Odontogenesis

Question 1

what happens during initiation?

Answer 1

underlying ectomesenchymal cell induce the overlying ectoderm (oval epithelium) to proliferate, forming a localized thickening at the site of each tooth celled the dental lamina

Question 2

when does initiation occur?

Answer 2

starts at 6 weeks in utero

Question 3

when does the bud stage occur?

Answer 3

starts at 8 weeks in utero

Question 4

what happens during the cap stage?

Answer 4

the enamel organ begins to form, which is composed of a single layer of cells at the convex region (outer enamel epithelium, OEE) and the concave region (inner enamel epithelium, IEE). Between the two epithelial layers is loosely arranged stellate reticulum. Some cells of the stellate reticulum become densely packed near the IEE and are known as the enamel knot. The dental papilla is composed of condensed ectomesenchymal cells located within the concavity of the enamel organ. The dental follicle (dental sac) is the capsule-like encasing of mesenchyme surrounding the enamel organ.

Question 5

tooth germ

Answer 5

enamel organ, dental papilla, dental follicle

Question 6

when does the bell stage happen?

Answer 6

it starts at week 11 in utero

Question 7

what happens during the bell stage?

Answer 7

morphodifferentiation and histodifferentiation of specific cells. the enamel organ is now well-defined and composed of the following: OEE (outermost layer of the enamel organ), IEE (innermost layer of the enamel organ), stratum intermedium (forms directly lateral to the IEE), stellate reticulum (becomes more sparsely arranged due to increased proteoglycan synthesis). the enamel knot disappear. The cells in the IEE become tall and columnar (now called preameloblasts) first. The cells of the dental papilla closest to the IEE become tall and columnar (now called preodontoblasts) after the preameloblasts are formed. The dental lamina disintegrates.

Question 8

When does the appositional stage start?

Answer 8

At week 14 in utero

Question 9

What happens during the appositional stage?

Answer 9

the reduced enamel epithelium (REE) forms when the stellate reticulum collapses, merging OEE with IEE. Odontoblasts secrete dentin matrix first. Ameloblasts secrete enamel matrix after dentin is first formed. Root formation begins. The dental papilla forms the pulp tissue. The dental follicle forms cementum, alveolar bone, and PDL.

Question 10

what happens during root formation?

Answer 10

Begins at the cervical loop (where the OEE and IEE join) after enamel is first formed. As the cervical loop elongates, HERS is formed, which shapes the roots and ultimately surrounds the majority of the dental papilla. As radicular dentin is formed HERS begins to disintegrate, leaving behind patches of epithelial cells called epithelial rests of Malassez. The collapse of HERS enables ectomesenchymal cells of dental follicle to contact dentin and differentiate into the formative cells of periodontium: cementoblasts, osteoblasts, and fibroblasts.

Question 11

When does the cap stage occur?

Answer 11

It starts at week 9 in utero.

Question 12

What happens during eruption?

Answer 12

As the tooth erupts into the oral cavity, the reduced enamel epithelium (REE) fuses with the oral epithelium, forming the dentogingival junction (epithelial attachment). This later migrates apically along the tooth into its normal position in which the most apical cells of the JE are at the CEJ. A delay in the apical migration is known as delayed (altered) passive eruption.

Question 13

What is the chronological order of enamel and dentin formation?

Answer 13

1. differentiation of ameloblasts.
2. differentiation of odontoblasts.
3. deposition of dentin matrix.
4. deposition of enamel matrix.

Question 14

what happens after IEE cells differentiate into preameloblasts?

Answer 14

differentiation of preodontoblasts from mesenchymal cells of the dental papilla

Question 15

What disintegrates following tooth formation?

Answer 15

dental lamina
ameloblasts
HERS
reduced enamel ep.

Question 16

What is the precursor for ameloblasts?

Answer 16

inner enamel ep.

Question 17

what is the precursor for HERS?

Answer 17

outer enamel ep.

Question 18

What is the precursor for reduced enamel ep?

Answer 18

IEE, OEE, stratum intermedium, stellate reticulum

Question 19

What is the precursor for junctional ep?

Answer 19

reduced enamel ep.

Question 20

What is the precursor for root formation?

Answer 20

HERS

Question 21

what is the precursor for pulp?

Answer 21

dental papilla

Question 22

what is the precursor for dentin

Answer 22

dental papilla

Question 23

what is the precursor for alveolar bone?

Answer 23

osteoclasts

Question 24

what is the precursor for cementum?

Answer 24

cementoblasts

Question 25

what is the precursor for the periodontal ligament

Answer 25

fibroblasts

Question 26

What does the dental sac differentiate into?

Answer 26

cementoblasts fibroblasts osteoclasts

Question 27

what is the precursor for dental sac and dental papilla?

Answer 27

ectomesenchyme

Question 28

what forms the dental lamina?

Answer 28

oral epithelium

Question 29

original precursor cells of enamel

Answer 29

epithelial cells

Question 30

original precursor cells of dentin, pulp, cementum

Answer 30

ectomesenchymal cells

Question 31

ectoderm

Answer 31

tissues covering the outside of the body / epidermis, hair, nails, etc

Question 32

mesoderm

Answer 32

connective tissues / heart, muscle, blood cells, bone, dermis, etc

Question 33

endoderm

Answer 33

tissues lining inside the body / lung, stomach, intestine, liver, etc

Question 34

what forms from the neural crest

Answer 34

sensory ganglia connective tissues of head and neck (bone, cartilage, muscles, tooth, etc)

Question 35

enamel organ

Answer 35

(aka dental organ) proliferation of epithelial cells

Question 36

dental papilla

Answer 36

condensation of ectomesenchymal cells

Question 37

dental sac

Answer 37

(aka dental follicle) capsule like condesation of ectomesenchymal cells

Question 38

future tooth product of enamel organ

Answer 38

enamel

Question 39

future tooth product of dental papilla

Answer 39

dentin | pulp

Question 40

future tooth product of dental sac

Answer 40

cementum periodontal ligament alveolar bone connective tissues of gingiva

Question 41

tooth germ

Answer 41

enamel organ + dental papilla + dental follicle

Question 42

purpose of inner enamel ep

Answer 42

generates enamel

Question 43

purpose of the cervical loop

Answer 43

root formation

Question 44

purpose of the stella reticulum

Answer 44

protect inner enamel ep.

Question 45

purpose of enamel knot

Answer 45

location of cusp

Question 46

when are the enamel knot, enamel cord, and enamel navel present

Answer 46

during the cap stage

Question 47

differentiation of ameloblasts

Answer 47

older, taller polarized (cusp tip) | younger, shorter, unpolarized (root)

Question 48

dentin =

Answer 48

collagen + hydroxyapaptite crystals

Question 49

enamel =

Answer 49

amelogenin +hydroxapatite crystals

Question 50

amelogenin

Answer 50

resorbable --> allows further packing of crystals --> inorganic component, hardness

Question 51

promote calcificaiton

Answer 51

``` alkaline phosphatase (supply phosphate) pyrophosphatase (hydrolyze phosphate) ```

Question 52

inhibit calcification

Answer 52

pyrophosphate

Question 53

matrix vesicles

Answer 53

contain essential components contain seed of crystal released from odontoblasts to collagen matrix

Question 54

what reverses calcification

Answer 54

acid

Question 55

sharpey's fiber

Answer 55

collagen fibers of periodontal ligament embedded in cementum

Question 56

cementoblasts

Answer 56

secrete cementoid (matrix) and mineralize cementum on root dentin

Question 57

enervation in cap stage

Answer 57

axons enter the dental follicle

Question 58

enervation in bell stage

Answer 58

axons enter dental papilla following the initiation of dentinogenesis

Question 59

remnants of odontogenic epithelial cells

Answer 59

epithelial rests of Malassez remnant of HERS located in periodontal ligament

Question 60

hardest tissue found in the oral cavity

Answer 60

enamel

Question 61

the dental lamina

Answer 61

is derived from ectoderm

Question 62

collagen is not the major component of matrix of

Answer 62

enamel

Question 63

what is present in bell stage

Answer 63

OEE, IEE, stellate reticulum, stellate intermedium

Question 64

cementogenesis starts prior to

Answer 64

formation of apical foramen

Question 65

odontoblasts are characterized by

Answer 65

possessing long cytoplasmic processes which lie within dentinal tubules

Question 66

pulp chamber of a mature tooth contains

Answer 66

blood vessels and nerves