

Answer 23

1. outer cells of the dental papilla - forms the dentin secreting cells (odontoblasts)
2. central cells of the dental papilla - forms the primordial of the pulp

Question 24

What is the function of OEE cells

Answer 24

Protective barrier during the enamel production

Question 25

What do the IEE cells differentiate into

Answer 25

Ameloblasts

Question 26

What is the shape of the stellate reticulum

Answer 26

Star shaped

Question 27

What is the role of the stellate reticulum

Answer 27

supports the production of enamel and produce GAGs

Question 28

What is the role of the stratum intermedium cells

Answer 28

Supports production of enamel

Question 29

How do the cells of the stellate reticulum become star shaped

Answer 29

- cells in the centre of the enamel organ (enamel knot) begin to synthesize and secrete glycosaminoglycans - this pulls water into the enamel organ - increasing amount of fluid, forces the cells apart - however, they remain connected via cellular processes which makes them star shaped

Question 30

How can the primordia of the permanent dentition first be seen

Answer 30

during the cap stage the primordial appears as an extension off the developing dental lamina (site of origin = successional dental lamina)

Question 31

What happens in the appositional stage of tooth development

Answer 31

- Secretion of enamel, dentin and cementum - these tissues are initially secreted as a matrix that is partially calcified – serves as a framework for later calcification

Question 32

What happens in the maturation stage of tooth development

Answer 32

- characterized by the completion of mineralization - Before eruption, the surface of the crown is covered by the reduced enamel epithelium. This later degenerates as the tooth erupts into the mouth.

Question 33

What does the reduced enamel epithelium

Answer 33

1. the reduced ameloblasts that are in contact with the enamel, but are no longer able to undergo cell division 2. external cells = mostly stratum intermedium, undifferentiated epithelial cells able to divide and multiply, these external cells eventually = junctional epithelium

Question 34

What do pre ameloblasts induce

Answer 34

– the pre-ameloblasts induce cells of dental papilla to differentiate

Question 35

What do the odontoblasts differentiate from

Answer 35

from the mesenchyme of th dental papilla

Question 36

Give a brief description of the crown stage

Answer 36

1.Defined by beginning of mineralization. 2. Bell stage differentiation continues, away from cusp tips towards future cervical margin. 3. deposition of dentin followed by enamel

Question 37

What is the Hertwig's epithelial root sheath (HERS)

Answer 37

The Hertwig epithelial root sheath (HERS) or epithelial root sheath is a proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth

Question 38

Briefly describe the process of odontogenesis

Answer 38

1. Begins with induction of odontoblasts by ameloblasts. 2. Begins before amelogenesis. 3. Preodontoblasts secrete mantle dentine. 4. Odontoblasts grow long processes, which lengthen as dentine gets thicker. 5. Secretory phase: organic matrix laid down as predentine, which has lots of type 1 collagen. 6. Mineralisation phase

Question 39

Briefly describe amelogenesis

Answer 39

1. Ameloblasts differentiate, become elongated and deposit enamel matrix. 2. Initial enamel is aprismatic, but ameloblasts change shape resulting in prismatic enamel through most of crown. 3. Secretory phase: Organic matrix deposited and becomes mineralised almost instantly. 4. Maturation phase: hydroxyapatite crystals form and organic matrix largely removed.

Question 40

Describe what happens in the root stage

Answer 40

* After crown is complete, cervical margins (loop) of enamel organ grow down as root sheath (Hertwig’s root sheath). * Dental papilla cells differentiate into odontoblasts and deposit dentine. * Dental follicle cells differentiate into cementoblasts and fibroblasts to create cementum and periodontal ligament.

Question 41

What is the enamel organ derived from

Answer 41

The dental lamina proliferation

Question 42

What is the dental papilla and follicle derive from

Answer 42

Mesenchymal neural crest cells