CSA histology of enamel and dentine caries

Question 1

What is enamel like?

Answer 1

• brittle so relies on dentine for resistance

Question 2

What is enamel pure mineral like?

Answer 2

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

Question 3

Where is enamel most thick?

Answer 3

incisal edge

Question 4

What are HAP crystals ordered in ?

Answer 4

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

-Approx. 5um in diameter

Question 5

What are prisms like in longitudinal sections?

Answer 5

perp. to ADJ

Question 6

What is enamel production like?

Answer 6

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

Question 7

What are Striae of Retzius (brown incremental lines)

Answer 7

superimposed on 5um periodicity

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

Question 8

When are tuft proteins seen?

Answer 8

enamel crown = completely removed with acid (demineralised)

Question 9

What is tuft protein ?

Answer 9

areas in between prisms where enamel proteins collected

Question 10

When are tufts seen

Answer 10

transverse section

Question 11

what are prisms in tufts like

Answer 11

• Prisms = change path at each level

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

Question 12

What are spindles?

Answer 12

odontoblast process crossing forming ADJ into developing enamel during crown development

Question 13

Where do spindles originate ? ( cigar shape)

Answer 13

at ADJ into enamel

Question 14

What are seen in longitudinal sections?

Answer 14

• 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

Question 15

What are striae of retzius?

Answer 15

Incremental growth lines = obliquely across prisms to

approach enamel surface

Question 16

What are striae of retzius associated with at surface?

Answer 16

depressions called Perikymata

Question 17

What does scalloping of ADJ do ?

Answer 17

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

Question 18

What are enamel spindles?

Answer 18

• Continuous w/ dentinal tubules across ADJ

Question 19

What are enamel spindles due to ?

Answer 19

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

Question 20

What is gnarled enamel ?

Answer 20

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

Question 21

What does gnarled enamel look like ?

Answer 21

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

Question 22

What are cross striations?

Answer 22

Represent daily incremental growth lines + give prisms ladder appearance

Question 23

What are HS bands?

Answer 23

Optical effects due to longitudinal sectioning of alternating paths of prisms

Question 24

Where are HS bands only visible?

Answer 24

inner 2/3rds of enamel

Question 25

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

Answer 25

parallel

Question 26

What is Aprismatic Enamel?

Answer 26

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

Question 27

What is white spot lesion?

Answer 27

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

Question 28

Is fissure lesion smaller than white spot lesion?

Answer 28

yes

Question 29

What is translucent zone?

Answer 29

Approx. 1% of mineral = lost

Question 30

What is dark zone?

Answer 30

-Some remin. = occurred here | Diff. range of sizes = causes light scattering so get dark

Question 31

What is surface zone ?

Answer 31

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

Question 32

What are dentinal tubules

Answer 32

•Channels run from pulp to outer dentine

Question 33

What do dentinal tubules contain ?

Answer 33

fluid and odontoblasts (form/maintain dentine)

Question 34

What do tubules follow?

Answer 34

S shapes paths (primary cirvature) | - get secondary curvatures superimposed onto S shape

Question 35

when are tubules branched

Answer 35

at ADJ

Question 36

What is interglobular dentine ?

Answer 36

incomplete fusion of calcospherites) with mineralising front as dentine

Question 37

What are calcospherites ?

Answer 37

islands of mineralising dentine)

Question 38

what does incomplete fusion do ?

Answer 38

traps poorly mineralised dentine matrix = arched shape

Question 39

What is dentine divided into ?

Answer 39

primary or 2nd dentine

Question 40

what is in coronal dentine ?

Answer 40

mantle and circumpulpal dentine

Question 41

When is mantle dentine formed?

Answer 41

first + laid adjacent to ADJ

Question 42

What are collagen fibres arranged in mantel dentine ?

Answer 42

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

Question 43

When is primary dentine laid down?

Answer 43

give tooth overall shape

Question 44

When is secondary dentine laid down

Answer 44

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

Question 45

What are dead tracts?

Answer 45

NO fluid, cell process, mineral deposits - Fill with debris during sectioning process - produces black appearance

Question 46

what are layers of pulp/dentine interface?

Answer 46

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)

Question 47

Where is pre dentine layer?

Answer 47

present between odontoblast layer and advancing mineralised front of mineralised dentine

Question 48

What are odontoblasts responsible for?

Answer 48

forming and maintaining dentine

Question 49

What do odontoblasts secrete initially?

Answer 49

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

Question 50

What does Odont. layer contain?

Answer 50

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

Question 51

What is cell free zone?

Answer 51

beneath odont. layer

Question 52

What does cell rich zone?

Answer 52

contains  conc. of cell nuclei

Question 53

What is body of pulp made up of?

Answer 53

loose connective tissue - Fibroblast = main cell type - Macrophages - Undifferentiated mesenchyme - incr. nerves/capillaries here = supply o.layer and pulp itself:

Question 54

Where is undifferentiated mesenchyme ?

Answer 54

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

Question 55

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

Answer 55

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

Question 56

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

Answer 56

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

Question 57

What is sclerotic/translucent dentine ?

Answer 57

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

Question 58

When does sclerotic/translucent dentine occur?

Answer 58

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

Question 59

What is dead tract/

Answer 59

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

Question 60

When is reparative dentine produced ?

Answer 60

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

Question 61

What is reactionary dentine ?

Answer 61

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