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Craniofacial and Tooth Biology > 28. Histology of Perio, Gingiva and Oral Mucosa > Flashcards

28. Histology of Perio, Gingiva and Oral Mucosa Flashcards

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1
Q

Compare and describe pattern of cementum distribution at different parts of the root and how this relates to age?

A
  • normally in young people, slowly formed acellular cementum predominates the root as teeth have been exposed to comparably less mechanical stress than in older people
  • in older people, occlusal wear and compensatory tooth movement induced formation of thicker layer of fast forming cellular cementum especially at apical and interradicular regions
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2
Q

What is the significance of cementum not meeting enamel at CEJ?

A
  • in 10% of cases
  • get exposure of root dentine
  • patients have a higher risk of dentine sensitivity and root caries
  • especially where gingiva recedes
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3
Q

Why are cementocytes shaped peculiarly?

A
  • long cellular processes creating small canals (canaliculi) in cementum
  • cellular processes/canaliculi are interconnected and directed towards periodontal ligament from which cementocytes get their nutrients
  • cementum is avascular with no blood vessels
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4
Q

What do Lines of Salter represent?

A

periodic activity of cementocytes
- i.e pauses in cementum deposition

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5
Q

What do Sharpey’s fibres do?

A
  • collagen fibres that insert into cementum and bone
  • become mineralised to anchor fibres of PDL in hard tissues
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6
Q

Differences in PDL between young and old patient

A
  • thicker in younger patients
  • contains more cells in younger (fibroblasts)
  • collagen fibre bundle in older people are thicker and tissue appears fibrotic
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7
Q

Function of oblique fibres in PDL

A
  • most abundant group
  • resist compressive forces i.e occlusal forces caused by mastication
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8
Q

What are the main types of collagen in PDL and functions?

A
  • type 1 (80%) and type 3 (15%)
  • type 1 forms majority of fibre bundles in PDL
  • type 3 forms reticular fibres that crosslink to form fine meshwork of collagen fibres implicated in supporting blood vessels when PDL compressed
  • type 3 interacts with platelets to form blood clots and important to wound healing
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9
Q

how do osteons form and how are they linked to osteocytes?

A
  • consist of central Haversian canal surrounded by concentric layers of lamellar bone
  • osteoblasts enter inside of them through blood vessel in Haversian canal and produce bone matrix later mineralised to bone
  • osteoblasts aligned along bone so results in formation of concentric layers of bone (lamellar bone)
  • when an osteoblasts gets trapped in bone, termed ‘osteocyte’
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10
Q

How are osteons different in adjacent region? Compare with with Sharpey’s fibres - what are these?

A
  • osteon is adjacent to bundle bone characterised by presence of Sharpey’s fibres
  • bundle bone always found near PDL as PDL fibres insert here and constantly remodel as part of normal physiology or in response to tooth movement
  • regions further away from PDL consist of lamellar bone that form majority of alveolar process
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11
Q

What is bone remodelling at reversal stage?

A
  • osteoclasts have stopped resorbing bone
  • have disappeared from region, leaving behind resorption bays termed ‘Howship’s lacunae’
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12
Q

Compare reversal line and resting line

A
  • reversal line is where a change from bone resorption to bone deposition had occurred, scalloped to show positions of Howship’s lacunae before bone deposition resumed
  • resting line caused by pauses in bone deposition. lines are straighter because osteoblasts align along existing bone
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13
Q

Keratinisation in gingival epithelium?

A
  • orthokeratinised in cats as functional adaptation to increased abrasion by tougher diet
  • in humans, gingiva mainly parakeratinised and only partially ortho (in areas of increased action)
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14
Q

Keratinisation of sulcular epithelium?

A
  • nonkeratinised
  • bounds the gingival sulcus and acts as epithelial barrier
  • development of correct depth of sulcus induced by masticatory forces acting on gingiva
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15
Q

Keratinisation in Nasmyth’s membrane?

A
  • epithelial tag composed of primary enamel cuticle and cell remnants of reduced enamel epithelium
  • primary enamel cuticle is internal basal lamina produced by REE cells and attached to enamel
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16
Q

Keratinisation of junctional epithelium

A
  • nonkeratinised
  • derived from REE that covers enamel of erupting tooth
  • REE/junctional ep cells attach tightly to enamel surface via primary enamel cuticle and hemidesmosomes
  • keratin would prevent this
17
Q

Which gingival fibres are associated with dento-gingival, alveo-gingival and transseptal fibres? Give function

A
  • dento-gingival and alveo-gingival fibres connect tooth and alveolar crest to lamina propria of free and attached propria
  • these strong fibres establish and maintain a tight association between gingiva and tooth
  • transseptal fibres form an interdental fibre system connecting all teeth of jaw - controls mesio-distal spacing of teeth
18
Q

Why is there no bleeding when a tooth erupts? Relate to forming of DGJ

A
  • fusion of REE of an erupting tooth with oral epithelium creates DGJ resulting in epithelial continuum
  • connective tissue including blood vessels are never exposed to oral cavity, therefore no bleeding
  • junctional epithelium remains tightly attached to enamel surface
19
Q

Surface cells of all epithelia are sloughed off. What happens to surface cells of junctional epithelium?

A
  • sloughed off/desquamated into gingival sulcus
  • become component of gingival crevicular fluid
20
Q

Describe effect of gingival inflammation of sulcular and junctional epithelium. Why?

A
  • inflammation has caused the sulcular and junctional epithelium to form long, irregular rete processes that project lamina propria (epithelial hyperplasia)
  • pathological response may compensate for loss of connective tissue mainly collagen
  • intercellular spaces between epithelial cells also become larger and basal lamina may be damaged allowing for easier penetration by microorganisms and toxins
21
Q

Describe effect of gingival inflammation on connective tissue. What’s the role of neutrophils, macrophages and lymphocytes?

A
  • area of inflammation characterised by lots of neutrophils, macrophages and lymphocytes
  • number of collagen fibres dramatically reduced compared to healthy gingiva
  • chronic inflam leads to destruction of gingival collagen fibres resulting in damage to gingiva and bleeding
  • during inflam, cytokine secretion e.g IL-6 and metalloproteinases/MMPs
  • MMPs normally involved in remodelling of connective tissue by degrading damaged collagen fibres that need to be renewed during subsequent wound repair of damaged tissue
  • however, in chronic, wound healing suppressed and continuous activity of MMPs results in excessive collagen degradation and increased tissue damage
  • for example, in chronic periodontitis, overproduction of MMP8 by neutrophils results in excessive degradation of collagen
22
Q

Examine gingival and palatal epithelium. What is their keratinisation status? Describe function of keratin here in monkeys

A
  • in monkeys, both orthokeratinised
  • much thicker keratinised layer in palatal epithelium than in humans
  • functional adaptation to consumption of tougher food such as fibrous plants
  • keratinised layer of oral epithelia to resist abrasion caused by masticatory forces
23
Q

What is the functional significance of folding in epithelial-connective tissue interface?

A
  • interdigitation of epithelial ridges (rete pegs) and papillae of lamina propria increases surface area and stability of epithelium-connective tissue interface
  • prevents separation of these two tissue layers, especially if exposed to masticatory forces
24
Q

Function of submucosa and hard palate
What cells do they contain to achieve function?

A
  • submucosa found in lateral/posterior regions of hard palate
  • consists of loose connective tissue (fibroblasts), adipose tissue (adipocytes), minor salivary glands and larger blood vessel and nerves
  • submucosa provides motility and acts as cushion in mucosae not directly exposed to masticatory forces e.g buccal mucosa
  • in contrast, gingiva forms a mucoperiosteum that provides stability and functions to withstand masticatory forces
  • in mucoperiosteum, highly fibrous lamina propria is directly attached to periosteum of bone
25
Q

Which type of collagen is predominant in mucosa of gingiva and palate and what properties does it provide?

A
  • collagen type 1
  • produces long strong fibres for tensile strength to resist shearing forces

Craniofacial and Tooth Biology (25 decks)

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