Early Tooth Development

Question 1

What are the 3 overlapping phases of tooth development?

Answer 1

1. Initiation
2. Morphogenesis
3. Histogenesis

Question 2

What 2 things occur during the initiation phase of odontogenesis?

Answer 2

1. Site of future teeth established

2. Appearance of tooth germ

Question 3

What occurs during the morphogenesis phase of odontogenesis?

Answer 3

Shape of teeth are determined by cell proliferation and movement

Question 4

What occurs during the histogenesis phase of odontogenesis?

Answer 4

Differentiation of cells give rise to all dental tissues

Question 5

At what age does tooth development begin?

Answer 5

6 weeks in utero

Question 6

Where are teeth derived from?

Answer 6

Ectoderm and mesoderm with contribution from neural crest cells

Question 7

What are neural crest cells?

Answer 7

Specialised group of migratory cells which originate from neuroectoderm

Question 8

What is the main function of NCCs?

Answer 8

Essential for the formation of most of the CT elements found in the head

Question 9

What is the stomodeum?

Answer 9

Primitive mouth lined by ectoderm

Question 10

What occurs in the initiation phase at 6 weeks in utero?

Answer 10

Oral epithelium of stomodeum thickens and invaginates to form primary epithelial band

Question 11

What is the primary epithelial band?

Answer 11

Horseshoe-shaped band which correspond roughly to shape of future dental arches

Question 12

What does the primary epithelial band divide into?

Answer 12

1. Vestibular lamina

2. Dental lamina

Question 13

What does the vestibular lamina go on to form?

Answer 13

Vestibule between cheek and tooth-bearing area

Question 14

What does the dental lamina contribute to the formation of?

Answer 14

Teeth

Question 15

What occurs at 8 weeks in utero during the morphogenesis stage of tooth development?

Answer 15

Dental lamina lengthens and forms swellings of epithelium surrounded by condensation of ectomesenchymal cells

Question 16

What do the epithelial swelling and ectomesenchymal cells make up?

Answer 16

Tooth germs

Question 17

What are the 3 stages that tooth germs can be classified into?

Answer 17

1. Bud stage
2. Cap stage
3. Bell stage

Question 18

What occurs during the bud stage?

Answer 18

Extensive proliferation of dental lamina into buds

Question 19

What is the term given to the tooth germ once the bud stage occurs?

Answer 19

Enamel organ

Question 20

How many buds will be present in each arch?

Answer 20

10

Question 21

What 2 main things occur during the cap stage?

Answer 21

1. Proliferation of the cells of the enamel organ

2. Deeper surface of enamel organ invaginates

Question 22

What 4 major structures are present in the cap stage?

Answer 22

1. Enamel organ
2. Dental papilla
3. Dental sac
4. Stella reticulum

Question 23

What is the enamel organ?

Answer 23

Formation of tooth bud In a cap shape with a deep central impression

Question 24

What is the dental papilla?

Answer 24

Condensed mass of ectomesenchyme within the concavity of the enamel organ

Question 25

What is the dental sac?

Answer 25

Condensed mass of ectomesenchyme surrounding the outside of the enamel organ

Question 26

What is the stellate reticulum?

Answer 26

Cells in the centre of the enamel organ which have separated and accumulated GAGs in between

Question 27

What 2 things occur during the early bell stage?

Answer 27

1. Dental lamina breaks down and enamel organ loses contact with oral epithelium 2. Dental lamina between tooth germs degenerate

Question 28

What are the two types of tissues in the dental papilla during the early bell stage?

Answer 28

1. Odontoblasts | 2. Primordium of the pulp

Question 29

What occurs during the late bell stage?

Answer 29

Apposition stage - Formation of hard dental tissues

Question 30

How do ameloblasts arise?

Answer 30

Internal enamel epithelium lines along basement membrane and differentiates into preameloblasts which in turn differentiate into ameloblasts

Question 31

How do odontoblasts arise?

Answer 31

Outer cells of dental papilla differentiate into odontoblasts

Question 32

What are the 6 main bell stage structures?

Answer 32

1. Dental follicle 2. External enamel epithelium 3. Stellate reticulum 4. Stratum intermedium 5. Internal enamel epithelium 6. Dental papilla

Question 33

At what stage do small blood vessels invade the dental papilla?

Answer 33

Early bell stage

Question 34

At what stage do nerve fibres form a plexus below the dental papilla?

Answer 34

Cap stage