Tooth Development

Question 1

What represents the beginning of odontogenesis?

Answer 1

The appearance of dental lamina arising from the oral epithelium

Question 2

Adontia, stage?

Answer 2

Congenital absence of ALL teeth
Associated with Ectodermal Dysplasia
During initiation

Question 3

Partial Adontia, Stage?

Answer 3

Hypodontia (1-5 teeth missing)
Oligodontia (>6 teeth missing)
Developmental disturbance with dental lamina formation
No tooth germs
Max latereal incisors are the most common to be missing
During initiation

Question 4

Hyperdontia (Polydontia), stage?

Answer 4

Extra teeth
permamnent dentition
Mesiodens, common example
Extra tooth germ is formed
During Initiation

Question 5

Primary Epithelial band formation

Answer 5

Thickened epithelium (ectoderm) in place of future jaws
Rapid cell division gives rise to 2 subdivisions dental lamina and vestibular lamina

Question 6

Bud Stage

Answer 6

Oral epithelium invaginates into the ectomesenchyme which will condensate

Question 7

What does dental lamina rise from?

Answer 7

Ectoderm lining of stomadeum –> oral epithelium –> dental lamina

Question 8

What influences the ectomesenchyme?

Answer 8

Neural crest cells

Question 9

Lateral lamina

Answer 9

Tethers the bud of dental lamina

Question 10

Cap stage

Answer 10

Epithelial outgrowth of enamel orga forms cap over ectomesenchyme
Bud–> Enamel organ
Ectomesenchyme–>Dental Papilla
Dental follicle surrounds the enamel organ and dental papilla
Inner enamel epithelium become ameloblasts

Question 11

Degeneration of the vestibular lamina gives rise to what structures
(Cap stage)

Answer 11

Epithelial lining for 
Oral vestibule
Alveolar mucosa
Parts of gingival mucosa
Inner lip mucosa
Mucosal space btw the cheeks or lips

Question 12

Dens in dente, what stage?

Answer 12

Tooth within a tooth
Enamel organ expands more than it should and invaginates into the dental papilla
During cap stage

Question 13

Fusion, stage?

Answer 13

Union of 2 teeth by dentin and enamel
Fewer number of teeth
Extra wide crown with 1 pulp cavity
During Cap stage

Question 14

Gemination, stage?

Answer 14

1 tooth attempting to divide, abnormally wide crown, incomplete
Correct number of teeth
During Cap stage

Question 15

Bell Stage General

Answer 15

Deepening of the undersurface
Morphodifferentiation
Histodifferentiation
Dental lamina disintegrates

Question 16

Morphodifferentiation

Answer 16

Occurs during Bell stage

Enamel organ takes on the shape of an incisor, canine, or molar

Question 17

Histodifferentiation

Answer 17

During bell stage

Ameloblasts (enamel) and odontoblasts (dentin) acquire their phenotype

Question 18

Tooth germ consists of

Answer 18

Enamle organ, dental lamina, dental papilla

Question 19

Bell Stage In depth

Answer 19

Dental lamina disintegrates
Tooth continues to develop separate from the oral epithelium
Crown pattern established
Stellate reticulum thin over cusp tip
Stratum intermedium assists ameloblasts and nourishes them

Question 20

Early Bell Stage

Answer 20

Histodifferentiated enamel organ (cervical loop region) is supported by basal lamina around periphery

Question 21

Development of Succedaneous Teeth

Answer 21

Proceed through all the same stages of odontogenesis as primary teeth do

Question 22

Permanent Molar development

Answer 22

Posteriormost extent of dental lamina does not disintegrate, elongates in a posterior direction giving rise to 12 buds –> permanent molars

Question 23

Incisors, canines, and premolar development

Answer 23

Form due to further proliferative activity within the dental lamina
On lingual aspect of deciduous tooth germ

Question 24

Dental Papilla cells

Answer 24

Peripheral cells of papilla face Inner enamel epithelium and differentiate into odontoblasts which secrete dentin
Inner cells of dental papilla form pulp

Question 25

Dental Follicle Cells

Answer 25

Inner cells closest to the enamle organ become cementocytes and form cementum Outer cells form PDL and contribute to alveolar bone formation

Question 26

Which 2 cells help in formation of enamel?

Answer 26

Stratum intermedium and Inner enamel epithelium

Question 27

Cervical Loop region/Zone of Flexion of the Enamel Organ

Answer 27

Hertwigs Epithelial Rooth Sheath (HERS) joining of IEE and OEE Initiates root formation Gives rise to epithelial component of root after crown is formed

Question 28

Cervical Loop cont.

Answer 28

``` Rapid cell division within cervical loop Enamel organ elongates Depth of the concavity increases and enamel organ resembles bell Crown joins the root Enamel joins the cementum ```

Question 29

Crown pattern Development

Answer 29

Pattern and number of cusps is establishedby complete folding of the IEE (morphodifferentiation)

Question 30

What causes folding of IEE?

Answer 30

Intrinsic growth caused by differential rates of mitotic division within the IEE Stellate reticulum over cusp tips is reduced

Question 31

Epithelial Pearls or Rests of Serres

Answer 31

Fragmentation of dental lamina results in discrete clusters of epithelial cells surrounded by connective tissue and normally degenerate Some are phagocytosed If they persist they are deemed Epi Pearls/ Rests of Serres

Question 32

What could Epithelial Pearls form?

Answer 32

Eruption cysts- cells form over developing tooth and delay eruption Odontomes, or activated to form supernumerary teeth

Question 33

Cusp Development

Answer 33

Growth center- point at which IEE cell differentiation first occurs --> site of future cusp development A 2nd xone of differentiation within IEE leads to second cusp and so on

Question 34

Enamel Knot (Ahrens Knot)

Answer 34

Embryonic signaling center- provides positional info for tooth morphogenesis Ectomesenchymal cells of papilla induce cells of knot to express signaling molecules Know cells control folding of IEE (cuspal morpho) Incisors have 1 know Molars have multiple Knots undergo apoptosis

Question 35

Enamel Cord

Answer 35

Associated with the placement of the 1st cusp | Also called enamel septum

Question 36

Microdontia, stage?

Answer 36

Small teeth Max incisors and 3rd molars often affected Peg lateral During Bell stage

Question 37

Macrodontia, stage?

Answer 37

Large teeth | Uncommon, associated with Hemifacial Hypertrophy

Question 38

Amelogenesis Imperfecta, stage?

Answer 38

Hereditary, enamel formation disorder

Question 39

Dentinogenesis Imperfecta

Answer 39

Hereditary affects dentin | Clear yellow grey teeth