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Oral Biology > Components of the Teeth - Cementum > Flashcards

Components of the Teeth - Cementum Flashcards

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1
Q

what are the features of cementum

A
  • cementum covers the root dentine
  • it has a very similar structure to bone
  • provides attachment for some periodontal fibres
  • laid down by cementocytes
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2
Q

in what way is the structure of cementum similar to bone

A

both have a collagen matrix as well as a lamellar arrangement, which means they go around in circles

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3
Q

what are the two different types of cementum

A

cellular and acellular

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4
Q

give a brief description of cellular cementum

A

this form of cementum contains cementocytes, is present in the apical part of the root and is later formed (known as secondary cementum)

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5
Q

give a brief description of acellular cementum

A

there are no cells, it lies adjacent to dentine and is the primary cementum, ie the first formed cementum

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6
Q

what is furcation

A

this is where the roots of molars will fork

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7
Q

give a brief description of the acellular extrinsic fibre cementum

A

this means that the fibres are coming from outside into the cementum, anchoring onto it.
these fibres are collagen fibres known as Sharpey’s fibres, and are equivalent to primary acellular cementum
they are present on cervical roots.

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8
Q

what is the key difference between acellular and cellular cementum

A

acellular does not have cells within, but it does have Sharpey’s fibres. cellular does have cells but it does not have Sharpey’s fibres

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9
Q

give a brief description on cellular, intrinsic fibre cementum

A

there are no collagen fibres, but there are intrinsic collagen fibres that run parallel to the surface. this is equivalent to the secondary cellular momentum.
this has no role in tooth attachment, as the fibres can not get out of the cementum, therefore meaning the collagen fibres are not able to attach to the bone on the other side

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10
Q

what are cementocytes

A

these are the cells that form cementum, and can also be called cementoblasts, although this is not recommended.

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11
Q

in what form of cementum are the cementocytes actively building up cementum

A

the cellular cementum

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12
Q

how can the production of cementum be described

A

in waves, which leads to the mixture of cellular and acellular

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13
Q

how can cementum, enamel and dentine be linked

A
  • cementum can be covering the enamel at the cervix of the tooth
  • cementum can be just meeting enamel
  • there can be a space between the cementum and the enamel which leads to exposed dentine
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14
Q

how is the tooth attached to the bone

A

via periodontal fibres known as sharpey fibres which attach to the alveolar bone

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15
Q

does the formation of cementum stop once the tooth has erupted

A

no, it is slowly formed throughout life which allows for the reattachment of periodontal ligament

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16
Q

what is one of the features of cemental growth that allows for the reattachment of periodontal ligament

A

it is slowly formed throughout life

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17
Q

what can occur to cementum if exposed to the oral environment

A

due to the relative softness of cementum, combined with its thinness cervically, it can be readily removed by abrasion when gingival recession exposes the root surface to the cellular cementum

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18
Q

what are the lacunae in the cementum

A

these are the spaces that cementocytes occupy in the cellular cementum

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19
Q

how does cementum compare with the other dental tissues

A

its crystallinity of apatite is lower, and it can be demineralised more easily

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20
Q

what are the four tissues responsible for supporting the tooth in the jaw

A
  • cementum
  • alveolar bone
  • periodontal ligament
  • gingivae
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21
Q

describe the regional thicknesses of cementum

A

it is thickest at the root apex and thinnest cervically

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22
Q

is cementum permeable

A

yes, more so than dentine is, however this permeability declines with age

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23
Q

what is the prime function of cementum

A

give attachment to the collagen fibres of the periodontal ligament

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24
Q

what is cementoid

A

the layer of unmineralised matrix

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25
Q

which area of the root is cellular cementum found

A

in the apical area of the root

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26
Q

where is acellular cementum found

A

covering the toot adjacent to dentine

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27
Q

what are the structural differences between cellular and acellular cementum though to be related to

A

the faster rate of matrix formation

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28
Q

where are extrinsic fibres derivded from

A

the periodontal ligament

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29
Q

where are intrinsic fibres derived from

A

cementoblasts

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30
Q

what feature of cementum allows the reattachment of the periodontal ligament throughout life

A

it is slowly formed throughout life

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31
Q

what features of cementum mean it is readily removed by abrasion when the gingival recession exposes the root surface to the oral environment

A

it is relatively soft and thin cervically

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32
Q

what are lacunae

A

the spaces that cementocytes occupy in the cellular cementum

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33
Q

how does the crystallinity of the hydroxyapatite in cementum compare to the other dental tissues

A

it is lower

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34
Q

where is the thickest region of cementum located

A

root apex

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35
Q

where is the thinnest region of cementum located

A

cervical region

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36
Q

is cementum more or less permeable than dentine

A

more

37
Q

what is the prime function of cementum

A

to give attachement to collagen fibres of the periodontal ligament

38
Q

what is the cementoid

A

the layer of unmineralised matrix in the cementum

39
Q

where are extrinsic fibres derived from

A

periodontal ligament

40
Q

where are intrinsic fibres thought to be derived from

A

cementoblasts

41
Q

where is cementum located and what is its function

A

it is found lining the root of the tooth to help the attach the tooth to the alveolar bone via the periodontal ligament

42
Q

what does the organic matrix of cementum consist primarily of

A

type one collagen

43
Q

what kind of tissue can cementum be described as

A

calcified

44
Q

what is cementum derived from

A

the investing layer of the dental follicle

45
Q

describe the appearance of cementum

A

pale yellow, dull surface

46
Q

is cellular less permeable than acellular cementum

A

no

47
Q

how much of the weight of cementum is inorganic material

A

65%

48
Q

how much of the weight of cementum is organic material

A

23%

49
Q

how much of the weight of cementum is water

A

12%

50
Q

what is the principle inorganic component of cementum

A

hydroxyapatite

51
Q

does cementum demineralise easier than the other dental tissues

A

yes

52
Q

describe the fluoride levels of cementum

A

high

53
Q

what is cementum derived attachment protein

A

a collagenous protein that promotes the attachment of mesenchymal cells to the extracellular matric.

54
Q

where is the cementum derived attachment protein found

A

in the matrix of mature cementum and in cementoblasts

55
Q

describe the presence of growth factors in cementum

A

there are many, and they are normally locked up and remain inactive due to low turnover rate

56
Q

how is cementum deposited

A

in an irregular rhythm

57
Q

what are there unevenly spaced incremental lines on cementum

A

because it is deposited in an irregular rhythm.

58
Q

what is the appearance of incremental lines mainly due to

A

the differences in the degree of mineralisation, which must also reflect the differences in composition of the underlying matrix, since the lines are readily visible in decalcified sections

59
Q

give a summary on cellular cementum

A
  • contains cementocytes
  • covers the apical area of the root, overlying the acellular cementum
  • also called secondary cementum
  • in rapidly formed cellular cementum, the incremental lines tend to be closer together, thin and even
60
Q

give a summary on acellular cementum

A
  • does not contain cementocytes
  • covers the root adjacent to the dentine
  • also called primary dentine
  • structureless
  • dark line may be discerned between the hyaline dentine and the acellular cementum
61
Q

which cementum is formed first

A

acellula

62
Q

what is the function of canaculi

A

connecting the lacunae together

63
Q

how are the canaculi of the acellular cementum orientated

A

preferentially toward the periodontal ligament

64
Q

what is the chief source of nutrients for the canaculi of the acellular cementum

A

the periodontal ligament

65
Q

what is the organic matrix derived from

A

two different sources
- sharpey fibres of the periodontal ligament
- cementoblasts

66
Q

what are extrinsic fibres

A

fibres derived from the periodontal ligament that continue into the cementum in the same direction as the principle fibres of the ligament

67
Q

what are intrinsic fibres

A

fibres derived from cementoblasts that run parallel to the root at right angles to the extrinsic fibres

68
Q

what is the name of the cementum where both extrinsic and intrinsic fibres are located

A

mixed fibre cementum

69
Q

what are the differences between acellular and cellular cementum

A

acellular:
- no cells
- no clear border with dentine
- slow development
- close incremental lines
- almost absent precementum

cellular:
- cementocytes and processes found in lacunae and canaculi
- border with dentine is clear
- fast rate of development
- wide incremental lines
- precementum layer is present

70
Q

describe the acellular extrinsic fibre cementum

A

all collagen derived from sharpey fibres from the periodontal ligament
corresponds with acellular cementum
covers the cervical two thirds of the root
formed slowly

71
Q

describe the cellular intrinsic fibre cementum

A

composed only of intrinsic fibres running parallel to the root surface
absence of sharpey fibres means the intrinsic fibre cementum has no role in tooth attachment
found in patches in the apical region
generally corresponds to the secondary cellular cementum

72
Q

describe mixed fibre cementum

A

collagen fibres of the organic matrix are derived from both extrinsic and intrinsic fibres
acellular mixed fibre cementum is the name if the formation is slow

73
Q

describe afibrillar cementum

A

no collagen fibres, instead consists of a well minerailsed ground substance that may be of epithelial origin
thought to be formed at this site following the loss of reduced enamel epithelium

74
Q

how do the periodontal ligament fibres attach to the cementum

A

the fibres of the periodontal ligament run into the organic matric of the precementum is secreted by cementoblasts, and the subsequent mineralisation of the precementum will incorporate the extrinsic fibres as sharpey fibres

75
Q

why is the cementum dentine junction of clinical importance

A

because of the processes involved in maintaining tooth function while repairing a diseased root surface

76
Q

describe the mineral content of the cementum dentine junction

A

low

77
Q

describe the resorption of cementum

A
  • less susceptible to resorption than bone under the same pressures
  • carried out by multinucleated odontoclasts
  • may continue into the root dentine
  • different levels of fluoride in cementum and bone may explain why cementum is less susceptible to resorption
78
Q

why is the surface of cementum relatively inaccessible

A

the surface of cementum is covered by a layer of tightly packed collagen

79
Q

what does cementum repair tissue resemble

A

cellular cementum

80
Q

describe exposed root dentine

A

the cementum may not completely cover the dentine around the entire circumference of the cervical margin, and can be easily abraded away. these conditions lead to the exposure of the dentine tubules to the oral environment. if the tubules are patent, this may give rise to the painful symptoms of hypersensitivity

81
Q

describe root fractures

A

the most common cause of root fractures is physical trauma from sports, falls or fights. most often it involves anterior teeth. the plane of fracture may be horizontal or vertical and may lead to mobility in the fractured part of the tooth. dental pulp often retains its vitality

82
Q

what are cementicles

A

small, globular masses of cementum found in approximately 35% of human roots. it may be located on the cementum surface or be free within the periodontal ligament. they can occur from microtrauma when extra stress on the sharpey fibres cause a tear in the cementum.
they are more common in the apical and root furcation areas

83
Q

describe how cementum is involved in regeneration of the periodontal ligament

A

in the removal of subgingival calculus, care must be taken to limit the removal of cementum.
stem cells associated with the formatio of cementum resides in the periodontal ligament

84
Q
A
85
Q

is cementum harder than dentine

A

no it is softer

86
Q

is cementum vascualar

A

no

87
Q

what is precementum

A

a thin layer of uncalcified matrix on the surface of the cellular cementum

88
Q

is cementum innervated

A

no

Oral Biology (27 decks)

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