Exam 2 10/16 Intro to Tooth Development

Question 1

Teeth make up ____ of the surface area of the mouth

Answer 1

20% (upper a little more than the lower arch)

Question 2

Functions of teeth

Answer 2

• mastication
• speech
• esthetics
• weapons of attack and defense

Question 3

What makes up a tooth?

Answer 3

• enamel
• dentin
• pulp
• periodontium (cementum, periodontal ligament, alveolar bone)

Question 4

____ is soft connective tissue

Answer 4

Pulp

Question 5

What is the difference between anatomical and clinical cervix?

Answer 5

Depends on where the gingiva ends - if it ends at the cervical margin, anatomical = clinical cervix. If it ends higher, clinical cervix is longer than the anatomical cervix

Question 6

When do hard tissues get deposited in the developing teeth?

Answer 6

11-12 weeks

Question 7

Initial signs of tooth development is at __ weeks

Answer 7

6

Question 8

How long does tooth development take?

Answer 8

18-25 years (considering wisdom teeth that are the last ones to erupt)

Question 9

Enamel is derived from:

Answer 9

Oral ectoderm/epithelium

Question 10

What structures of a tooth are derived from ectomesenchyme?

Answer 10

• dentin
• pulp
• cementum
• periodontal ligament
• portion of alveolar bone

Question 11

What structures arise from the dental papilla?

Answer 11

Dentin, pulp

Question 12

What structures arise from the dental follicle/sac?

Answer 12

• cementum
• periodontal ligament
• portion of alveolar bone

Question 13

The earliest histological indication of tooth development is at:

Answer 13

11 days (thickening of oral epithelium where tooth formation will occur on the oral surface of the first pharyngeal arch)

Question 14

____ is essential for the initiation of tooth development; maintained by _____

Answer 14

First arch epithelium; cells of dental papilla

Question 15

What happens to the primary epithelial band?

Answer 15

Thickens as a result of different planes of cell division and grows into the underlying ectomesenchyme - leads to formation of dental lamina and vestibular lamina

Question 16

As the primary epithelial band thickens, what happens to the surrounding ectomesenchyme?

Answer 16

Condenses around area of dental lamina; tooth bud continues to grow and reshape in relation to the ectomesenchyme condensing around it

Question 17

Where does the vestibular lamina form in relation to the dental lamina?

Answer 17

Buccal

Question 18

What eventually happens to the vestibular lamina?

Answer 18

Eventually degenerates so that there is no connection between lip and alveolar process (so vestibules form properly)

Question 19

When does the primary epithelial band form?

Answer 19

Around 37 days

Question 20

How many dental laminas form in total?

Answer 20

10 in each arch (20 primary teeth)

Question 21

Where is the basement membrane found in the tooth bud?

Answer 21

Between ectomesenchyme and oral epithelium (around the round part of the bud)

Question 22

Where does permanent dentition arise from?

Answer 22

Dental lamina; Permanent molars are an exception, as they are derived from the backgrowth of the primary epithelial band

Question 23

Stages of tooth development (8)

Answer 23

1. Bud
2. Cap
3. Bell
4. Early Crown Dentinogenesis
   E. Crown amelogenesis
   F. Late crown formation
   G. Root formation and eruption
   H. Function

Question 24

____ is always produced before ____ during crown formation

Answer 24

Dentin always produced before enamel

Question 25

Which stage of tooth development is most complex histologically?

Answer 25

Bell

Question 26

First epithelial incursion into ectomesenchyme of the jaw occurs during:

Answer 26

Bud stage

Question 27

What components make up bud?

Answer 27

Dental lamina (poking finger), oral epithelium towards the top

Question 28

What happens during cap stage?

Answer 28

proliferation of epithelium, ectomesenchyme condensation increases around the cap (enamel organ)

Question 29

Successional dental lamina can be found beginning at which stage of tooth development?

Answer 29

Cap stage

Question 30

What components can be found during cap stage?

Answer 30

Enamel organ, Dental Papilla, Dental follicle, cervical loops

Question 31

Enamel of tooth is derived from:

Answer 31

Enamel organ

Question 32

Dental papilla forms:

Answer 32

dentin and pulp

Question 33

Dental follicle forms:

Answer 33

cementum, periodontal ligament, part of alveolus

Question 34

What cells sit on top of dental papilla

Answer 34

Inner enamel epithelium

Question 35

Cells on periphery of ectomesenchyme =

Answer 35

outer enamel epithelium

Question 36

Cervical loops

Answer 36

Where inner and outer enamel epithelium meet (where HERS roots come from)

Question 37

Where is stratum intermedium found

Answer 37

Along the inner enamel epithelium

Question 38

Enamel organ is filled with what cells

Answer 38

Stellate reticulum

Question 39

What do stratum intermedium do

Answer 39

Regulating transport of ions to ameloblasts so they can secrete the enamel

Question 40

Main change that occurs during Bell stage

Answer 40

Change in shape of crown; completed differentiation of the enamel organ

Question 41

Dense condensation inside enamel organ:

Answer 41

Enamel knot

Question 42

When does dental lamina begin to degenerate?

Answer 42

Autolysis after enamel organ is differentiated

Question 43

Bell stage is marked by:

Answer 43

histodifferentiation and morphodifferentiation

Question 44

Basement membrane becomes:

Answer 44

DEJ

Question 45

___ is a potential space

Answer 45

DEJ (caries can spread out here)

Question 46

If dental lamina cells persist, what happens?

Answer 46

General cell islands may persist, may form small eruption cysts that delay eruption of the tooth

Question 47

Internal dental epithelium folds, making it possible to:

Answer 47

Recognize shape of future crown pattern

Question 48

Enamel knot is often continuous with:

Answer 48

Enamel cord or septum

Question 49

What does enamel knot represent

Answer 49

Organizational center that orchestrates cuspal morphogenesis

Question 50

As calcification occurs, the dental papilla becomes:

Answer 50

Dental pulp

Question 51

Tooth bone socket develops around tooth via:

Answer 51

Intramembranous bone formation

Question 52

Presence of _____ induces lining up and differentiation of ectomesenchyme along the basement membrane and become odontoblasts

Answer 52

Inner enamel epithelium

Question 53

Formation of dentin marks the onset of:

Answer 53

Crown stage

Question 54

Mineralization of dentin induces differentiation of internal dental epithelium into:

Answer 54

Ameloblasts (secrete enamel)

Question 55

Mineralization begins at _____ and proceeds ____

Answer 55

incisal/cuspal tip; coronally (toward cervix)

Question 56

True or false: odontoblasts secrete mineralized dentin

Answer 56

False - they secrete the organic matrix which mineralizes as an extracellular event

Question 57

Root formation happens from what part of tooth germ?

Answer 57

Cervical loops

Question 58

WHat happens during root formation?

Answer 58

Epithelial cells proliferate from cervical loop of enamel organ to form a double layer of cells (HERS)

Question 59

HERS extends around:

Answer 59

Dental pulp/between it and dental follicle

Question 60

True or false: HERS completely surrounds dental pulp

Answer 60

False - all but basal portion of pulp --> primary apical foramen

Question 61

When root sheath is enclosing more of expanding dental pulp, what happens to the ectomesenchymal cells facing the pulp?

Answer 61

Induces them to differentiatiate into odontoblasts and produce dentin of the root