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OCB02 > Dentin > Flashcards

Dentin Flashcards

1
Q

Which substance gives teeth their yellow colour?

A

Dentin

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2
Q

What is the composition of dentin by weight and volume?

A

Inorganic - 70% w, 50% v

Organic - 20% w, 30% v

Water - 10% w, 20% v

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3
Q

Describe the inorganic component of dentin.

A

Primarily hexagonal hydroxyapatite prisms found on or between collagen fibrils

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4
Q

What are the dimensions of the hydroxyapatite prisms in dentin?

A

10x35x100nm

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5
Q

Describe the organic component of dentin.

A

90% type I collagen (large diameter - 100nm) and traces of type III and V

8% non-collagenous proteins

2% lipids

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6
Q

Which direction does pulpal pressure push dentinal fluid?

A

Outwards

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7
Q

Why is the water component in dentin important practically?

A

Problem for binding composites which are hydrophobic

Limits penetration by bonding agents

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8
Q

What is the primary curvature in dentin?

A

Curved sigmoid course of dentinal tubules/odontoblasts from enamel to pulp

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9
Q

What is the secondary curvature in dentin?

A

Odontoblasts changing direction every few microns (diurnal)

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10
Q

What are the contour lines of Owen?

A

In dentin, when the diurnal changes in direction of odontoblasts line up

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11
Q

How can you spot mantle dentin?

A

Marked branching seen just below EDJ in coronal dentin

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12
Q

What is the mantle dentin equivalent in the root?

A

Granular layer of Tomes

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13
Q

What is contained in a dentin tubule? (4)

A

Odontoblast process and smaller ones

Dentinal fluid

Processes of antigen-presenting cells

Sensory nerve terminal fibres

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14
Q

Where is peritubular space not found?

A

Predentin

Most recently mineralised dentin

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15
Q

Where are the processes of antigen-presenting cells and sensory nerve terminal fibres usually found?

A

Beneath cusps in dentinal tubules

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16
Q

How do the sensory nerve terminal fibres in dentin detect stimuli?

A

Hydraulic movement of dentinal fluid within the tubule

17
Q

What is another name of intratubular dentin?

A

Peritubular dentin

18
Q

Is intratubular dentin mostly primary or secondary dentin?

A

Secondary (fills up tubules)

19
Q

In the root, what does intratubular dentin give rise to?

A

Translucent dentin

20
Q

How does the mineral content of intratubular dentin compare to intertubular dentin?

A

Hypercalcified - 15% more mineralised

21
Q

What substances make up the organic non-collagenous matrix intratubular dentin? (6)

A

Glycoproteins

Proteoglycans

Lipids

Osteonectin

Osteocalcin

Bone sialoprotein

22
Q

How does the acid etch used on dentin compare to that used on enamel and why?

A

Weaker

Less mineralised than enamel

23
Q

What is the smear layer?

A

Debris layer, 15-20um thick, produced when friction occurs

24
Q

Why do we use acid etch before bonding?

A

Acid removes mineral to expose collagen fibrils (nm) and removes smear layer

Resin can penetrate at um and nm levels to create a strong bond

25
Q

What are von Ebner’s lines?

A

Light and dark paired bands in dentin perpendicular to tubules, 2-4um apart

Optical effect formed due to circadian variation in acid-base balance

26
Q

What are Andresen lines?

A

Long period variations in odontoblast secretion, visibly enhanced by polarised light

27
Q

What causes the neonatal line?

A

Birth (slows movement of odontoblasts)

28
Q

What is translucent dentin?

A

Fills dentin tubules as a response to an external stimulus

29
Q

What is translucent dentin often referred to and why is this not correct?

A

“Sclerotic” - implies abnormal hardening but hardness depends on structure, not just mineralisation

30
Q

How does translucent dentin differ from peritubular dentin?

A

Mineral is crystalline, plate-like β-octacalcium phosphate not hydroxyapatite

31
Q

What is another name for β-octacalcium phosphate?

A

Whitlockite

32
Q

What are dead tracts?

A

Empty tubules sealed at pulpal end by tertiary dentin

33
Q

Why do dead tracts appear dark in ground section?

A

Air cannot enter

34
Q

Why is the granular layer of Tomes less mineralised compared to circumpulpal dentin?

A

Branching and looping tubules

Interglobular dentin

35
Q

What is the orientation of the collagen fibres in the granular layer of Tomes?

A

Parallel to root surface

OCB02 (19 decks)

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