Chapter 21

Question 1

When does root formation begin?

Answer 1

Begins after the outline of the crown has been established but before the full crown is calcified

Question 2

Layers of OEE and IEE make up what?

Answer 2

Epithelial root sheath (Hertwig’s epithelial root sheath)

Question 3

Epithelial root sheath (Hertwig’s epithelial root sheath)

Answer 3

Begin to undergo rapid miotic division and grow deep into the underlying connectice tissues - The beginning of root formation

Question 4

Dentinocemental junction

Answer 4

Some epithelial root sheath cells do not pull away and may become ameloblasts, forming small globes of enamel on the surface of the dentin

Question 5

Enamel pearls

Answer 5

Found in bifurcations and trifurcations of roots

Question 6

A hard, yellowish substance covering the root of the tooth

Answer 6

Cementum

Question 7

% of inorganic hydroxypatite crystals in cementum

Answer 7

45% to 50%

Question 8

% of organic components of water in cementum

Answer 8

50% to 55%

Question 9

CEJ

Answer 9

First seen at the cervical line of the tooth, also called the cementoenamel

Question 10

How many different relationships with the enamel of the crown

Answer 10

3

Question 11

60% of the cases of cementum

Answer 11

overlaps the enamel

Question 12

30% the cementum meets

Answer 12

the enamel at a sharp junctions

Question 13

10% of the cases the cementum

Answer 13

and enamel do not meet, leaving dentin exposed at the cervical line

Question 14

Acellular cementum

Answer 14

All of the cementoblasts remain on the surface rather than becoming trapped within the cementum

Question 15

Where is acellular

Answer 15

In the cervical two thirds of the root

Question 16

Cellular cementum

Answer 16

More vital than acellular cementum and therefore more responsive to remodeling itself

Question 17

Where is cellular cementum

Answer 17

Apical 1/3 of the root

Question 18

The cellular at the apex of the root tends to

Answer 18

inrease in thickness with the passage of time and as a result of stress causing thickening (hypercementosis)

Question 19

Makes extraction a bit more difficult than usual

Answer 19

Hypercementosis

Question 20

Periodontal membrane (ligament)

Answer 20

Forms the middle of the layer of cells in the old dental sac, the ends of the periodontal fibers become surrounded by cementoblasts, whose secretion hardens around the ends of the fibers, attaching them to the cementum

Question 21

Parts of the periodontal ligament embedded in cementum are known as

Answer 21

Sharpey’s fibers

Question 22

Sharpey’s fibers (SF)

Answer 22

Parts of the PDL surrounded by cementum on the tooth side and alveolar bone on the opposite side in the wall of the tooth socket

Question 23

Alveolar bone

Answer 23

Is the bone of the upper or lower jaw that makes up the sockets for the teeth

Question 24

3 layers of alveolar bone

Answer 24

Cortical plate
Cribiform plate or alveolar bone proper
Spongy or cancellous bone

Question 25

First layer of alveolar bone

Answer 25

Layer of compact bone on the buccal or lingual surface is referred to as the cortical plate of bone.

Question 26

Second layer of alveolar bone

Answer 26

Called the cribriform plate or alveolar bone proper. Radiographically it is referred to as the lamina dura

Question 27

Bundle bone

Answer 27

The tooth socket is constantly being remodeled and additional bone laid down on the cribriform plate

Question 28

A thickened lamina dura is caused by

Answer 28

bundle bone being laid down on the cribriform plate and is an indication of occlusal trauma to that tooth or teeth

Question 29

Between the coritcal plate and cribriform plate

Answer 29

Layer of spongy or cancellous bone (3rd layer)

Question 30

Spongy bone is a

Answer 30

bone marrow

Question 31

Interproximal alveolar crest

Answer 31

The spongy bone and the crest of bone that joins two sockets

Question 32

Three groups of the periodontal ligament

Answer 32

Gingival fibers, transseptal fibers, and alveolodental fibers

Question 33

After a person has had a root canal on a tooth, it is still possible to feel pain at times from the

Answer 33

periodontal ligament

Question 34

Gingival fibers

Answer 34

Run from the cementum into the free and attached gingival area; support the gingiva

Question 35

Circular gingival fibers

Answer 35

run around the tooth in free gingiva and hold gingiva against the tooth

Question 36

Transseptal fibers

Answer 36

Run from the cementum of the interproximal portion of one tooth, across the alveolar crest of bone, to the cementum of the interproximal portion of the adjacent tooth; hold the teeth in interproximal contact

Question 37

Alveolodental fibers

Answer 37

Run from cementum to alveolar bone

Question 38

what are the alveolodental fiber groups

Answer 38

``` Alveolar crest group Horizontal group Oblique group Apical group Interradicular group ```

Question 39

Alveolar crest group

Answer 39

Runs from cementum, slightly apical to the alveolar crest of bone; helps resist horizontal movements of teeth

Question 40

Horizontal group

Answer 40

Runs from cementum horizontally to the alveolar crest; helps resist horizontal movement

Question 41

Oblique group

Answer 41

runs from cementum cornily into the alveolar bone; main fiber group for resisting occlusal stresses

Question 42

Apical group

Answer 42

Runs from apex of the tooth into the adjacent alveolar bone; resists forces trying to pull the tooth from its socket

Question 43

Interradicular group

Answer 43

Found only on multirooted teeth; runs from the alveolar crest of the bone between the roots of the tooth to adjacent cementum; resists the forces trying to remove the tooth

Question 44

What happens when a tooth is lost

Answer 44

The posterior to the missing tooth will tilt forward into the unoccupied space (mesial drift)

Question 45

If a tooth if moved too fast in orthodontic treatment

Answer 45

It is possible that the fibers attaching the tooth to bone will be torn out of their attachment; Before they can be re-embedded, the tooth could conceivably loosen and be lost or could cause external root resorption