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SKA > Week 11 > Flashcards

Week 11 Flashcards

1
Q

What does the periodontium consist of?

A

Hard tissue:
-cementum
-alveolar bone
Soft tissue:
- Periodontal ligament
-gingiva

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2
Q

Function of the cementum?
Is it calcified?
Is it vascular?

A

attaches the teeth to the alveolar process by anchoring the PDL
It is calcified and avascular mesenchymal tisssue that forms the outer covering of the root
Provide a protective cover over the open dentinal tubules within the root dentin if exposure occurs.

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3
Q

Physical properties of cementum?
Where is it thickest?
Where is it the thinnest?
Due to it’s mineral levels, cementum appears ….
Permeability?

A

Cementum is a hard tissue
it’s thickest at the root apex and in the inter radicular areas of multirooted teeth (50 to 200 micrometres)
it’s thickest at the cementoenamel junction

(radiolucent) and therefore a darker colour than enamel and dentin

✓Permeable from dentin and PDL sides
✓Cellular cementum is more permeable than acellular cementum

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4
Q

Chemical composition of the cementum?

A

45-50% inorganic material
50% organic material

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5
Q

Chemical composition of cementum( in depth)

A

This crystalline formation of mature cementum consists mostly of
calcium hydroxyapatite with the chemical formula of Ca10(PO4)6(OH)2
* The organic components include collagen, glycoproteins, and
proteoglycans, mostly Type I collagen
* Cementum contains the greatest amount of fluoride in all mineralized
tissues

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6
Q

What are the three functions of cementum?

A
  • Anchorage— In both types, Sharpey fibers
    allow anchorage of the tooth within the
    osseous socket
  • Adaptation— mainly achieved by cellular
    cementum. By continuous deposition,
    especially in apical and furcation areas,
    cellular cementum compensates for
    tooth wear that causes tooth eruption to
    facilitate contact with the opposing tooth
    at the existing occlusal plane
  • Repair— mainly achieved by cellular
    cementum
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7
Q

Cementogenesis

A

Production of predentine by odontoblasts in developing root leads to the breakdown of HERS (Hertwig epithelial root sheath)
* Then, mesenchymal cells of the dental follicle differentiate into cementoblasts which deposit collagen fibrils – leading to
– pre cementum formation
* As one layer of pre cementum is formed, the old one calcifiesto become cementum
* Growth of the cementum is incremental

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8
Q

Acellular cementum
Is it the first cementum formed?
How much of the tooth surface does it cover?
What does it consist of?
What is it’s thickness ?
What makes up most of the structure? and what is it’s role?

A

It is the first cementum formed
* It covers approximately the cervical third or
half of the root and does not contain cells
* It consists of the first layers of cementum
deposited at the Dentino-Cemental Junction
and thus is also referred to as primary
cementum.
* Its thickness ranges from 20- 50µ
* Sharpey’s fibers make up most of the
structure of acellular cementum, and their
role is to support the tooth

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9
Q

Cellular cementum
what is it also referred to as?
What does it consist of?
how much of the tooth surface does it cover?
What is the thickness?
is it more or less permeable than acellular cementum
Is it formed at a faster or slower rate that acellular?

A
  • It is referred to as Secondary Cementum
  • It consists of the last layers of cementum
    deposited over the acellular cementum
  • Covers the apical one-third of each root
  • Thickness 150-200µ
  • More permeable than acellular
    cementum
  • It is formed at a faster rate than acellular
    type
    Cellular cementum consists of
    Cementocytes
  • Cementocytes are enclosed
    within lacunae with processes
    in canaliculi directed toward
    the tooth surface
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10
Q

Acellular versus Cellular

A

First layer(s) deposited/Formed after acellular layer(s)
At least one layer over entire root with
many layers near cervical one-third/
Layered over acellular, mostly in apical
one-third, especially in interradicular
region
Formed at slower rate/ Formed at faster rate
No embedded cementocytes/ Embedded cementocytes
Width constant over time/ Can widen over time; layers can be added

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11
Q

Intermediate Cementum

A
  • It is the first cementum deposited
    on the root’s surface
  • It is formed by the inner epithelial
    root sheath cells that formed
    during root dentin formation
  • This deposition occurs before the
    root sheath cell layer disintegrates
  • It is situated between the granular
    dentin layer of Tomes and the
    secondary cementum
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12
Q

Acellular Afibrillar Cementum

A

Coronal Cementum
No cells or fibres
Thickness 1-15

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13
Q

Acellular Extrinsic- fiber cementum

A

covers cervical third to half of the root surface
no cells contains sharpey fibres
thickness 30 and 230

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14
Q

Cellular intrinsic-fiber cementum

A

fills resorption lacunae
contains cells but no sharpey fibres

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15
Q

Cellular Mixed, Startified cementum

A
  • covers apical portions of root surface and functions
  • contains cells, intrinsic fibres and sharpey fibers
    -thickness 100 and 1000
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16
Q

Incremental lines of salter

A

Cementum is deposited rhythmically,
resulting in unevenly spaced incremental
lines (of Salter).
* In acellular cementum, these lines tend
to be close together, thin and even.
* In the more rapidly formed cellular
cementum, the lines are further apart,
thicker and more irregular.
* They are hyper mineralised areas with
less collagen and more ground substance

17
Q

Cemento-Enamel Junction (CEJ)

A
  • Overlap- Cementum overlapping the
    enamel (60%)
  • Meet- End-to-end relationship of
    enamel and cementum (30%)
  • Gap- Space between the enamel and
    the cementum with the
    dentin (D) exposed (10%)
18
Q

Age Changes of Cementum

A
  • With ageing, the relatively smooth
    surface of cementum becomes more
    irregular
  • Cementum resorption is one
    characteristic of ageing cementum
  • Cementum resorption may be caused
    by local or systemic factors, or it may
    occur without apparent etiology
  • Cementum resorption is not
    necessarily continuous and may
    alternate with periods of repair and
    the deposition of new cementumdemarcated by reversal line
19
Q

Cementicles

A
  • They are mineralized spherical bodies of
    cementum found either attached to the
    cemental root surface or lying free in the
    PDL
  • The origin of a cementicle may be a nidus
    of epithelial cells.
  • They form from the appositional growth of
    cementum around cellular debris in the PDL
  • They are more prevalent along the root in
    an ageing person, although they may also
    be found at a site of trauma.
20
Q

Hypercementosis

A
  • It is the excessive production of
    cellular cementum
  • It mostly occurs at the apex or
    apices of the tooth and also
    the inter radicular region of
    molars
  • It may be present on
    radiographs as a radiopaque
    (or lighter) mass at each root
    apex

SKA (5 decks)

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