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enamel and dental caries Flashcards

to outline the mechanism of underlying progression of enamel and dentine to examine the microstructure of both enamel and dentine and how it affects the carious process to draw comparison between two tissues to outline the physiocochemical process by which caries cause destruction to outline the pulp-dentine complex and how it provides a limited defence mechanism to examine the structure of a typical tooth surface enamel caries lesion and an occlusal pit lesion

1
Q

what is the definition of dental caries

A

it is a localised, chemical dissolution of the tooth surface bought about by metabolic activity in a microbial deposit coving the tooth surface at any given time

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2
Q

what is the dental caries promoted and maintained by

A

by frequently dietary supply of fermentable carbs

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3
Q

where can dental caries attack

A

pits
fissures
grooves
especially during eruption and approximate surfaces

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4
Q

what is the percentage of mineral component of the tissue by weight

A

95%

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5
Q

where is the mineral content the highest

A

highest at the surface and decreases as it reaches the ADJ

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6
Q

what is the water content in volume in enamel

A

10%

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7
Q

what is the water content in volume in dentine

A

20%

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8
Q

what is the residual content by weight in enamel of water

A

3%

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9
Q

what is the residual content by weight in dentine of water

A

10%

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10
Q

what is the residual content by weight in enamel of protein

A

1%

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11
Q

what is the residual content by weight in dentine of protein

A

20%

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12
Q

what are the crystal dimensions in enamel (w x t)

A

68 x 26nm

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13
Q

what are the crystal dimensions in dentine ( w x t)

A

35 x 10 nm

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14
Q

what is the length of the crystal in enamel

A

7mm

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15
Q

what is the crystal length in dentine

A

indeterminate

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16
Q

what are the physical properties of human enamel

A

highly mineralised
withstands shearing forces
abrasion resistance is high
BUT brittle

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17
Q

what happens with the loss of the dentine support

A

unsupported enamel can fracture resulting in cavitation

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18
Q

what happens to hardness of enamel as we move towards the ADJ

A

DECREASES

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19
Q

what happens to the density of the enamel as we move towards the ADJ

A

DECREASES

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20
Q

what re the physical properties of dentine

A

flexible

poor abrasion resistance

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21
Q

why is dentine flexible

A

due to its organic matrix and tubular architecture

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22
Q

how is enamel considered

A

it is considered as microporous

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23
Q

what is the structure of the outermost enamel

A

it is rather porous

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24
Q

what developmental features can be seen in the enamel microstructure

A

irregular tissues and micropores

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25
Q

what is the diameter of irregular tissues and mirco pores

A

0.5-1.5micro metres

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26
Q

the irregular tissues and micropores can take part in

A

diffusion processes

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27
Q

what to the striae of retzius and perikymata act as

A

larger diffusion pathways

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28
Q

what is the crystals separated by in the enamel microstructure

A

tiny inter-crystalline spaces filled with water and organic materials

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29
Q

how can we clinically tell that enamel is microporous

A

the teeth start to dry out and become lighter in colour therefore shade check at the start

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30
Q

where does acid penetrate more readily

A

where there is greater porosity

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31
Q

what type of crystals do acid dissolution occur

A

irregular crystal outlines although demineralisation and destruction in the prism core is also seen

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32
Q

where does caries progress more rapidly

A

prism boundaries
cross striations
striae of retzius

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33
Q

how many cervical dentinal tubules are in the dentine cross section

A

10-25000 tubules per mm2

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34
Q

how many superficial tubules are found in the cross section of dentine

A

10-25000 tubules per mm2

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35
Q

what is the diameter of superficial tubules

A

0.5-1.2 microns in diameter

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36
Q

how many deep dentinal tubules are there in the cross section of dentine

A

30-52000 tubules per mm2

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37
Q

what is the diameters of the deep dentinal tubules

A

1-3 microns in diameter

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38
Q

what do the middle of the dentinal tubules contain

A

they contain odontoblasts and a small amount of extracellular dentinal fluid

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39
Q

how much % of the dentine volume do the superficial dentinal tubules occupy

A

approx 1 %

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40
Q

how much % of the deeper dentine volume do the superficial dentinal tubules occupy

A

30%

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41
Q

is the deeper dentine more porous and permeable to bacteria chemicals than superficial dentine

A

YES

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42
Q

what is the chemical equation that can be used to represent the reaction which takes place when enamel mineral dissolves

A

Ca10(PO4)6(OH)2 ⇌ 10Ca2+ + 6PO43– + 2OH–

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43
Q

what happens under suitable conditions

A

the biofilm can shift ecologically to become cariogenic so it produces a low pH

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44
Q

clinically what do the lesions look like as they first appear

A

opaque white spots- and the tooth needs to be dry with 3-in-1

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45
Q

why does the carious lesion appear white

A

because the sub surface enamel has become porous as a result of dissolution by acid

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46
Q

why does the carious lesion turn Brown

A

due to the fact the lesion might take up stain and may end up exposing dentine

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47
Q

what shape is the lesion shown on an x ray

A

a wedge shaped lesion

48
Q

what is the pore volume of the surface zone

A

less than 5%

49
Q

what is the pore volume of the body of lesion

A

5-25%

50
Q

what is the pore volume of the dark zone

A

2-4%

51
Q

what is the pore volume of the translucent zone

A

1%

52
Q

what is the pore volume of the sound enamel

A

0.1%

53
Q

what is the mineral per unit volume loss of the surface zone

A

1-10%

54
Q

what is the mineral per unit volume loss of the body of the lesion

A

24%

55
Q

what is the mineral per unit volume loss of the dark zone

A

6%

56
Q

what is the section of enamel stained with to make the different zones visible

A

chloronaphthalene

57
Q

what is the translucent zone like

A

deepest and least area affected

58
Q

what is the body of the lesion like

A

most affected part and the greatest porosity

59
Q

what lies underneath the plaque

A

the intact surface zone

60
Q

what separates the body of the lesion and the translucent zone

A

the dark zone

61
Q

what is found in the translucent zone

A

small number of uniform sized pores.

62
Q

what do these small pores form in the translucent zone

A

produces the translucent optical effect which is seen in the lesion

63
Q

why does the dark zone look dark

A

it diffracts light due to unequal pore sizes and also due to high protein content in this zone

64
Q

why are there different size pores in the dark zone

A

due to the fact that some pores remineralise and some do not

65
Q

how much mineral loss does the body of the lesion have

A

greater than 20% and may have 60-70% before cavitation occurs

66
Q

what is now important in clinical settings

A

Preserving the integrity of the fragile surface zone enamel overlying the lesion

67
Q

which minerals are needed to remineralise the tooth surface

A

CALCIUM AND PHOSPHORUS which diffuse into the porous zone

68
Q

where are dentine HA crystals found

A

in an organic matrix of type 1 collagen

69
Q

what is dentine composed of

A

mineral and protein

70
Q

how many stage process is caries in dentine

A

three stages

71
Q

what’s the first stage of caries in dentine

A

mineral is removed by the bacterial acid

72
Q

what is the second stage of caries in dentine

A

then the ground substance by enzymes( including 8% component of the organic matrix; the non-collagenous proteins NCPs

73
Q

what is the third stage of caries in dentine

A

enzymatic removal of collagen

74
Q

where do bioactive molecules migrate

A

down the dentinal tubules and stimulate tertiary formation and the other purple reparative processes

75
Q

what are the dimensions of the intertubular dentine

A

5nm x 35 nm x 100 nm ( length and width

76
Q

what minerals do intertubular dentine

A

less calcium and more carbonate

77
Q

how is peritubular dentine different than intertubular dentine

A

lacking a collagenous fibrous matrix
5-12% more mineralised than intertubular dentine
laid down as a physiological response to ageing
less soluble

78
Q

how does the initial plural response to caries activated

A

by bacterial acids and their cell wall components such as lipopolysaccharides

79
Q

what does the dental pulp complex react to

A

irritation

inflammation and the promotion of mineralisation

80
Q

what do odontoblasts produce beneath the area of challenge

A

tertiary dentine

81
Q

what are defence mechanisms produced by

A

odontoblasts or their replacement cells from progenitor cells within the pulp tissue

82
Q

describe tertiary dentine

A

All hard tissue deposited on the pulpal surface in response to an external stimulus. It is restricted to the region beneath the irritation and provides a barrier to the progress of caries and toxins.

83
Q

describe reactionary dentine

A

dentine forming in response to milder irritation in which, although some damage is sustained and some odontoblasts die
this dentine has an irregular appearance with fewer tubules than circumpulpal dentine

84
Q

what does reparative dentine describe

A

dentine formed in response to stronger stimuli in which the odontoblasts in the region have destroyed and the calcified tissue has been formed by newly differentiated by odontoblast like cells.
much more irregular than circumpulpal dentine
if the pulp is exposed this can cause pulp exposed healing by reparative dentine forming a mineralised bridge

85
Q

describe sclerotic dentine

A

when dentinal tubules fill in a response to external stimulus such as slow caries or beneath severe attrition
it appears translucent

86
Q

what happens as the inflammatory response moves towards the pulp

A

intensifies

87
Q

what happens if there is irreversible inflammation of the pulp

A

loss of vitality

bacterial colonisation of the pulp by proteolytic gram -ve facultative anaerobic bacteria

88
Q

How do smooth surface caries spread into dentine

A

In five stages which are called
Plaque layer forms on the enamel due to the fact that sugar+ time + fermentable carbohydrates
Stage 2: acid dissolution occurs on enamel prisms and loss of the mineral and increases the porosity allows acid attack
Stage 3: spreads laterally along the EDJ
stage 4: dentinal tubules increase in volume as sclerotic dentine is deposited and reactionary dentine
Stage 5: enamel surface caries plaque bacteria invade the lesion and penetrate dentinal tubules

89
Q

What is found in deep fissures and pits

A

Food debris and dental plaque

90
Q

Where does the various lesion form

A

Starts at both sides of the fissure wall NOT at the base

The one shaped lesion moves perpendicularly toward the ADJ - precede cavitation and occur without apparent break

91
Q

What are occult caries

A

The spread of the lesion which can reveal a large hidden dentine lesion below the smaller enamel lesion

92
Q

Why do occult caries form

A

Due to the enamel having a high fluoride conc

93
Q

Why do we restore mildly symptomatic or asymptomatic teeth

A

To restore the function and aesthetics
Maximise the longevity of the tooth restoration complex by removing soft dentine to place a durable restoration
Protect the pulp dentine complex and arrest the lesion activity

94
Q

What is the ICCC

A

The international caries consensus collaboration

95
Q

How can we clinically test for sound dentine

A

Scratching sound when scraping with dental probe

96
Q

What are the clinical characteristics for soft dentine

A

Deforms with pressure and can be easily scooped with the excavator tool
It is described as caries inffected dentine and appears moist

97
Q

What are the clinical characteristics of leathery dentine

A

Does not deform when pressure is applied to it with a excavators probe
Often described as caries affected dentine

98
Q

What are the clinical characteristics of firm dentine

A

Physically resistant to hand excavation and requires a lot of pressure to lift it

99
Q

What are the clinical characteristics of hard dentine(sound dentine)

A

A scratchy sound cAn be heard when a probe is taken across

100
Q

What are the three layers of a deep various lesion. Into dentine

A

Infected dentine
Affected dentine
Sound dentine

101
Q

What is the infected dentine consist of

A

Most coronal layer
There is gross disruption of the organic fibrillation matrix of the dentine so that it is not recognisable as possessing dentinal tubules, peritubular or inter tubular dentine

102
Q

In the infected dentine stage what are the proteolytic bacteria using as food source

A

Collage type 1

103
Q

What are the characteristics of the caries affected dentine

A

Recognisable dentine structure but starting to be damaged by the wave of demineralisation
Slightly softer than normal dentine

104
Q

Is shown in the normal dentine structure

A

There will be evidence of the dentinal tubules reducing in size due to the fact that odontoblasts are laying down sclerotic dentine
As the caries gets deeper the layer of the pulp becomes more thin so there is a greater risk of direct pulpit exposure

105
Q

How can the depth of the carious lesion be estimated

A

Using a bite wing radiograph

106
Q

How can deep caries be defined

A

As radiography
If evidence of the carious lesion reaching the inner third or inner quarter of dentine but still with a well defined zone of radio opaque dentine separating the dentine from the pulp

107
Q

How is extremely deep caries defined as

A

Radiographic evidence of caries penetrating the entire thickness of the dentine without a radio opaque zone of dentine separating it from the pulp

108
Q

How do we manage non Selective removal to hard dentine

A

Complete caries removal
Only hard sound dentine remains so that demineralised dentine is completely removed
This is OVER TREATMENT

109
Q

How do we manage selective removal to firm dentine

A

Leaves leathery dentine pulpally- resistance feeling in the hand excavator

110
Q

What is the treatment for shallow or moderately deep cavitation lesions

A

Selective removal of firm dentine

111
Q

Explain the treatment of selective removal to soft dentine

A

Recommended in deep cavitation lesions- extending into pulpal third or quarter of the dentine
Soft carious dentine left at the top of the pulp

112
Q

What is stepwise excavation

A

This involves carious tissue removal in two stages

The first one some soft carious tissue is left over the pulp

113
Q

Why do we selectively remove soft dentine

A

A number of biological reactions underpin this approach:

  1. The two defence reactions of tubular mineralization and tertiary dentine reduce the permeability of the dentine, walling off the pulp from the bacteria invading the dentine in the lesion.
  2. Once a restoration is placed that seals the cavity, any remaining bacteria either die or change to reflect a non-cariogenic flora and the lesion will arrest.
  3. Note that the residual demineralised (affected) dentine may remineralise to some extent but will appear as a radiolucency under the new restoration on future radiographs so inform the patient and document this in your clinic outcome.
  4. Teeth treated this way require carful monitoring for possible failures such as continuing caries activity and may not be advisable under full coverage restorations which would obscure radiographic and clinical evaluation.
114
Q

What does a caries first look like

A

Soft discoloured and wet tissue

115
Q

What does the active deep carious environment become

A

Darker harder and drier appearance

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