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BDS2 - oral biology > periodontium > Flashcards

periodontium Flashcards

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1
Q

what is periodontium

A

tissue surrounding and supporting teeth

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2
Q

what is the role of the periodontium

A
  • retains tooth in the socket
  • resists masticatory loads
  • is a defensive barrier, protecting tissues against threats from the oral environment
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3
Q

what is junctional epithelium

A

the physical barrier separating the body tissues from the oral environment
*protects against microorganisms - every drop of saliva has 10^6 micro-organisms

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4
Q

what is the epithelial attachment

A

what you are trying to make healthy

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5
Q

what is the difference between gingival disease and periodontal disease

A

difference is established by the space between the gingiva and the tooth - sulcus/pocket

  • periodontal disease is commonly pockets beyond 3mm
  • periodontal disease common in older patients
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6
Q

what is cementum

A
  • covers root dentine
  • anchor for periodontal fibres
  • similar in structure to bone - has collagen matrix and lamellar arrangement like lamellar bone
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7
Q

what are the 2 types of cementum

A
  • cellular - has cementocytes and cells have projections

* acellular - no cells or very few cells

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8
Q

what is cementum laid down by

A

cementocytes

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9
Q

what are the characteristics of acellular cementum

A
  • no or few cells within
  • usually adjacent to dentine
  • first formed (primary cementum)
  • also called EXTRINSIC FIBRE CEMENTUM
  • has collagen fibres from the periodontal ligament - these are called Sharpay’s fibres
  • present on cervical 2/3 of root
  • is acellular because there is no need for metabolic activity
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10
Q

what are the characteristics of cellular cementum

A
  • contains cementocytes
  • later formed (secondary cementum)
  • present on apical part of root and in furcation regions
  • no Sharpay’s fibres - when treating furcations the restorations are more likely to fail as less fibres
  • also called INTRINSIC FIBRE CEMENTUM
  • intrinsic collagen fibres run parallel to the surface
  • has no role in tooth attachment
  • may represent a transitional form
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11
Q

how does the type of cementum affect the treatment

A

depends whether cellular or acellular cementum - treatment will vary
*can sometimes get areas where the two types overlap each other

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12
Q

does cementum help overcome toothwear

A

Yes.

Cementum helps overcome toothwear which is overcome by eruption so need cementum in these areas

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13
Q

what does alveolar bone do

A
  • provides attachment for periodontal ligament fibres
  • very important for transferring forces across bone as it would break without cushioning
  • supports the teeth
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14
Q

what is the structure of alveolar bone

A
  • similar to bone elsewhere in the body
  • ‘cortical plate’ forms inner lining of tooth socket
  • penetrated by nutrient canals - VOLKMANNS canals
  • has inner ‘cancellous’ bone (spongy), containing marrow
  • inferior of tooth socket may have nutrient foramina perforating the inner cortical bone - corresponds to lamina dura in radiographs
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15
Q

what happens when teeth are lost

A

the alveolar process is resorbed, leaving a residua ridge

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16
Q

how wide is periodontal ligament

A

approximately 0.2 mm

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17
Q

what is periodontal ligament

A

an organised, regular connective tissue

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18
Q

what makes up PDL

A
  • cells
  • extracellular matrix (ground substance)
  • fibres - run in specific direction, attach tooth to jaw
  • nerves
  • blood vessels
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19
Q

what is the structure and function of the matrix

A
  • contains hyaluronate GAGs (glycosaminoglycans)
  • glycoproteins - fibronectin
  • proteoglycans - proteodermatin sulphate and chondroitin/dermatan
  • behaves like a viscoelastic gel - wobbles like a jelly so allows it to spring back to original shape
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20
Q

what is the structure and function of the cells

A
  • fibroblasts - generate and maintain the structure
  • cementoblasts - same job as fibroblasts
  • osteoclasts and cementoclasts - destroy/resorb bone and cementum
  • epithelial cells - originate in the root, called cell rests (or debris) of Malassez - important in pathological implications such as cysts
  • defence cells - important in periodontal disease - link to the autoimmune response
21
Q

what nerves are there in the periodontal ligament

A

sensory and autonomic (sympathetic)

22
Q

what is the sensory nerves responsible for

A
  • mechanoreceptors (A delta and A beta fibres)
  • can be rapidly or slowly adapting
  • control chewing through proprioception - automatically changes the way you eat different thing - can be problem with dentures as no PDL
  • nociceptors (A delta and C fibres)
  • protective reflexes
  • inhibit jaw elevator motor neurons
  • A fibres are myelinated, C fibres are not
23
Q

what are the autonomic nerves responsible for

A

*blood vessel control - vasoconstriction

24
Q

why do we need to have adrenaline in LA

A

for vasoconstriction - need to constrict to reduce the clearance of LA from area so procedure can be longer
*but with PDL, don’t want reduced blood flow so need to do some procedures without adrenaline

25
Q

what is the blood supply

A
  • from inferior and superior alveolar arteries, passing into PDL from the alveolar bone
  • from lingual and palatine arteries, supplying the gingiva
26
Q

what is the role of the fibres

A

transmit biting forces to the alveolar bone

27
Q

what are true PDL fibres

A

fibres connecting the tooth to the bone at or apiece to the alveolar crest

28
Q

what are the ‘gingival’ ligament

A

fibres mainly above the alveolar crest, including ‘free gingival’ fibres

29
Q

what collagen types make up the fibres

A

type I and type III

30
Q

what do the collagen fibres do

A

these are principal fibres (true PDL)

  • support the tooth in load bearing
  • some disease can affect the collagen
31
Q

what are ozytalan fibres

A

present in human PDL

  • have some consequences in periodontal disease development
  • function is uncertain
32
Q

what fibres are absent in humans but present in animal

A

elastic fibres

33
Q

what are the 6 main principal fibre groups

A
  • alveolar crest
  • horizontal
  • oblique
  • apical
  • interradicular
  • transeptal
34
Q

what 5 principal fibres are in the alveoli-dental ligament

A
  • alveolar crest
  • horizontal
  • oblique
  • apical
  • interradicular
35
Q

what principal fibre group is in the inter-dental ligament

A

transeptal

36
Q

what does the alveolar crest fibres do

A

stretch to bring the tooth up / \

37
Q

what does the horizontal fibres do

A

associated with rotation -

38
Q

what does the oblique fibres do

A

stretch and transform tooth force to bone \ //

39
Q

what teeth is the interradicular fibres associated with

A

multi-rooted teeth

40
Q

what do transeptal fibres do

A

these are not connected to bone

*goes between cementum of adjacent teeth

41
Q

want do gingival fibre groups do

A

support the free gingiva

42
Q

where are gingival fibres located

A 
in the lamina propria in the marginal gingiva 
*dento-gingiva
*alveolo-gingiva
*dento-periosteal
*circular
these all go around the tooth
43
Q

why must you pull the lips out when taking impression

A

so that the alveolar mucosa will create a margin that creates the mucogingival line/junction
*do not want to invade the alveolar mucosa

44
Q

what is the dent-gingival junction

A
  • contain junctional epithelium
  • has an enamel cuticle
  • crevicular epithelium is located here (oral sulcular)
45
Q

why is junctional epithelium and epithelial attachment important

A

connects epithelium to enamel
*has special arrangement of cells - has basale on each side (internal and external) which allows attachment between enamel and lamina propria

46
Q

what is interdental col

A

the region between two teeth that is protected by the contact point - is non-keratinised as it doesn’t have loading forces

47
Q

what forces is PDL mainly subjected to

A

intrusive forces

  • mastication
  • swallowing
  • speech
  • parafunctions (clenching, grinding)
48
Q

what are the extrusive forces teeth are subjected to

A

*sticky foods
*orthodontic forces
(although rarely subjected to these forces)

49
Q

what is PDL loading process

A
  • application of brief forces
  • measure tooth movements
  • loads applied to tooth pushes it into the socket
  • initial elastic component pushes it in
  • later viscous creep brings it back into place (has viscoelastic properties)
  • there is tension in the PDL fibres
  • the ECF is compressed when pushed in

BDS2 - oral biology (5 decks)

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