Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BDS2 BAMS > Enamel Morphology > Flashcards

Enamel Morphology Flashcards

1
Q

physical characteristics of enamel

A
  • hardest tissue in the body
  • resists abrasion
  • brittle
  • supported by dentine
  • covers tooth crown
  • varies in thickness
  • translucent
  • transparency increases with mineralisation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why does enamel need to be supported by dentine?

A

in order for enamel to act properly

if unsupported becomes too brittle and fails

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the shape of dentine tubules?

A

S shape (sinusoidal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

which class of teeth has thinner enamel?

A

decidous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is enamel thickness mainly based upon?

A 
function
(worn enamel at tip of incisor because of tooth wear, deciduous teeth have thinner enamel as less time in oral cavity)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

enamel regional variations

A
  • surface enamel more mineralised and harder than deeper enamel
  • hardness decreases from cusp tip/incisal edge to cervical region

have functional and clinical significance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

where is enamel is more mineralised?

A

surface enamel more mineralised and harder than deeper enamel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the basic unit of enamel?

A

enamel rod/prism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the dimensions of an enamel rod?

A

5um x 2.5 mm

length of enamel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

where to rods run from?

A

ADJ to surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how are rods arranged?

A

enamel rods orientation varies within and along rod

  • some crystallites are parallel and some perpendicular
  • some have inclination
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what dictates the arrangement of the rod?

A

crystallite orientation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what causes cross striations in enamel?

A

daily growth

  • see long parallel rods
  • approx. 4um
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what caused brown transverse striae in enamel?

A

weekly intervals of growth

- 25-35um apart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why do we use acid etch on enamel?

A

make enamel structure more gripping, increase in Surface area - makes more uneven

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what basic shape are enamel rods?

A

key hole

- with head and tail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are enamel rods composed of mainly?

A

crystallite (hydroxyapatite)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

SEM is

A

scan electron microscopy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

breakdown of enamel content

A 
hydroxyapatite
- 95% weight (90% volume)
water
- 4% weight (5-10% volume)
organic matrix 
- 1% weight (1-2% volume)

in healthy enamel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what proteins are in the organic matrix of enamel?

A

amelogenins
enamelins
peptides
amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what causes the changes in weight and volume % for HA, water and organic matrix?

A

density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what happens to composition of enamel after restoration?

A

changes - lose water and organic matrix

significant change for the ability of enamel to withstand forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is in dentine but not in enamel?

A

collagen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

why does enamel require organic component?

A

to withstand forces
- nanomechanical properties

otherwise too brittle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

when is crystallite orientation determined?

A

during enamel formation

- the matrix itself established lay out of crystallites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how are crystallites deposited in relation to ameloblast membrane?

A

at right angles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what other process also influences crystallite orientation?

A

tommes process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what are the 2 stages in enamel maturation?

A

mineralisation at first stage is approx. 30%

need break down of amelogenins

crystal can then grow to full potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what condition occurs if no breakdown of amelogenins?

A

amelogenins imperfecta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is supersaturation?

A

proteins in enamel matrix allow hypersaturation of Ca and PO4 in a very specific arrangement, that creates the perfect form for crystallite formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

hydroxyapatite formula

A

Ca10(PO4)6(OH)2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what shape are hydroxyapatite crystals?

A

hexagonal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

dimensions of HA crystals

A

70nm x 25nm x up 1um long

not all the way through rod

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what ions can be substituted into HA

A

Mg2+
CO3 (2-)
F-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

when is carbonated apatite more common? CO3 (2-)

A

when tooth erupting, as enamel matures carbonated apatite decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

ground sections contain

A

minerals (no soft tissue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

decalcified sections contain

A

soft tissues only (no mineral)

38
Q

enamel rods shape characteristics

A
  • run in sinusoidal shape
  • adjacent groups of rods have different orientations
  • periodic orientation causes banding patterns (Hunter-Schreger bands; not parallel)
39
Q

what causes Hunter-Schreger bands in enamel?

A

periodic orientation in enamel rods

  • not parallel
  • absent in outer enamel
40
Q

what is gnarled enamel?

A
  • optical effect at cusps

- greater concentration of rods in cusps regions as distribution of forces requires it

41
Q

what are 2 types of incremental lines you can see in enamel?

A
  • brown striae of Retzius

- Perikymata

42
Q

what is a neonatal line?

A

particular band of incremental growth lines

- Consequence in changes in diet and physiological changes at birth

43
Q

what are perikymata?

A

incremental growth lines that appear on the surface of tooth enamel as a series of linear grooves.
- Can disappear over time due to abrasion

44
Q

what are enamel tufts?

A

hypominerlised regions due to residual matrix protein at prism boundaries

  • at ADJ
  • can see projection into rods
45
Q

what are enamel lamella?

A

incomplete maturation of groups of prisms

  • ‘fault’ line extending through enamel thickness
  • goes all the way into rods unlike tufts
46
Q

what are enamel spindles?

A

odontoblasts process extending into enamel

  • projections are clearer, like fingers
  • odontoblasts leave projections there after early stage - rare
47
Q

what can you not see in a ground section?

A

any cells or organic materials

48
Q

where is enamel thinnest?

A

cervical region where it usually tapers gradually

49
Q

where is enamel thickest?

A

at the incisal edge or under the cusp.

In the absence of any tooth wear, the enamel is around 2 mm thick.
The exact amount will vary between different teeth.

50
Q

what are the set of lines in enamel that run at right angles to the enamel surface and ADJ?

A

enamel prisms/rods

alternating light and dark lines

Another set lie almost parallel to the outer surface and are broader

51
Q

what are the brown striae of Retzius?

A

Thicker brownish lines that run obliquely from outer surface to the EDJ

external representation is perikymatas
- lines on tooth surface

52
Q

where can you see evidence of scalloped ADJ?

A

below cuspal edges and incisal edges, compared with the side of the crown

53
Q

advantages of scalloping in ADJ

A

Advantage as be able to withstand high shearing forces

  • More mechanical retention against strong occlusal forces between enamel and dentine
  • Shearing forces less at cervical region of the tooth as scalloping less
54
Q

why can you get abfraction at cervical portion of tooth?

A

lose portion of enamel,

does need caries, needs external shearing forces and enamel detaches from dentine (occlusal lesions)

  • Reduced density of enamel and reduction of scallops
  • Usually on upper premolars

Bending forces on teeth – like flex ruler almost

55
Q

what do cross striations indicate?

A

daily growth of tissue

0.004mm (4um) apart

56
Q

where is the thickest enamel on posterior teeth?

A

Enamel is thickest under the cusps.

In the absence of any tooth wear, the enamel is around 2.5 mm thick.

57
Q

how do enamel prisms lie and run?

A

prisms lie perpendicular to the EDJ

run from EDJ to the tooth surface

58
Q

do the enamel prisms extend to the outer surface of enamel?

A

No. The outer 20-70 μm of enamel has no prisms (aprismatic enamel), where crystallites lie parallel to each other.

59
Q

prism orientation in regards to cavity prepartions

A

important

want to be perpendicular to ADJ cut so no unsupported enamel (will be brittle and break off, no resistance to occlusal forces)

Enamel is inherently brittle and can fracture along the prism boundaries.
- supported by dentine is less likely to fracture.

When a tooth is prepared for a restoration, it is essential to make sure that there is no unsupported enamel, especially at the cavity margins.

60
Q

advantages of gnarled enamel cusps

A

Give more resilience to the enamel on top of it to withstand occlusal forces
- Hence why under cups tips

61
Q

why are dentinal tubules closer together at pulp?

A

Odontoblast start ADJ and go inwards to pulp

  • Come closer together
  • Don’t increase in number (if die, stem cells will replace them)
62
Q

where is the good dentine to bond to?

A

at the ADJ outskirts – more to bond as more intertubular space
- Large cavity harder to bond to

More moisture towards pulp as tubules closer together – adversely affect resin bonds (also spaces between tubules advantages for etch
- Increased tag spaces – good for chemical retention

63
Q

what happens to tubules SA as they migrate?

A

occupy a smaller surface area as they migrate in hence, they are wider at the periphery

Smaller diameter and wider apart at ADJ
Closer together and wider diameter at pulp

64
Q

where is dentine formation?

A

inside the tubules

- intratubular dentine

65
Q

pits and fissure caries

A

base wider at EDJ and top of pyramid at exterior of tooth

  • when invades dentine - pyramid reversed (base at ADJ and tip at deeper part of lesion/ towards the pulp) 2 pyramids back to back

can have fissure in palatal surface of tooth

66
Q

smooth surface caries

A

lesion will have base towards the exterior (reverse of enamel lesion of pits & fissures)

enamel that is not fully supported by dentine common especially trying to Hall technique

67
Q

how can a fissure increase the tooth’s susceptibility to caries?(3)

A
  • The fissure is difficult to clean, and becomes a plaque trap.
  • There is reduced thickness of enamel at the base of the fissure, so a carious lesion can spread rapidly into dentine.
  • A fissure will reduce access of salivary buffering to the deeper regions of the dental plaque and make cleansing by brushing more difficult
68
Q

implication on dental practice on the orientation of prisms

A

spatial arrangement of prisms may provide some resilience so that the enamel ‘gives’ very slightly during application of occlusal loads

69
Q

how to differentiate between enamel lamella and artefacts?

A

lamella will stay when demineralised whereas artefact will disappear

Artefacts would not be embedded onto the general structure of the tooth.

70
Q

enamel spindle

A

spindles are thought to be formed by odontoblast processes that extend for a short distance into the Internal Enamel Epithelium layer of the enamel organ from the ADJ. – round corner (projection of odontoblast)

71
Q

gnarled enamel is…

A

When enamel rods/prisms intertwine, complex arrangement

72
Q

enamel tuft

A

represent regions of incompletely (hypomiineralised) mineralised enamel matrix.

Tufts extend a short distance from the ADJ, and resemble tufts of grass.
Failed production of enamel structure

73
Q

enamel lamellae

A

represent regions of incompletely mineralised enamel matrix. Lamellae extend through the full thickness of enamel.

74
Q

dead tracts

A

Black coloured dentinal tubules under transmitted light– air filled

The tubules are empty and are sealed at the pulpal end by the deposition of tertiary dentine.

Tertiary dentine is laid down in response to wear of the overlying enamel and dentine. (What types of ‘wear’ might be involved?)

75
Q

primary dentine

A

refers to dentine laid down while the tooth is forming. It is completed when the root apex is fully formed.

76
Q

secondary dentine

A

dentine is laid down during the life of the tooth, after the tooth is fully formed.

77
Q

how to find the boundary between primary and secondary dentine?

A

Often, it is difficult to see the boundary between primary and secondary dentine, but sometimes there is a change in orientation/direction of the dentinal tubules. (not always seen)

78
Q

tertiary dentine

A

laid down as a result to insult to the tooth

79
Q

dentinal tubules permeabilty

A

increase with depth

size of tubules accomodated permeability
- deeper the cavity the larger need for cavity lining

80
Q

can tertiary dentine have dead tracts?

A

no
- missing tubules

Makes sense as forms a plug against irritants that are trying to invade

Made by odontoblast or recruited stem cells (to make dentine as dead/damaged odontoblasts)

  • Reactionary – primary odontoblasts
  • Reparative – recruited stem cells
81
Q

reactionary tertiary dentine is made by

A

primary odontoblasts

82
Q

reparative tertiary dentine is made by

A

recruited stem cells

83
Q

inner and outer dentine tubule density comparison

A

Inner dentine has higher density and outer dentine has smaller diameter tubules

84
Q

what is the change in orientation of tubules nearer the pulp mark?

A

This marks the onset of secondary dentine formation.

if there is a substantial amount of secondary dentine, suggests that the tooth has been in function for several decades

85
Q

why can the apex of a tooth be wider when the tooth erupts?

A

tooth not fully formed yet

86
Q

rate of secondary dentine formation compared to primary dentine

A

slower

87
Q

predentine is

A

unmineralised

Pale pink stained zone at pulpal aspect of dentine

88
Q

describe tubules at the dentine pulpal interface

A

Tubules come closer together nearer the pulp because the surface area of the pulp-dentine interface is less than that of the original ADJ.

So the odontoblasts are forced together, as more dentine is laid down.

The result is that the odontoblast cell layer has a pseudostratified appearance.

89
Q

calcospherites

A

Darker red ‘blobs’ in the predentine (pale pink staining tissue) represent centres of minerlisation (calcification)

90
Q

structures in the inner part of dentine

A

an odontoblast process

unmyelinated nerve terminal (especially in dentine under the cusps),

perhaps also the process of a dendritic cell (an antigen presenting cell).

91
Q

structures in the outer part of dentine

A

no vital cells

BDS2 BAMS (54 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions