Dentine - Ish'aaq Flashcards

1
Q

Describe the regional variation in dentinal tubules

A
  • Tubules are wider at the pulpal end as there’s more peritubular dentine on the wall at the crown end so smaller lumen
  • Tubules are widely seperated at coronal ends and more tightly packed near the pulp
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2
Q

Give 3 chemical properties of dentine

A
  • Smaller and shorter hydroxyapatite crystals than enamel but more impurities than enamel so mineral is more soluble in acid
  • Crystals are arranged along and inbetween collagen fibrils with the fibrils forming a meshwork
  • Dentine is a composite material, consisting of apatite crystals on an organic scaffold composed of collagen
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3
Q

Give 3 physical properties of dentine

A
  • Tubules are present, which are channels running from the pulp to the ADJ
  • Harder than bone + cementum, softer than enamel
  • Dentine is permable
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4
Q

How does the pulp help limit progress of chemicals and toxins, through the dentine, towards the pulp

A

Positive pressure from the pulp

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5
Q

How is peritubular dentine different to intertubular dentine

A
  • Peritubular dentine lacks collagen fibre matrix and consists of small crystals in a non-fibrillar matrix
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6
Q

Hows the strong bonding between acellular extrinsic cementum and dentine produced

A
  • Odontoblasts mineralise the first formed dentine layer and the first few micrometres of the fibrous fringe
  • Cementoblasts then secrete non-collagenous proteins which also strengthen the mineralisation
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7
Q

What are dentine tubules

A

Channels where the Tommes fibre can be found

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8
Q

What is intertubular dentine

A

The bulk of dentine and less mineralised than peritubular dentine

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9
Q

What is peritubular dentine

A

The ring directly around dentinal tubules and is where the odontoblasts deposit dentine

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10
Q

What are growth factors used for in dentine

A

Released during progress of dental caries to induce production of reparative dentine

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11
Q

What are lipids used for in dentine

A
  • Mineralisation as found on mineralisation front between collagen fibrils
  • Forms of phospholipids and cholesterol
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12
Q

What are proteoglycans important for

A

Collagen fibril assembly and cell mediated effects (cell adhesion, proliferation, differentiation)

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13
Q

When does interglobular dentine form

A
  • When dentine mineralisation is incomplete
  • Usually found in circumpulpal dentine
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14
Q

When does peritubular dentine form

A

When the Tommes fibre reaches its pre-determined length and moves towards pulp with odontoblasts

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15
Q

What happens to the dentine as the caries gets past the enamel and the ADJ

A
  • Carious lesion in dentine follows the path of the dentine tubules
  • Tubules make the dentine more permeable than enamel + allows for acid and plaque biofilm toxins to dissolve the hydroxyapatite and move towards the pulp
  • As there’s more impurities in dentine hydroxyapatite than enamel, its easier to dissolve
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16
Q

What are celospherites

A

Isolated islands of mineral deposited in the circumpulpal dentine

17
Q

Whats found inside the dentinal tubules

A
  • Ameloblastic processes present at the pulpal end and occupies the full width of tubules in developing dentine, but not seen in outer dentine
  • APCs from pulp and afferent sensory nerve axons
  • Dentinal fluid
18
Q

What is primary curvature

A
  • Overall shape of the dentinal tubules
  • Sinusoidal shape
19
Q

What is primary dentine (circumpulpal dentine)

A

Bulk of dentine in the root + crown which is uniform in structure except at the peripheral where interglobular dentine can be found

20
Q

Whats reactionary tertiary dentine

A

Dentine which forms in response to damage, when the damaged odontoblasts recover and continue to form dentine despite it being a little irregular with fewer tubules

21
Q

What is reparative tertiary dentine

A

A stimulus completely destroys original odontoblasts, new calcified tissue is found by newly differentiated odontoblast like cells

22
Q

What is secondary curvature in dentine

A

Smaller changes in direction of the tubules, they’re like little kinks in the tubules

23
Q

What is secondary dentine

A

Dentin formed from original odontoblasts. Once predetermined thickness of primary dentin has been reached, odontoblasts change direction and lay secondary dentine throughout life

24
Q

Whats tertiary dentine and how is it formed

A
  • Tertiary dentine is all hard tissue deposited on the pulpal surface in response to an external stimulus
  • Rapid progression of caries may mean sclerotic dentine can not form on outer dentine, so inserted tertiary dentine at pulpal end
25
Q

What are the 3 theories for how pain is felt in the dentine

A
  • Direct stimulation on nerves theory
  • Odontoblasts acting as receptors theory
  • Hydrodynamic theory - most likely mechanism
26
Q

What’s the ‘odontoblasts acting as receptors theory’ and what are the objections

A
  • Impulse travels down the odontoblastic process and into the odontoblast body and then transferred to nerve synapses and on to the plexus of raschkow
  • Odontoblastic processes don’t always extend to outer dentine and odontoblasts haven’t been shown to have synaptic junctions
27
Q

Whats the direct stimulation on nerves theory and what are the objections

A
  • Nerve extends from the plexus of raschkow right to end of dentinal tubules it can be acted on directly from external stimuli
  • Objections are theres no nerve axons in outer parts of dentine which is the most sensitive region
28
Q

Whats the hydrodynamic theory and what are the evidences

A
  • Effective stimulus applies to dentine triggers a flow of fluid within tubules which depolarise nerve endings and depolarisation is carried to plexus of raschkow
  • Evidences are that tubules are narrower at outer dentine so flow of fluid would be at a faster rate, leading to greater stimulus and increased sensitivity in that region
29
Q

Whats the granular layer

A

Found at the coronal end of dentinal tubules where Tommes fibre of odontoblast folds on itself

30
Q

What is the hyaline layer of hopwell smith

A
  • The most peripheral layer of dentine that forms directly under the CEJ
  • The final layer of dentine to mineralise
31
Q

Whats the main non-collagenous protein in dentine

A

Dentin phosphoprotein and dentine matrix protein 1 are both important in mineralisation

32
Q

Whats the role of mantle dentine and what is it

A
  • Help protect cracks, which have developed in the enamel from spreading into the dentine
  • First formed layer of dentine and closest layer to enamel
  • Slightly less mineralised than circumpulpal dentine displayed branching of tubules and its fibrils are perpendicular to the ADJ
33
Q

Whats translucent dentine and how does it differ from sclerotic

A
  • Translucent dentine partially allows light through as its formed as peritubular dentine colludes dentinal tubules from root apex and extends cervically and occurs due to age
  • Differs from sclerotic dentine due to disease and trauma, not age
  • Sclerotic is transparent not translucent
34
Q

Dentinal tubules follow the ‘s’ shape path of the odontoblasts. Where can you find branching of these tubules

A

Enamel-dentino junction

35
Q

Why is acid etching difficult on dentine

A

It remains damp due to a high organic and water content