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IOE Dentistry - Dental Anatomy > Cementum > Flashcards

Cementum Flashcards

1
Q

What is cementum?

A

Cementum is the mineralised connective tissue that lines the root of the tooth
It is a highly responsive mineralised tissue, maintaining the integrity of the root and helping to maintain the tooth in its functional position.
Cementum only forms a thin layer on the root

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2
Q

What does the cementum help do?

A

Helps to attach the tooth tot he alveolar bone via the periodontal ligament

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3
Q

Describe the formation of cementum throughout life and what this allows for

A

It is formed slowly but continuously throughout life, and this allows for continual reattachment of the periodontal ligament fibres.

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4
Q

How many tissues make up the periodontium and what are they called?

A

4 tissues make up the periodontal:

  1. Cementum
  2. Alveolar bone
  3. Periodontal ligament
  4. Lamina propria
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5
Q

What components make up cementum?

A 
Cementum contains by wet-weight:
65%
inorganic material 
23% organic material 
12% water
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6
Q

Compare cementum to dentine

A

The tissues in cementum are generally softer and more permeable than dentine but some acellular zones may be more highly calcified than dentine.

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7
Q

What is the principle inorganic component of cementum?

A

The hydroxyapatite crystal

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8
Q

Describe the hydroxyapatite crystals

A

The hydroxyapatite crystals are thin, plate-like and similar to those in bone

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9
Q

Describe the chemical properties of cementum

A

It may be acellular or cellular
It is a vital tissue made up of cementoblasts and cementocytes
Has extrinsic and intrinsic fibres (primarily type I collagen)

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10
Q

State the similarities between cementum and bone

A

They both have a similar chemical composition and similar physicals properties
Both there organic matrix consisting primarily of type I collagen.

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11
Q

State the differences between cementum and bone

A

Cementum is devoid of blood vessels and nerves and is also less readily resorbed, allowing for orthodontic tooth movement.
Cementum does not have a lamellar appearance and has no marrow spaces.

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12
Q

What is the organic matrix of cementum primarily made up of?

A

Collagen

Mostly all is type I but types III, V, VI and XII have been found in small quantities

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13
Q

Describe the non-collagenous elements in cementum

A

They are assumed to be similar those found in bone including sialoprotein, dentine sialoprotein, fibronectin and osteopontin

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14
Q

What are the noncollagenous elements that make up cementum

A

sialoprotein, dentine sialoprotein, fibronectin and osteopontin.

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15
Q

Apart from noncollagenous elements and collagen what else makes up the organic matrix of cementum?

A

Cementum is rich in glycosaminoglycans, predominantly chondroitin sulphate. It also contains proteoglycans and many growth factors.

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16
Q

Where are the collagen fibres in cementum derived from?

A

Cementum derives its collagen fibres from two sources:

  1. From the inserting Sharpey’s fibres of the periodontal ligment
  2. From the cementoblasts
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17
Q

What are collagen fibres from the the sharpey’s fibres of the periodontal ligament called?

A

Referred to as the extrinsic fibres

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18
Q

What are collagen fibres derived from the cementoblasts?

A

Intrinsic fibres

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19
Q

What is mixed fibre cementum?

A

Where both extrinsic and intrinsic fibres are present, the tissue may be termed mixed fibre cementum

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20
Q

What is the precementum?

A

It is a thin layer of uncalcifed matrix on the surface of the cellular variety of cementum

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21
Q

What are the four different ways to classify cementum

A
  1. Cellular and acellular cementum
  2. Primary and secondary cementum
  3. Classifcation based on the presence or absence of cells
  4. Afibrillar cementum
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22
Q

What is the difference between Cellular and acellular cementum?

A

CELLULAR CEMENTUM, contains cells (cementocytes) Cellular cementum forms later, predominantly at and around the root apex and overlying the acellular cement
Cellular cementum is also common in interradicular areas

ACELLULAR CEMENTUM does not contain cells. Acellular cementum is the first formed cementum and forms a relatively thin covering over the whole root

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23
Q

What is the difference between primary and secondary cementum?

A

Acellular cementum is sometimes termed primary cementum

Cellular cementum is sometimes termed secondary cementum.

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24
Q

How can cementum be classified based on the presence or absence of cells

A

Based on the presence or absence of cells and on the nature and origin of the organic matrix:

  1. Acellular extrinsic fibre cementum
  2. Cellular intrinsic fibre cementum
  3. Cellular mixed stratified cementum
  4. Cellular mixed fibre cementum.
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25
Q

What is acellular extrinsic fibre cementum?

A

AEFC is located mainly over the cervical half of the root and constitutes the bulk of cementum in some teeth (E.G. in premolars).
For this type of cementum all the collagen is derived as Sharpey fbres from the periodontal ligament
It corresponds with primary acellular cementum and is formed slowly.

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26
Q

Describe cellular intrinsic fibre cementum

A

CIFC is composed only of intrinsic fibres running parallel to the root surface.
The absence of Sharpey fibres means that intrinsic fibre cementum has no role in tooth attachment.
It may be found in patches in the apical region. It may be a temporary phase, with extrinsic fibres subsequently gaining a reattachment, or may represent a permanent region without attaching fibres.
It corresponds to secondary cellular cementum and is found in the apical third of the root and in the interradicular areas.
CIFC has a layer of cementoid on its outer surface similar to the osteoid seen in bone.

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27
Q

Describe Cellular mixed stratified cementum

A

It is seen most commonly in the apical and the furcation areas of posterior teeth, shows alternation of both the cellular intrinsic fibre cementum and acellular extrinsic fibre cementum.

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28
Q

Describe the Cellular mixed fibre cementum

A

Occasionally normal cellular intrinsic cementum does give attachment to some extrinsic fibres arising from the periodontal ligament.

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29
Q

When and where is afibrillar cementum deposited?

A

May be deposited as a thin layer overlying enamel at the cervical margin of the tooth.

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30
Q

Why might afibrillar cementum form?

A

One explanation for this presumes that the reduced enamel epithelium overlying and protecting this cervical enamel in an unerupted tooth is damaged or lost allowing cells of the dental follicle to come into contact
with the enamel surface where they are induced to form cementoblasts.

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31
Q

Describe acellular cementum

A

Has no cells
Border with dentine not clearly demarcated
Rate of development relatively slow
Incremental lines relatively close together
Precementum layer virtually absent

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32
Q

Describe cellular cementum

A

Lacunae and canailculi containing cementocytes and their processes
Border with dentine with dentine clearly demarcated
Rate of development relatively fast
Incremental lines relatively wide apart
Precementum layer present

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33
Q

Which type of cementum, acellular or cellular have a faster rate of development?

A

Cellular cementum

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34
Q

How does the periodontal ligament fibres attach to the cementum?

A
  1. The unmineralised fibres of the periodontal ligament run into the organic matrix of precementum that is secreted by cementoblasts.
  2. Subsequent mineralisation of precementum will incorporate the extrinsic fibres as Sharpey fibres.
  3. These fibres are mineralised within the cementum but unmineralised in the ligament. They are formed by periodontal fibroblasts and their orientation differs from those fibres produced by cementoblasts.
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35
Q

Where are Sharpey’s fibres abundant?

A

Sharpey’s fibres are abundant in acellular cementum.

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36
Q

What is the role of cellular cementum?

A

Cellular cementum is usually present as intrinsic fibre type and does not act in a supportive role as no Sharpey’s fibres from the periodontal ligament are inserted into it.

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37
Q

What are Sharpey’s fibres?

A

The ends of the periodontal ligament fibres inserted into root cementum and alveolar bone of the tooth socket are known as Sharpey’s fibres.

38
Q

In what rhythm is cementum deposited in and what does this cause?

A

Cementum is deposited in an irregular rhythm, resulting in unevenly spaced incremental lines of Salter

39
Q

What is the periodicity between the incremental lines?

A

Unknown

40
Q

Describe the incremental lines found in acellular cementum?

A

In acellular cementum, incremental lines tend to be close together, thin and even

41
Q

Describe the incremental lines found in cellular cementum?

A

The lines are further apart, thicker and more irregular

42
Q

When does formation of the cementum begin?

A

When the crown has fully formed

43
Q

Describe the steps involved in the formation of cementum

A
  1. The internal and external enamel epithelia proliferate downwards as a double-layered sheet of somewhat flattened epithelial cells, the epithelial root sheath (of Hertwig) that outlines the shape of the root.
  2. The epithelial root sheath induces the peripheral cells of the dental papilla to differentiate into odontoblasts and begin producing predentine.
  3. The epithelial root sheath is in contact with the initial predentine layer for only a short time before the continuity of its cells is lost.
44
Q

What does the epithelial root sheath of Hertwig induce?

A

The epithelial root sheath induces the peripheral cells of the dental papilla to differentiate into odontoblasts and begin producing predentine. The epithelial root sheath is in contact with the initial predentine layer for only a short time before the continuity of its cells is lost.

45
Q

What starts the formation of cementum?

A

Once the crown has fully formed, the internal and external enamel epithelia proliferate downwards as a double-layered sheet of somewhat flattened epithelial cells, the epithelial root sheath (of Hertwig) that outlines the shape of the root.

46
Q

Describe how acellular cementum is formed

A
  1. Mesenchymal cells of the inner layer of the dental follicle, come to lie close to the surface of the newly formed un-mineralised dentine
  2. These differentiate into cementoblast-like cells, secrete collagen fibrils and begin forming acellular cementum.
  3. At their deep surface, collagen fibrils intermingle with those of the hyaline layer, while at their superficial end these fibrils extend perpendicularly into the periodontal space and provide attachment for fibres of the
    PDL.
47
Q

What do collagen fibres do at their deep surface during acellular cementum formation?

A

At their deep surface, these fibrils intermingle with those of the hyaline layer,

48
Q

What do collagen fibres do at their superficial surface during acellular cementum formation?

A

Collagen fibrils extend perpendicularly into the periodontal space and provide attachment for fibres of the
PDL.

49
Q

What happens following acellular cementum finishes forming?

A

Following the formation of acellular cementum in the cervical portion of the root, cellular cementum appears in the apical region of the root at about the time the tooth erupts.

50
Q

When does cellular cementum formation begin?

A

Following the formation of acellular cementum

In the apical region of the root at about the time the tooth erupts.

51
Q

Describe the formation of cellular cementum

A
  1. Following the loss of continuity of the epithelial root sheath, large basophilic cells are seen
    to differentiate from the adjacent cells of the dental follicle against the surface of the root dentine (or acellular cementum).
  2. These cells form a more distinct cuboidal layer of cementoblasts adjacent to the root surface and secrete the collagen that forms the intrinsic fibres of the cellular cementum.
  3. These fibres are oriented parallel to the root surface and do not extend into the periodontal ligament.
52
Q

Does resorption occur in the cementum?

A

Cementum is not normally subject to resorption
But localised, small areas of resorption (may be associated with microtrauma) can sometimes be seen on the roots of permanent teeth.

53
Q

What is the resorption carried out by in cementum?

A

Carried out by multinucleated odontoclasts and may continue into the root dentine.

54
Q

How is the problem of resorption deficiencies tackled in cementum?

A

Resorption deficiencies may be filled by deposition of mineralised tissue.

55
Q

What can be seen separating the repair tissue from the normal underlying dental tissues?

A

A reversal line

56
Q

Describe the appearance of reversal lines

A

Irregular
Dark
Staining lines

57
Q

How does repair happen in the cementoblast?

A

Repair occurs as a layer of cementoblasts deposit a thin layer of matrix (precementum) in the deficiency.

58
Q

Which cells carry out repair in the cementum?

A

Cementoblasts

59
Q

Describe the repair tissue in cementum formed after the repair of the cememtum

A

The repair tissue can resemble cellular cementum with evidence of appositional growth.

60
Q

Where is cementum found?

A

It covers the root of the tooth

It begins at the cervical portion at he the cej and it continues to the apex

61
Q

Where is cementum thickest?

A

Thickest at the apex

150-200 micrometres

62
Q

Where is cementum thinnest?

A

Cervical

20-50 micrometres

63
Q

What is the colour of the cementum?

A

Pale yellow

64
Q

What makes up the inorganic component of cementum?

A

Ca and Ph which makes up the hydroxyapatite crystals

65
Q

Which non-collagenous organic component is unique only to cementum?

A

Cementum derived adjustment protein

66
Q

What is the function of the non collagenous components that make up dentine?

A

They mainly help in matrix deposition
further matrix remodelling
Remineralisation

67
Q

Which proteoglycans are present in the cementum?

A

Chondroitin sulfate

Heparam sulfate

68
Q

Which growth factors are present in the cementum?

A

TGF
FGF
IGF

69
Q

What are the cells that form cementum called?

A

Cementocyte

70
Q

Describe the extrinsic collagen fibres in cementum

A

When derived from the periodontal ligament, the fibres are referred to as the extrinsic fibres. These Sharpey’s fibres continue into the cementum in the same direction as the principal fibres of the ligament

71
Q

Describe the intrinsic collagen fibres in cementum

A

When derived from the cementoblasts, the fibres are referred to as intrinsic fibres. These run parallel to the root surface and approximately at right angles to the extrinsic fibres.

72
Q

What is it called both extrinsic and intrinsic fibres are present?

A

Mixed fibre cementum

73
Q

What is the thin layer of uncalcifed matrix on the surface of the cellular variety of cementum called?

A

Precementum

74
Q

What is the fibre inserted into theroot cementum and alveolar bone of the tooth socket called?

A

Sharpey’s fibres

75
Q

What forms the attachment for fibres of the PDL in the cementum?

A

collagen fibres do at their superficial surface during acellular cementum formation extend perpendicularly into the periodontal space and provide attachment for fibres of the
PDL.

76
Q

What can cause reposition to occur and where does it usually occur in cementum?

A

May be due to microtrauma leading to small localised areas of resportio being seen on the roots of the permanent teeth

77
Q

When is a reversal line visible in cementum?

A

can be seen separating the repair tissue from the normal underlying dental tissues

78
Q

What are the 3 main types of cementum?

A
  1. Acellular extrinsic fibre cementum
  2. Cellular intrinsic fibres cementum
  3. Acellular afibrillar cementum
79
Q

Describe the incremental in acellular extrinsic fibre cementum

A

Run parallel to the surface and are very close to each other due to the slow formation of AEFC

80
Q

Where are cellular intrinsic fibres cementum

A

Apical 1/3 area of the root

81
Q

Which cementum fibre is termed the primary cementum?

A

Acellular extrinsic fibre cementum

82
Q

Describe the incremental in Cellular intrinsic fibres cementum?

A

Far apart from each

83
Q

What is the function of Cellular intrinsic fibres cementum?

A

Adaptation and repair

84
Q

Which cementum fibre is termed the secondary cementum?

A

Cellular intrinsic fibres cementum

85
Q

Where are Acellular extrinsic fibre cementum

A

CEJ to the apical 1/3 region of the tooth

86
Q

What is the function of Acellular extrinsic fibre cementum?

A

Anchorage

87
Q

Which trace element is highest in the cementum than any other calcified tissue?

A

Fluoride

88
Q

What are the functions of cementum?

A
  1. Providing an attachment site for the periodontal ligament
  2. Protecting the underlying tissues
  3. Maintains the length of the periodontal space
  4. Repair minor fractures in the root
89
Q

Which 3 cells make up cementum?

A

Cementoblasts
Cementocytes
Odontoblasts

90
Q

When can sensitivity arise?

A

When there is a gap between the cementum and the enamel leaving some of the underlying dentine exposed

IOE Dentistry - Dental Anatomy (6 decks)

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