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Oral Histology > Periodontium > Flashcards

Periodontium Flashcards

1
Q

What structures make up the periodontium?

A

Cementum
PDL
Bony socket
Gingiva facing the tooth

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2
Q

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

A

Junctional epithelium

Sulcular epithelium

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3
Q

What is the only perio structure not attached to the tooth

A

Sulcular epithelium

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4
Q

What immediately precedes periodontal development?

A

Root dentinogenesis

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5
Q

What is the coordination of periodontal development?

A

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

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6
Q

How does the PDL develop during tooth eruption?

A

Collagen fiber bundles are added apically

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

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7
Q

How does the PDL develop after tooth eruption?

A

The thickness of collagen fiber bundles increase

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8
Q

What are the two types of cementum?

A

Primary Cementum

Secondary Cementum

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9
Q

Primary Cementum

A 
Forms as the tooth is erupting
Mainly acellular
covers the coronal 2/3 of the tooth
Most important in attachment
More mineralized
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10
Q

Secondary Cementum

A 
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
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11
Q

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

A

True - The Secondary cementum overlies the Primary

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12
Q

Why is cementum and dentin so firmly attached?

A

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

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13
Q

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

A

They retreat towards the future PDL

They don’t become entrapped in the cementum, but persist in the adult PDL

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14
Q

Epithelial Rests of Mallasez

A

Fragments of HERS that remain in the PDL

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15
Q

What is the main difference between primary and secondary cementogenesis?

A

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

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16
Q

What does the sulcular epithelium derive from?

A

Embryonic oral epithelium

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17
Q

What does the junctional epithelium derive from?

A

Reduced enamel epithelium

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18
Q

Do cementoblasts derive from the dental follicle or the HERS?

A

We don’t know - maybe both?

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19
Q

What is at the mineralization front of periodontal development?

A

Sialoprotein

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20
Q

Cementum

A

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

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21
Q

How much of cementum is organic

A

45-55%

90% collagen - mostly type I

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22
Q

How much of cementum is inorganic?

A

50-55%

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23
Q

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

A

True - Can triple in size from age 16-70

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24
Q

What are the functions of cementum

A

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

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25
Q

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

A 
CEJ = thin (20-50um)
Apex = thicker (150-200um)
26
Q

What are the types of joints at the CEJ?

A

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

27
Q

Acellular extrinsic fiber cementum

A

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

28
Q

Sharpey’s Fibers

A

Fibers of the PDL that extend into the mineralized area

29
Q

Cellular intrinsic cementum

A

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
Q

Mixed fiber cementum

A

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
Q

Cementocytes

A

Cementobalsts that got caught in the organic matrix

No longer make cementum - may be inactive

32
Q

Periodontal ligament

A

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
Q

How thick is the periodontal ligament?

A

.15-.40 mm (thin)

gets thinner with age

34
Q

What cells are most numerous in the PDL?

A

Fibrobalsts

35
Q

What do fibroblasts do in the PDL?

A

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

36
Q

What non-fibroblasts cells are found in the PDL?

A 
Cementoblasts
Osteoblasts/clasts
Epithelial rest of Mallasez
Immune cells
Stem cells
37
Q

What is the collagen turnover in Gingiva v PDL?

A 
Gingiva = 5 weeks
PDL = 1 week
38
Q

What is the cell volume of Gingiva v. PDL?

A 
Gingiva = 8%
PDL = 40%
39
Q

What is the proliferation rates of Gingiva v. PDL?

A 
Gingiva = lower
PDL = higher
40
Q

What is the importance of Cell-ECM junctions

A

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

41
Q

What is the structure of Cell-ECM junctions?

A

There are a variety of different junctions

They all interact with collagen in the ECM either by a single transmembrane molecule or several

42
Q

Where are cementobalsts in the PDL?

A

Near cemetnum

43
Q

Where are the osteoblsats and osteoclasts located in the PDL?

A

At the interface of the PDL and alveolar bone

44
Q

Undifferentiated Mesenchymal Cell characeristics in the PDL

A

Perivascular location

Pluripotent

45
Q

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

A

Types I and III Collagen

Oxytalin

46
Q

What is in the ground substance of ECM of PDL?

A

PGs and the associate GAGs

Glycoproteins

47
Q

Cementicle

A

Spherical calcified mass in the PDL

Similar to pulp stones in the pulp

48
Q

What are the principal fiber groups of the PDL?

A 
Alveolar crest
Horizontal fibers
Oblique fibers
Apical fibers
Interradicular septum
49
Q

Alevolar crest fibers

A

Attach cementum to the crest

50
Q

Horizontal fibers

A

Attach cementum to the alveolar bone just below the crest

51
Q

Oblique fibers

A

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

52
Q

Apical fibers

A

Attach the apex of the tooth in the alveolar bone

53
Q

Interradicular septum

A

Only found in teeth with multiple roots

Extend between the cementum and interredicular septum of alveolar bone

54
Q

Gingival ligament

A

Important for maintaining the PDL and supporting the toth

55
Q

Transseptal ligament

A

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

56
Q

T/F - The tooth is heavily vascularized

A

True

57
Q

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

A

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
Q

What fibers signal pain in the PDL?

A

Small fibers

  • A-delta
  • C
59
Q

What fibers signal proprioception in the PDL?

A

Large fibers

-A-beta

60
Q

What are features of A-beta PDL fibers

A 
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
Q

Alveolar processes

A

Bone of jaw that contains sockets for teeth

Spongy bone

Oral Histology (12 decks)

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