CSA histology of enamel and dentine caries Flashcards

1
Q

What is enamel like?

A
  • brittle so relies on dentine for resistance
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2
Q

What is enamel pure mineral like?

A

3% water, 1% protein (non-collagenous) and 96% HAP:

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3
Q

Where is enamel most thick?

A

incisal edge

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4
Q

What are HAP crystals ordered in ?

A

prism/rod runs from dentine (ADJ) to below tooth surface

-Approx. 5um in diameter

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5
Q

What are prisms like in longitudinal sections?

A

perp. to ADJ

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6
Q

What is enamel production like?

A

• Circadian rhythm in enamel production = , daily, cross-striations w/ 5um periodicity:

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7
Q

What are Striae of Retzius (brown incremental lines)

A

superimposed on 5um periodicity

o Towards cusp = irregularly spaced but more regular towards cervical margin

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8
Q

When are tuft proteins seen?

A

enamel crown = completely removed with acid (demineralised)

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9
Q

What is tuft protein ?

A

areas in between prisms where enamel proteins collected

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10
Q

When are tufts seen

A

transverse section

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11
Q

what are prisms in tufts like

A
  • Prisms = change path at each level

- High protein content at prism boundaries = superimposed on each level

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12
Q

What are spindles?

A

odontoblast process crossing forming ADJ into developing enamel during crown development

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13
Q

Where do spindles originate ? ( cigar shape)

A

at ADJ into enamel

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14
Q

What are seen in longitudinal sections?

A
  • Striae of Retzius
  • Enamel Spindles (also see in thick transverse sections)
  • Scalloped Nature of ADJ
  • Gnarled Enamel
  • Hunter-Schreger Bands
  • Cross Striations of Enamel Prisms
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15
Q

What are striae of retzius?

A

Incremental growth lines = obliquely across prisms to

approach enamel surface

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16
Q

What are striae of retzius associated with at surface?

A

depressions called Perikymata

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17
Q

What does scalloping of ADJ do ?

A

aids retention of enamel to dentine + resists shearing forces (more irregular + incr. SA at point of contact between enamel/dentine)

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18
Q

What are enamel spindles?

A
  • Continuous w/ dentinal tubules across ADJ
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19
Q

What are enamel spindles due to ?

A

odontoblast process crossing the forming ADJ into developing enamel during crown development which leaves a void

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20
Q

What is gnarled enamel ?

A

-Evolved to resist incr. loads and decr. shearing forces at cusps

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21
Q

What does gnarled enamel look like ?

A
  • On sides of crown, prisms run in straight lines perp. (90 to ADJ)
  • At cusp tip) prims = appear more disordered
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22
Q

What are cross striations?

A

Represent daily incremental growth lines + give prisms ladder appearance

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23
Q

What are HS bands?

A

Optical effects due to longitudinal sectioning of alternating paths of prisms

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24
Q

Where are HS bands only visible?

A

inner 2/3rds of enamel

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25
Q

What are prisms like in outer 1/3 of enamel?

A

parallel

26
Q

What is Aprismatic Enamel?

A

region under surface where prism not evident as crystals parallel to each other here

27
Q

What is white spot lesion?

A

translucent, dark,
surface and body of lesion
-Partial demin. >striae of Retzius/daily cross striations = appear more distinct

28
Q

Is fissure lesion smaller than white spot lesion?

A

yes

29
Q

What is translucent zone?

A

Approx. 1% of mineral = lost

30
Q

What is dark zone?

A

-Some remin. = occurred here

Diff. range of sizes = causes light scattering so get dark

31
Q

What is surface zone ?

A

intact zone, appears to be independent of F- conc.

32
Q

What are dentinal tubules

A

•Channels run from pulp to outer dentine

33
Q

What do dentinal tubules contain ?

A

fluid and odontoblasts (form/maintain dentine)

34
Q

What do tubules follow?

A

S shapes paths (primary cirvature)

- get secondary curvatures superimposed onto S shape

35
Q

when are tubules branched

A

at ADJ

36
Q

What is interglobular dentine ?

A

incomplete fusion of calcospherites) with mineralising front as dentine

37
Q

What are calcospherites ?

A

islands of mineralising dentine)

38
Q

what does incomplete fusion do ?

A

traps poorly mineralised dentine matrix = arched shape

39
Q

What is dentine divided into ?

A

primary or 2nd dentine

40
Q

what is in coronal dentine ?

A

mantle and circumpulpal dentine

41
Q

When is mantle dentine formed?

A

first + laid adjacent to ADJ

42
Q

What are collagen fibres arranged in mantel dentine ?

A

arranged perp. to ADJ + arise from sub-odontoblastic mesenchyme

43
Q

When is primary dentine laid down?

A

give tooth overall shape

44
Q

When is secondary dentine laid down

A

slower rate of dentine production at pulpal surface throughout tooth’s life

45
Q

What are dead tracts?

A

NO fluid, cell process, mineral deposits

  • Fill with debris during sectioning process
  • produces black appearance
46
Q

what are layers of pulp/dentine interface?

A
  1. Mineralised dentine
  2. Pre – dentine (unmineralised apart from calcospherites)
  3. Odontoblasts
  4. Cell Free Zone (of Weil)
  5. Cell Rich Zine
  6. Body of Pulp (loose, vascular and well innervated connective tissue)
47
Q

Where is pre dentine layer?

A

present between odontoblast layer and advancing mineralised front of mineralised dentine

48
Q

What are odontoblasts responsible for?

A

forming and maintaining dentine

49
Q

What do odontoblasts secrete initially?

A

collagenous matrix (pre – dentine) = subsequently mineralised (partly due to calcospherites fusion)

50
Q

What does Odont. layer contain?

A

incr. unmyelinated nerve fibres and capillary loops (arise from sub-odontoblastic plexus = includes cell free/cell rich zone and nerve plexus of Raschkow)

51
Q

What is cell free zone?

A

beneath odont. layer

52
Q

What does cell rich zone?

A

contains  conc. of cell nuclei

53
Q

What is body of pulp made up of?

A

loose connective tissue

  • Fibroblast = main cell type
  • Macrophages
  • Undifferentiated mesenchyme
  • incr. nerves/capillaries here = supply o.layer and pulp itself:
54
Q

Where is undifferentiated mesenchyme ?

A

present in sub-odontoblastic location = differentiates into cells to replace damaged odontoblasts

55
Q

how do nerves enter to supply Odont.layer and pulp?

A

through apical foramen
o incr. nerve ending between odontoblasts or within tubules
o incr. looped capillaries within o.layer

56
Q

does a lesion in dentine spread wider than lesion in enamel ?

A

YES , due to enamel prism arrangement around fissure + due to lateral spread at ADJ)

57
Q

What is sclerotic/translucent dentine ?

A

full occlusion of tubules by peritubular dentine laid down by o.process

58
Q

When does sclerotic/translucent dentine occur?

A

ageing process or defensive response to trauma (e.g. caries)

59
Q

What is dead tract/

A

Empty tubule left behind fills with air/debris during sectioning process appear black

60
Q

When is reparative dentine produced ?

A

surviving odontoblasts to seal dentinal tubules to prevent bacteria/toxins from directly causing damage to pulp

61
Q

What is reactionary dentine ?

A

If odontoblasts killed by rapid lesion then sub-odontoblastic cells seal tubules by producing non-tubular bone like material