Root Development (Lecture 3) Flashcards Preview

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Flashcards in Root Development (Lecture 3) Deck (22)
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1

Reduced Enamel Epithelium
• Remnant of _____.
• Formed by all four layers of the _____
• Combination of _____ and _____.
• Covers _____ crown.
• REE will fuse with _____ to form the junctional epithelium during tooth eruption.

enamel organ
enamel organ
protective ameloblasts
papillary layer
unerupted
oral epithelium

2

Root Dentinogenesis
• Events:

– REE grows in an apical direction at the _____.
– Becomes _____.
– Sheath formed by the joining of the _____ and _____.
– HERS induces _____ to become root odontoblasts.
– Root odontoblasts secrete _____ which is soon mineralized.
– HERS then detaches from root dentin and _____ – some remnants persist as _____.
– Roots are not complete until after the tooth has _____ and is in function.

cervical loop
hertwig's epithelial root sheath (HERS)
IEE
OEE
DP outer cells
circumpulpal predentin
disintegrates
epithelial rests of malassez
erupted

3

Root Formation
Hertwig’s Epithelial Root Sheath (HERS)

• Uniform growth of this sheath will result in the formation of a _____ rooted tooth
• Medial ingrowths or invaginations of this sheath will produce _____ rooted teeth
• The number of roots formed is determined by the number of _____ of the _____

single
multi
medial ingrowths
cervical loops

4

Root Formation
Hertwig’s Epithelial Root Sheath (HERS)
• Dentinogenesis.
– REE → _____ → Hertwig’s Epithelial Root Sheath (HERS).
– Epithelial diaphragm.
• Inner layer → induction of _____.
• Production of _____ and _____.

apical growth
root odontoblasts
root mantle
circumpulpal dentin

5

Root Formation
REE grows _____ → Hertwig’s Epithelial Root Sheath - HERS

Induction of DP cells to become _____, then _____

apically
root preodontoblasts
odontoblasts

6

Disintegration of HERS

Important to permit the invasion of _____

dental sac cells

7

Root Formation
• Dentinogenesis.
– Occurs at slower rate than _____.
• Multiple root formation.
– _____ of epithelial diaphragm.
– Multiple root sheaths or tunnels.
– Multiple root formation follows _____ of the epithelial diaphragm

coronal dentin
medial growth
unequal proliferation

8

Root Formation
• Cementogenesis.
– After first root dentin is deposited, the _____ of Herwig’s root sheath _____
• This new dentin comes in contact with _____ that have migrated from the dental sac
• This contact and signals from the odontoblasts induces the _____ to differentiate into _____, which then produce _____

cervical portion
breaks down
dental sac ectomesenchymal cells
dental sac ectomesenchymal cells
cementoblasts
cementum

9

Cementogenesis
– _____ migrate in and contact new root _____ surface.
– Induction of dental sac cells to differentiate into _____.
– Cementoblasts secrete organic matrix – _____ on new dentin surface.
– Cementoid mineralizes into _____.
– In the _____ 1⁄2 to 2/3 of the root, cementoblasts become entrapped in lacunae as _____.
• Similar arrangement as _____ in lacunae.

dental sac cells
dentin
cementoblasts
cementoid
cementum
apical
cementocytes
osteocytes

10

Root Formation
• Cementogenesis.
– Acellular extrinsic fiber cementum.
• _____ cementum.
• HERS _____.
• Source of cementoblasts:
– _____ induced by local factors.
– _____ transformation of HERS cells (less likely).

primary
disintegrates
dental sac ectomesenchyme cells
epithelial-mesenchymal

11

Root Formation
• Cementogenesis.
– Acellular extrinsic fiber cementum.
• _____deposition and intermingling with _____.
• Mineralizes _____ to _____.
• Slow development during eruption → cells remain on _____.
• No _____.

collagen fibril
mantle dentin fibrils
internal
external
surface
cementoid

12

Root Formation
• Cementogenesis.
– Cellular intrinsic fiber cementum.
• _____ cementum.
• Deposited after tooth is in _____.
• Deposited on _____ dentin surface – fiber intermingling.
• _____ formation w/less mineralization.
• Cementoblasts become entrapped in lacunae as _____.

secondary
occlusion
unmineralized
rapid
cementocytes

13

Periodontal Ligament
• Events:
– Dental sac ectomesenchyme cells differentiate into _____.
– Fibroblasts secrete _____.
– Collagen fibers become anchored in _____ as it is deposited by _____.

fibroblasts
collagen fibers
cementum
cementoblasts

14

Root Formation-Fate of HERS Cells
• Epithelial Rests of Malassez.
– Remnant of _____ that have _____ from the root surface.
– Network of _____ that remain within the PDL.
– Can become _____ within the PDL.
• Most will _____, while a few may calcify and become _____

HERS
detached
epithelial cells
tumor-forming cells
degenerate and disappear
'cementicles'

15

Root Anomalies
• Anomalies that result from a disturbance in _____.
– Exposed _____.
– Enamel _____.
– _____ canals.

hertwig's epithelial rooth sheath
root dentin
pearls
accessory root

16

Eruptive Tooth Movement
Reduced Enamel Epithelium (REE)

REE produces and releases _____ that degrade the tissues between _____ and _____

enzymes
REE
oral epithelium

17

Eruptive Tooth Movement
Fusion of tissues

REE fuses with _____
breakdown of _____

oral epithelium
oral epithelium

18

Eruptive Tooth Movement

Initial junctional epithelium
Tip of erupting tooth

The _____ of the tooth in the oral cavity
Formation of the _____

initial emergence
initial junctional epithelium

19

Eruptive Tooth Movement
• _____ continues to develop.
• _____ fibers develop.
• C.T. between reduced enamel epithelium (REE) and oral epithelium _____.
• REE and oral epithelium _____.
• Enzymes break down fused epithelia → _____ for eruption of crown.
• Following initial emergence of a tooth in oral cavity, its eruption _____ until it reaches the _____ plane.

alveolar process
PDL
degenerates
fuse
tunnel
speeds up (at maximum rate)
occlusal

20

Eruptive Tooth Movement
Dentogingival junction forms initially
from _____

REE

21

Eruptive Tooth Movement
- No _____, since the REE and oral epithelium have no _____ in them.
- The root formation of a tooth is _____ after the tooth has been in function:
• Deciduous teeth: _____ years. • Permanent teeth: _____years.

hemorrhage
blood vessels
not complete
1-1.5 years
2-3 years

22

Eruptive Tooth Movement
• Roots grow _____ → _____ resorbs.
• During eruption, _____ fill in resorbed fundus → _____.

apically
bony fundus
bony trabeculae
"bone ladder"