(6) Cementum Flashcards

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1
Q

Is precemnetum calcified or uncalcified?

A

Uncalcified

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2
Q

Is cementum more or less hard than dentin and enamel?

A

Softer than

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3
Q

Is cementum more permeable than dentin?

A

Yes

More permeable

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4
Q

What percent of cementum is organic, inorganic and water?

A

Inorganic - 65%
Organic - 23%
Water - 12%

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5
Q

What is the structure of hydroxyapatite in cementum?

A

Thin plate like apatite crystals

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6
Q

What are the non-collage ours components of cementum, which are similar to bone?

A

Sialoprotein and osteopntin

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7
Q

What are the 2 types of cementum?

A

Cellular and cellular

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8
Q

What are the 3 types of cementum fibres based of their origin?

A

Extrinsic fibre cementum
Intrinsic fibre cementum
Mixed fibre cementum

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9
Q

What is extrinsic fibre cementum?

A

Only has fibres form outside cementum

Sharpeys fibres from outside the cementum

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10
Q

What is intrinsic cementum?

A

No periodontal ligament fibres inserted into it

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11
Q

What is the common type of cementum fibre?

A

Mixed fibre cementum

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12
Q

What is mixed fibre cementum?

A

Collagen fibres that are deposited by cementoblasts (intrinsic fibres)

Extrinsic fibres form the periodontal ligament

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13
Q

What produces intricacies fibres?

A

Collagen from cementoblasts

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14
Q

How would you classify cementum which has fibres from the periodontal ligament and has no cells present?

A

Acellular extrinsic cementum

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15
Q

How would you classify cementum which has cells present and fibres from the cementoblasts?

A

Cellular intrinsic cementum

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16
Q

What are the 2 categories to classify cementum?

A
  1. Acellular/ cellular
  2. Intrinsic fibres/ extrinsic fibres/ mixed fibres
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17
Q

Can you get afibrillar cementum?

A

Yes

Very rare

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18
Q

Where is cementum mainly located?

A

In the picas area and inter-redicular areas overlying acellular cementum

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19
Q

Where is acellular cementum normallly found?

A

Cervically

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20
Q

What is primary cementum?

A

Acellular

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21
Q

What is secondary cementum?

A

Cellular

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22
Q
A

A = ACELLULAR
B = cellular
C = cementocyte in howships lacunae
D = cementoblasts
E = pre-cementum
F = cementoblasts lining pre-cementum
G = periodontal ligament

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23
Q

What is the dark layer between the cellular and acellular cementum?

A

Afibrillar cementum

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24
Q

What is the hyaline layer

A

hyaline layer of Hopewell-Smith is the most peripheral layer of initially unmineralized dentin that forms immediately subjacent to the cementodentinal junction (CDJ).

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25
Q

What direcention do the canaliculi orientate?

A

Towards periodontal ligament (vascular)

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26
Q

Can the cmentocytes die in the lacunae?

A

Yes, when they get too far from the periodontal ligament and there are empty lacunae left

Hence why farm in the ground section

27
Q

Are cementocytes active or inactive?

A

No

Minute amounts of energy and protein synthesising organelles

28
Q

What are the incremental lines in cementum called?

A

Incremental lines of Salter

29
Q

What do incremental lines of salter represent?

A

Mark differences both in mineralisation and in organic matrix composition

30
Q

Are lines of salter regular?

A

No, especially in cellular cementum

31
Q

What do these lines represent?

A

Incremental Lines of Salter

32
Q

What is the Tomes’ granular layer?

A

Results from the looping and branching of the dentino tubules as a result of the branching of the odontoblastic processes

33
Q

Where does the dark line (afibrillar) locate?

A

Between the hyaline layer and the cementum

34
Q
A

A = dentino-tubules
B = granular layer of tomes’
C = dark line (afibrillar cementum)
D = acellular cementum (closely packed lines of Salter)
E = cellular
F = hyaline layer

35
Q

What are the 2 main sources of the organic matrix?

A

Extrinsic and intrinsic fibres

36
Q

How do the Sharpey’s fibres enter the cementum?

A

Perpendicular or slightly oblique to the root surface

37
Q

How do intarsia fires run in relation to the root surface?

A

Parallel

38
Q

True or Flase, the intrinsic and extrinsic fibres run parallel to one another?

A

False, run at right angles to one another

39
Q
A

Decalcified section: A) Dentine, B) Acellular cementum, C)Periodontal ligament (Principal fibres), D) alveolar bone, E) Ginigival epithelium, White arrows pointing to Sharpey’s fibres in alveolar bone

40
Q

Where is the gingiva and the connective tissue of the gingiva?

A
41
Q

What is this a decalcified section of?

A

Apex of root

42
Q

Where is the cementum, cellular ad mixed fibre cementum?

A

Apex of root, cementum neck to the periodontal ligament

43
Q
A

A) Alveolar bone, B) periodontal ligament, C) Cellular cementum (at the root apex)

44
Q

What is larger, intrinsic or extrinsic fibres?

A

Extrinsic fibres

Sharpey’s fibres

45
Q

Where is the afibrillar cementum found?

A

Thin layer between hyaline layer and acellular cementum

And overlying enamel

46
Q

What type of cementum overlies enamel?

A

Afibrillar cementum

47
Q
A

A = Enamel
B = dentin
C = granular layer of tomes’
D = hyaline layer
E = acellular cementum
F = afibrillar cementum

Ground section

48
Q

What is the origin of the afibrillar cementum?

A

Epithelial cementum

49
Q
A

A = dentin
B = enamel
C = mantle dentin
D = acellular cementum
E = afibrillar cementum
F = hyaline layer

White arrow = granular layer of Tomes

50
Q

How would you describe the interaction of cementum and enamel?

A

Cemento-enamel junction

51
Q

How would you describe the relationship of cementum and dentin?

A

Cemento-dentinal junction

52
Q

What are the three other structures which cementum interacts with?

A

Enable
Dentin
Periodontal ligament

53
Q

What are the 3 possible arrangements of cementum and enamel?

A
  1. Cementum overlaps enamel (60%)
  2. Cementum and enamel meet at butt joint (30%)
  3. Cementum and enamel fail to meet and the dentin between them is exposed (10%)
54
Q

What type of cementum is formed when cementum overlaps enamel?

A

Afibrillar cementum

55
Q

What surface f eagle os more highly mineralised?

A

Aprismatic

No prisms

56
Q
A

A = surface of enamel
B = hunter strager bands
C = enamel stria or stria of fretsius
D = mantle dentin
E = interglobular dentin
F = dentino-tubules

57
Q

What junction is shown here?

A

Cementino-dentinal junction

58
Q
A

A = afibrillar cementum
B = Tomes’
C = Dentino-tubules
D = acellular cementum
E = hyaline / dark line

59
Q

What does the cemento-dentinal junction allow?

A

Anchors periodontal ligament fibre into dentin

60
Q
A

Decalcified section:
A)Dentine
B)Acellular cementum
C)Cellular cementum
D)Reparative cementum at area of resorption
E)Periodontal ligament

61
Q

What can odontocasts resorb?

A

Dentin
Cementum

62
Q

What is a reversal line?

A

The reversal of activity from resorption to deposition (same as bone)

63
Q
A
64
Q

What does repair cementum represent?

A

Cellular cementum

Less mineralised

Smaller crystals