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Flashcards in Periodontium Deck (61):
1

What structures make up the periodontium?

Cementum
PDL
Bony socket
Gingiva facing the tooth

2

What are the two types of gingiva that face the tooth?

Junctional epithelium
Sulcular epithelium

3

What is the only perio structure not attached to the tooth

Sulcular epithelium

4

What immediately precedes periodontal development?

Root dentinogenesis

5

What is the coordination of periodontal development?

Cementoblasts and osteoblasts secrete their organic matrix
Then PDL fibroblasts secrete their organic matrix
Then the bone and cementum mineralize

6

How does the PDL develop during tooth eruption?

Collagen fiber bundles are added apically
The orientation of collagen fiber bundles change - they start obliquely, then horizontal, and then coronally oblique

7

How does the PDL develop after tooth eruption?

The thickness of collagen fiber bundles increase

8

What are the two types of cementum?

Primary Cementum
Secondary Cementum

9

Primary Cementum

Forms as the tooth is erupting
Mainly acellular
covers the coronal 2/3 of the tooth
Most important in attachment
More mineralized

10

Secondary Cementum

Formed after at least half the root is formed, around the time the tooth emerges in the oral cavity
Mainly cellular
Apical 2/3 of the root
Less mineralized
More important in adaptation

11

T/F - Primary and Secondary Cementum overlap in the middle 1/3 of the root

True - The Secondary cementum overlies the Primary

12

Why is cementum and dentin so firmly attached?

It is a consequence of the collagen fibers of the tissues intermingling between mineralization

13

As primary cementum is laid down, what happens to the cementoblasts?

They retreat towards the future PDL
They don't become entrapped in the cementum, but persist in the adult PDL

14

Epithelial Rests of Mallasez

Fragments of HERS that remain in the PDL

15

What is the main difference between primary and secondary cementogenesis?

In secondary cementogenesis, the cemntoblasts become trapped in cementum matrix - they're then called cementocytes

16

What does the sulcular epithelium derive from?

Embryonic oral epithelium

17

What does the junctional epithelium derive from?

Reduced enamel epithelium

18

Do cementoblasts derive from the dental follicle or the HERS?

We don't know - maybe both?

19

What is at the mineralization front of periodontal development?

Sialoprotein

20

Cementum

Hard connective tissue that covers the dentin of the root - similar to bone

21

How much of cementum is organic

45-55%
(90% collagen - mostly type I)

22

How much of cementum is inorganic?

50-55%

23

T/F - Cementum is secreted through life and not normally resorbed

True - Can triple in size from age 16-70

24

What are the functions of cementum

Attach tooth to the jaw
Protect the root dentin
Adapt to masticatory forces

25

How thick is the cementum in the CEJ v the apex of the root.

CEJ = thin (20-50um)
Apex = thicker (150-200um)

26

What are the types of joints at the CEJ?

Cementum overlaps enamel (60%)
Cementum buts up agains enamel (30%)
Gap between the cementum and enamel (10%)

27

Acellular extrinsic fiber cementum

Importance in attachment
Collagen fibers are at right angles to cementum surface
Has Sharpey's Fibers

28

Sharpey's Fibers

Fibers of the PDL that extend into the mineralized area

29

Cellular intrinsic cementum

Important in adaptation
Collagen fibers are parallel to the surface of cementum
Called intrinsic fibers because fibroblasts get caught in the cementum and are called cementocytes

30

Mixed fiber cementum

Some intrinsic, and some extrinsic
Make up most of the secondary cementum - made in the second wave of secondary cementum and found closer to the root apex

31

Cementocytes

Cementobalsts that got caught in the organic matrix
No longer make cementum - may be inactive

32

Periodontal ligament

Soft connective tissue between the cementum and the bony wall of the socket
Made up of large collagen fiber bundles with ends embedded in cementum/bone
Continuous with the gingival connective tissue cervically and apical foramen apically

33

How thick is the periodontal ligament?

.15-.40 mm (thin)
gets thinner with age

34

What cells are most numerous in the PDL?

Fibrobalsts

35

What do fibroblasts do in the PDL?

Secrete and degrade collagen
Cell-Cell junctions
Cell-ECM junctions

36

What non-fibroblasts cells are found in the PDL?

Cementoblasts
Osteoblasts/clasts
Epithelial rest of Mallasez
Immune cells
Stem cells

37

What is the collagen turnover in Gingiva v PDL?

Gingiva = 5 weeks
PDL = 1 week

38

What is the cell volume of Gingiva v. PDL?

Gingiva = 8%
PDL = 40%

39

What is the proliferation rates of Gingiva v. PDL?

Gingiva = lower
PDL = higher

40

What is the importance of Cell-ECM junctions

Functional link between occlusal forces and fibroblasts
Translate forces applied to fibroblast into physiological responses
Maintain orientation of fibroblasts in PDL

41

What is the structure of Cell-ECM junctions?

There are a variety of different junctions
They all interact with collagen in the ECM either by a single transmembrane molecule or several

42

Where are cementobalsts in the PDL?

Near cemetnum

43

Where are the osteoblsats and osteoclasts located in the PDL?

At the interface of the PDL and alveolar bone

44

Undifferentiated Mesenchymal Cell characeristics in the PDL

Perivascular location
Pluripotent

45

What types of fibers are in the ECM of the PDL?

Types I and III Collagen
Oxytalin

46

What is in the ground substance of ECM of PDL?

PGs and the associate GAGs
Glycoproteins

47

Cementicle

Spherical calcified mass in the PDL
Similar to pulp stones in the pulp

48

What are the principal fiber groups of the PDL?

Alveolar crest
Horizontal fibers
Oblique fibers
Apical fibers
Interradicular septum

49

Alevolar crest fibers

Attach cementum to the crest

50

Horizontal fibers

Attach cementum to the alveolar bone just below the crest

51

Oblique fibers

Attach cemntum to the alveolar bone in an oblique orientation that suspends the tooth in the socket

52

Apical fibers

Attach the apex of the tooth in the alveolar bone

53

Interradicular septum

Only found in teeth with multiple roots
Extend between the cementum and interredicular septum of alveolar bone

54

Gingival ligament

Important for maintaining the PDL and supporting the toth

55

Transseptal ligament

From cementum of tooth, arching over the alveolar bone, and attaching to the cementum of the adjacent tooth

56

T/F - The tooth is heavily vascularized

True

57

What are the 2 routes taken by blood vessels to supply the PDL?

1) Enter the alveolar bone and then pierce the foramina in the wall of the bony socket - via perforating arteries
2) Branch near the apical foramen and directly enter the PDL

58

What fibers signal pain in the PDL?

Small fibers
-A-delta
-C

59

What fibers signal proprioception in the PDL?

Large fibers
-A-beta

60

What are features of A-beta PDL fibers

Intermingle with collagen fibers
Highly sensitive
Code for the amount of force
Code for the direction of force
Send info to CNS regarding chewing
Underlie out ability to localize stimuli applied to teeth

61

Alveolar processes

Bone of jaw that contains sockets for teeth
Spongy bone