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Dental Histology > Lecture 5 & 6 > Flashcards

Lecture 5 & 6 Flashcards

1
Q

Thickness of cementum?

A

20um at CEJ, 200um at apex

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2
Q

T/F - Dentine is covered by cementum in cervical region of tooth

A

False - it covers dentine in roots of teeth

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3
Q

Cementum is vascular like bone

A

False - it is avascular

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4
Q

Cementum has a nerve supply

A

False - does not have nerves

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5
Q

T/F - Cementum has similar consistency and hardness to bone

A

True

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6
Q

Is cementum sporadically cellular

A

True

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7
Q

T/F - Cementum readily remodels

A

False, it does not readily remodel. But it can remodel on a very small scale (applied in orthodontic treatments) to accommodate reattachment of periodontal collagen (Sharpey’s fibres)

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8
Q

Sharpey’s fibres are periodontal collagen

A

True

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9
Q

Cementum is formed quickly throughout life T/F

A

False

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10
Q

Cementum life formation can result in a gradual thickening that is approximately two-fold

A

False, it results in thickening of approximately three-fold.

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11
Q

What are the features of cementum?

A

Matrix and cells

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12
Q

What does matrix consist of?

A

Ground substance and collagen

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13
Q

T/F - some collagen is intrinsic in fully-formed cementum, some is extrinsic

A

True

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14
Q

Extrinsic cementum are ends of collagen fibres which do not extend into PDL

A

True

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15
Q

Ground substance is dissimilar to bone

A

False

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16
Q

Cementoblasts are located within cementum, which produces cementum

A

False, they are located on surface of cementum

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17
Q

Cementocytes are located on surface, and breakdown cementum

A

False, they are located within cementum, and produce cementum

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18
Q

Cementoclasts/odontoclasts are located on surface of cementum and produce cementum

A

False, they are located on surface of cementum but they breakdown cementum

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19
Q

Cementoblasts produce matrix T/F

A

True

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20
Q

Matrix consists of inorganic ground substance and intrinsic collagen

A

False - it’s organic ground substance!

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21
Q

T/F - Some collagen in cementum is derived from periodontal ligament fibroblasts which are intrinsic fibres

A

True in first half, false for fibroblasts - they are extrinsic fibres.

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22
Q

T/F - Cementoblasts produce matrix vesicles which are not involved in mineralization.

A

False, they do play in mineralization.

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23
Q

Cavities in cementum are called ?

A

Lacunae

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24
Q

Long processes in cementum are called?

A

Canaliculi

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25
Q

Lacunae and canaliculi are directed towards source of nutrition - T/F

A

True, the blood vessels in the periodontal ligament

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26
Q

Adjacent canaliculi are often connected - T/F

A

True

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27
Q

Gap junctions exist between processes of adjacent cells

A

True

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28
Q

Cementocytes in deeper parts of cementum do not degenerate normally and die

A

False

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29
Q

Osteocytes in deeper parts of bone remain viable

A

True

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30
Q

Lacunae are variable in size and shape but usually 10-30um

A

False, they are usually 7-20um.

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31
Q

Cementoclasts are single nucleate cells derived from blood monocytes as are other phagocytic cells

A

False - Cementoclasts are multinucleate

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32
Q

T/F - Cementoclasts/odontoclasts exist on cementum surface, and are comparatively common since cementum readily undergoes remodelling.

A

False - cementoclasts are uncommon, since cementum does not readily undergo remodelling

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33
Q

Most roots of permanent teeth show small areas of ________ which may extend into dentine. Cause unknown but may be result of _______

A

FOCAL CEMENTUM RESORPTION. local microtrauma

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34
Q

Regions of focal resorption may be subsequently be repaired by _________

A

cementoblasts

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35
Q

___________ extends from periodontal ligament into cementum.

A

Extrinsic collagen

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36
Q

Extrinsic collagen is formed by ____________

A

periodontal fibroblasts, collagen forms first, cementoid/cementum is laid down around it

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37
Q

Coarse fibres of extrinsic collagen are ________ (diameter)

A

5-7um diameter

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38
Q

__________ is a general term for collagen which is partly embedded in mineralised tissue and partly in general connective tissue

A

Sharpey’s fibres

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39
Q

___________ is totally within cementum. It is formed by cementoblasts/cytes. It’s ____ fibres are _____ (diameter)

A

Intrinsic collagen. Fine, 1-2 um diameter

40
Q

Cementum is classified on the basis of three factors:

1) whether it incorporates cells (cementocytes)
2) whether it contains collagen fibres
3) whether collagen within cementum consists of large or smaller fibres

A

1) acellular/cellular
2) fibrillar/afibrillar
3) extrinsic fibres/intrinsic fibres

41
Q

What are the two common types of cementum in humans?

A

acellular extrinsic fibre cementum + cellular intrinsic fibre cementum

42
Q

Summarise acellular extrinsic fibre cementum (AEFC)

A

No cells,
sharpeys fibres only (can be seen in LM),
cervical 2/3 of root

43
Q

Summarise cellular intrinsic fibre cementum

A

contains cementocytes,
intrinsic fibres only (not visible in LM without special staining,
in apical part of root

44
Q

When does cellular intrinsic fibre cementum form?

A

During latter part of root development.

45
Q

When does acellular extrinsic fibre cementum form?

A

Forms during earlier part of root development, usually found in apical part of root

46
Q

AEFC forms comparatively _____ and consists of closely packed ____________ Sharpey’s fibres embedded in _______

A

slowly, fully calcified, cementum matrix

47
Q

CIFC forms during the _____ part of root development and is usually found in ______ part of root and is often interspersed with ________________

A

latter, apical, cellular mixed fibre cementum

48
Q

Cellular mixed fibre cementum consists of _________ containing ___________ oriented mostly parallel to the surface, plus _______ containing cementocytes. Their __________ processes are contained within ________ which are mostly oriented towards the ________ ligament. Cellular _______ may not be present in ______ rooted teeth.

A

cementum matrix, fine intrinsic collagen, lacunae, long cytoplasmic, canaliculi, periodontal, cementum, single

49
Q

Summarise CELLULAR MIXED FIBRE CEMENTUM

A

Contains:

1) cells
2) both extrinsic and intrinsic fibres
3) identify in LM by presence of both cells and extrinsic fibres
4) apex and bifurcation of root

50
Q

CMFC usually forms later at the _____ & ______ of the root & is often interpersed with other types of cementum. Consists of cementum matrix containing a mix of ___________ oriented obliquely or at right angles to the surface plus _________ plus ________ and their canaliculi and lacunae.

A

Apex, bifurcation, large extrinsic fibres, small intrinsic fibres, cementocytes

51
Q

Summarise ACELLULAR AFIBRILLAR

A
  • no cells
  • probably no collagen
  • very restricted in location - cemento-enamel junction
52
Q

Acellular fibrillar cementum can only be recognised with certainty in EM, but is generally described as being mostly restricted to the _________. This type of cementum is reported as lacking __________

A

Cementoenamel junction (CEJ), collagen fibres

53
Q

Alternative terminology for cementum. _______ is restricted to first formed cementum, and others to describe cementum formed prior to formation of some or all of the root.

A

primary and secondary cementum

54
Q

T/F - Cementum is laid down slowly throughout life but does readily remodel.

A

False - it does not readily remodel

55
Q

Cementodentinal junction can be recognized by adjacent __________________ in _______. There is also a very thin structureless, highly layer of mineralized tissue between cementum and dentine - ______________.

A

granular layer of Tomes, root dentine, hyaline layer of Hopewell-Smith

56
Q

Hyaline layer of hopewell-smith is _____ thick. It is the product of ___________ not cementoblasts. It is an organic matrix more like ______ than dentine (amelogenins). It is more mineralized than _____ and mineralizes later than the adjacent _______. Its function is adhesion of _______ and ______. It can sometimes be recognized on demineralized sections as ______ or poorly stained line between ______ &_____.

A

10-20 um, epithelial root sheath cells, enamel, dentine, mantle dentine, cementum, dentine, thin unstained, root dentine, cementum

57
Q

___________ can form in cementum but do not have the regular pattern or specific names of ______ in other parts of tooth.

A

Incremental lines

58
Q

About 35% of human roots incorporate small globular masses of cementum called _________, either in the ______ ligament or attached to or wholly within cementum.

A

cementicles, periodontal

59
Q

In some instances, cementum may thicken excessively forming ________ on surface of normal cementum which may complicate _______

A

hypercementosis, extractions

60
Q

Hypercementosis thickenings are usually ______, but in some abnormal conditions, e.g. _______ may be quite extensive

A

local, Paget’s disease

61
Q

Orthodontic movements & Mesial drift:
bone is resorbed on the side of pressure, either due to an orthodontic device or to _____ forces, which cause teeth to drift ______ with time

A

occlusal, mesially (move inwards)

62
Q

What are the features of periodontal ligament?

A

Connective tissue attachment between tooth and aveolar bone,
consists of general connective tissue
provides mechanical protection against excessive occlusal load,
has proprioreceptors which play a role in regulating jaw reflexes

63
Q

Fibroblasts are involved in _________ - laying down, maintenance, breakdown.

A

Collagen remodelling - allows for tooth movements and eruption

64
Q

Fibroblasts have ________ nuclei which are mostly aligned with direction of __________ which are best seen in the light microscope, however there are an extensive ______________ as well.

A

elongated, collagen fibres, branches cytoplasm

65
Q

Undifferentiated cells can differentiate into ______, ______ or _______

A

fibroblasts, osteoblasts, cementoblasts

66
Q

_____________ are groups of epithelial cells in the periodontal ligament, which are remnants of Hertwigs Epithelial Root Sheath (this is part of _______ which is involved in root formation. Hertwig’s epithelial root sheath mostly breaks down after root formation, but some remnants are normal.

A

Rests of Malassez, enamel organ

67
Q

Rests of Malassez are recognized as tightly packed groups of _____________. If viewed three dimensionally, often forms a network of ______ with a dense nucleus, joined by _______ & _________.

A

deeply staining nuclei, small dark cells, desmosomes, gap junctions,

68
Q

Rests of Malassez are surrounded by a ___________ - not visible in light microscope without special staining

A

basal lamina

69
Q

T/F - Rests of Malassez have a close relationship with nerve endings and small blood vessels

A

True

70
Q

T/F - there is evidence that rests of Malassez are involved in BOTH periodontal pathologies and in normal maintenance of periodontium.

A

True

71
Q

T/F - Periodontal ligament fibres are comprised of collagen and mature and functional elastin called ________

A

False, its immature, and its called oxytalin fibres

72
Q

T/F - Collagen of periodontal ligament is not highly oriented

A

False

73
Q

Periodontal ligament: gaps between collagen bundles are _________

A

Interstitial tissue (sometimes interstitial spaces, but they are areas of loose CT

74
Q

T/F - Collagen fibres insert into bone at one end and cementum at the other. Inserted fibres are called sharpey’s fibres!

A

True

75
Q

T/F - Sharpey’s fibres in cementum are not finer than bone

A

False

76
Q

T/F - Collagen has a slow turnover, fine collagen fibrils intertwined like the fibres which form the subunits of a rope.

A

False, they have a rapid turnover

77
Q

What is the average width of collagen bundles/fibres?

A

About 5um, but can be very variable between teeth, within a tooth and with age

78
Q

What is oxytalin?

A

Immature elastin

79
Q

What is oxytalin produced by?

A

Fibroblasts

80
Q

How is oxytalin oriented?

A

It is mostly oriented longitudinal in the periodontal ligament.

81
Q

Can oxytalin attach to bone?

A

Rarely, and it may attach to cementum

82
Q

T/F - Oxytalin is closely associated with periodontal blood vessels, and may play a role in regulating blood flow.

A

True

83
Q

T/F - Fibre groups of periodontal ligament function to retain tooth in socket and resist lateral, vertical and shearing forces

A

True

84
Q

T/F - Alveolar crest group exists between cementum to bone in a coronal direction, and are the most numerous

A

False, they exist between cementum and rim of alveolus, just below CEJ. Alveolar crest group resists horizontal movement.

85
Q

T/F - Horizontal group exists between cementum to bone just below alveolar crest

A

True, resists horizontal movement.

86
Q

T/F - Oblique group exists between apex of root to bone of socket.

A

False, it exists between cementum to bone in a coronal direction and is the most numerous.

87
Q

T/F - Oblique group of periodontal ligament fibres resists horizontal pressure/movement

A

False, they resist vertical pressure which could drive root into socket.

88
Q

T/F - Interradicular group is located at the bifurcation of root to interradicular septum.

A

True

89
Q

T/F - Apical and interradicular group of fibres both help to stabilise tooth in socket.

A

True.

90
Q

T/F - Venous and lymph drainage is into the bone of the alveolus

A

True

91
Q

T/F - Minor arteries supply the maxillary and mandibular teeth

A

False, superior and inferior alveolar arteries supply the teeth.

92
Q

T/F - Branches of superior and inferior alveolar arteries pass within the alveolar bone and through foramina vertically into the periodontal ligament, but they do not form a capillary plexus.

A

False, they pass horizontally into the ligament and they do form a capillary plexus.

93
Q

T/F - Both blood and lymph vessels have an endothelial lining and lumen

A

True

94
Q

T/F - periodontal ligament have mechanoreceptors, both free-endings (schwann cells without fibrous capsule) and encapsulated endings

A

True

95
Q

____________ generally have a collagen capsule - the axon within branches to form fine _________ with interspersed collagen. _________ displaces the collagen and the axon terminals respond.

A

encapsulated endings, intertwined endings, mechanical stress

96
Q

T/F - periodontal ligament nerves are sympathetic (vasomotor) and parasympathetic

A

True

97
Q

T/F - Periodontal ligament does not narrow with age

A

False, it does narrow.

Dental Histology (7 decks)

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