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BDS3 DMS > Dental Ceramics (Christy) > Flashcards

Dental Ceramics (Christy) Flashcards

1
Q

Is all porcelain ceramic?

A

yes, all porcelain is ceramic

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2
Q

Are all ceramics porcelain?

A

no, all ceramics are not porcelain

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3
Q

What is kaolin?

A

kaolin is a clay

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4
Q

Kaolin is hydrated X silicate

A

X - aluminium

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5
Q

Is kaolin opaque?

A

yes, kaolin is opaque

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6
Q

Dental ceramics need to be X so kaolin is removed and feldspar and silica replace it

A

X - translucent

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7
Q

What are the components of dental ceramics?

A

dental ceramics:

<5% = kaolin

12-25% = quartz (silica)

70-80% = feldspar

1% = metal oxides

up to 15% = glass

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8
Q

What is the main difference between decorative and dental ceramics?

A

the main difference between dental and decorative ceramics is the amount of feldspar

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9
Q

What does feldspar act as?

A

felddspar acts as a flux

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10
Q

What lowers the fusion and softening temperature of the glass?

A

feldspar lowers the fusion and softening temperature of glass

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11
Q

What is the lowest fusing component of dental ceramics and flows during firing, forming a solid mass around the other components?

A

feldspar is the lowest fusing component and flows during firing, forming a solid mass around the other components

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12
Q

What conveys colour to the ceramic?

A

metal oxides convey colour to the ceramic

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13
Q

What are conventional dental ceramics supplied as?

A

conventional dental ceramics are supplied as powder

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14
Q

How is the conventional dental ceramic powder made?

A

conventional dental ceramic powder is made by:

  • heating the constituents to a high temperature (>1000°C)
  • cooling rapidly (fritting)
    • cooled in water creating cracks and crazing of the ceramic mass
  • mill the frit to a fine powder
  • add binder, which is often starch
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15
Q

What do feldspathic ceramics form when heated to 1150-1500°C?

A

when heated to 1150-1500°C, feldspathic ceramics form leucite

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16
Q

What is leucite?

A

leucite is potassium aluminium silicate

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17
Q

Fabrication of a crown:

  • ceramic powder is mixed with X and applied to the die with a brush
  • the crown is built up using different porcelains for dentine and enamel
    • these are not tooth coloured
  • the crown is heated in a furnace to coalesce the powder into ceramic
  • heating leads to sintering, which occurs just above the glass transition temperature
    • it is when the ceramic particles begin to fuse into a single mass
  • during sintering, the glass phase softens and will coalesce
  • over time there is controlled diffusion and a solid ceramic mass is formed
A

X - water

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18
Q

Fabrication of a crown:

  • ceramic powder is mixed with water and applied to the die with a brush
  • the crown is built up using different X for dentine and enamel
    • these are not tooth coloured
  • the crown is heated in a furnace to coalesce the powder into ceramic
  • heating leads to sintering, which occurs just above the glass transition temperature
    • it is when the ceramic particles begin to fuse into a single mass
  • during sintering, the glass phase softens and will coalesce
  • over time there is controlled diffusion and a solid ceramic mass is formed
A

X - porcelains

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19
Q

Fabrication of a crown:

  • ceramic powder is mixed with water and applied to the die with a brush
  • the crown is built up using different porcelains for dentine and enamel
    • these are not tooth coloured
  • the crown is heated in a furnace to X the powder into ceramic
  • heating leads to sintering, which occurs just above the glass transition temperature
    • it is when the ceramic particles begin to fuse into a single mass
  • during sintering, the glass phase softens and will coalesce
  • over time there is controlled diffusion and a solid ceramic mass is formed
A

X - coalesce

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20
Q

Fabrication of a crown:

  • ceramic powder is mixed with water and applied to the die with a brush
  • the crown is built up using different porcelains for dentine and enamel
    • these are not tooth coloured
  • the crown is heated in a furnace to coalesce the powder into ceramic
  • heating leads to X, which occurs just above the glass transition temperature
    • it is when the ceramic particles begin to fuse into a single mass
  • during sintering, the glass phase softens and will coalesce
  • over time there is controlled diffusion and a solid ceramic mass is formed
A

X - sintering

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21
Q

Fabrication of a crown:

  • ceramic powder is mixed with water and applied to the die with a brush
  • the crown is built up using different porcelains for dentine and enamel
    • these are not tooth coloured
  • the crown is heated in a furnace to coalesce the powder into ceramic
  • heating leads to sintering, which occurs just above the glass transition temperature
    • it is when the X particles begin to fuse into a single mass
  • during sintering, the glass phase softens and will coalesce
  • over time there is controlled diffusion and a solid ceramic mass is formed
A

X - ceramic

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22
Q

Fabrication of a crown:

  • ceramic powder is mixed with water and applied to the die with a brush
  • the crown is built up using different porcelains for dentine and enamel
    • these are not tooth coloured
  • the crown is heated in a furnace to coalesce the powder into ceramic
  • heating leads to sintering, which occurs just above the glass transition temperature
    • it is when the ceramic particles begin to fuse into a single mass
  • during sintering, the glass phase X and will coalesce
  • over time there is controlled diffusion and a solid ceramic mass is formed
A

X - softens

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23
Q

During sintering, how much does the material contract?

A

during sintering, the material contracts by about 20%

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24
Q

What dental restorative materials have the best aesthetics?

A

ceramics have the best aesthetic properties of any dental restorative material

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25
Q

Ceramics retain their surface X than other materials

A

X - better

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26
Q

Ceramics have X staining long term

A

X - less

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27
Q

What is it known as when light is allowed to pass through a material unchanged?

A

when light is able to pass through a material, this material is known as transparency

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28
Q

What is it known as when a material allows only some light to pass through (light changes direction as it passes through)?

A

a material is translucent when it allows some light to pass through (light changes direction as it passes through)

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29
Q

Are conventional dental ceramics chemically stable?

A

yes, conventional dental ceramics are chemically stable

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30
Q

Conventional dental ceramics are generally X by the wide pH range found in the mouth

A

X - unaffected

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31
Q

Do conventional dental ceramics take up stain from food/drink?

A

no, conventional dental ceramics do not take up stain from food/drink

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32
Q

Conventional dental ceramics have good X as there are minimal adverse effects on biologcial tissues

A

X - biocompatibility

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33
Q

What is the thermal expansion coefficient of conventional dental ceramics similar to?

A

the thermal expansion coefficient of conventional dental ceramics is similar to dentine

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34
Q

What can be said about the thermal diffusivity of conventional dental ceramics?

A

conventional dental ceramics have a low thermal diffusivity

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35
Q

Once fully fired, are conventional dental ceramics stable?

A

yes, once fully fired conventional dental ceramics are very stable

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36
Q

During the fabrication of conventional dental ceramics, what is a problem?

A

during the fabrication of conventional dental ceramics, shrinkage is a problem

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37
Q

Conventional dental ceramics have a X compressive strength

A

X - high

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38
Q

Conventional dental ceramics have a X hardness

A

X - high

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39
Q

Conventional dental ceramics have a high hardness, what can this lead to?

A

conventional dental ceramics have a high hardness, this can lead to abrasion of the opposing teeth - especially if they are not glazed

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40
Q

Conventional dental ceramics have a very X tensile strength

A

X - low

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41
Q

Conventional dental ceramics have a very X flexural strength

A

X - low

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42
Q

Conventional dental ceramics have a very X fracture toughness

A

X - low

43
Q

There is a time dependent X in strength in conventional dental ceramics, even in the absence of any applied force

A

X - decrease

44
Q

There is a time dependent decrease in strength of conventional dental ceramics, even in the absence of any applied load. What is this probably due to?

A

there is a time dependent decrease in strength of conventioanl dental ceramics, even in the absence of any applied load. This is probably due to the hydrolysis of Si-O groups within the material, over time in an aqueous environment

45
Q

Where can fractures initiate in conventional dental ceramics?

A

fractures can initiate in conventional dental ceramics at surface micro-cracks

46
Q

Where can conventional feldspathic ceramics be used?

A

conventional feldspathic ceramics can only be used in low stress areas

47
Q

Are conventional feldspathic crowns used as anterior or posterior crowns?

A

conventional feldspathic crowns are used as anterior crowns

48
Q

The aesthetics of conventional ceramics are good but they need to be X

A

X - stronger

49
Q

What are ways that the problems of conventional ceramics are overcome?

A

overcoming the problems with conventional ceramics:

  • produce a strong coping that is resistant to fracture and cover this with the conventional porcelain
  • cast or press a block of harder ceramic
  • mill a laboratory prepared block of ceramic
50
Q

What are examples of the different types of cores used for putting porcelain over?

A

strong copings:

  • alumina core
  • zirconia core
51
Q

What is used as a core material in porcelain jacket crowns?

A

alumina is used as a core material in porcelain jacket crowns

52
Q

What do alumina particles in alumina cores prevent?

A

alumina particles in alumina cores prevent cracks propagating

53
Q

Aluminous porcelain is X and can only be used as a core material

A

X - opaque

54
Q

What type of core was used as the first choice crown for anterior teeth for decades and is not strong enough for posterior use?

A

an alumina core was used as the first choice crown for anterior teeth for decades and is not strong enough for posterior use

55
Q

Is specialist equipment needed to create an alumina core?

A

no, specialist equipment is not required to make an alumina core - just a furnace

56
Q

Increased alumina content X the strength of the alumina core

A

X - increases

57
Q

What is the name of the alumina core technique where the core material has an alumina content of around 85%?

A

In-ceram is the technique when the core material has an alumina content of around 85%

58
Q

What is the name of the complicated technique (from in-ceram) being described?:

  • the ceramic core is formed onto a refractory model
  • a fine slurry of alumina is applied to the model
  • it is heated to 1120°C for 10 hours
  • this is below the glass transition temperature for alumina
  • partial sintering occurs
  • a porous core is produced
  • the core is infiltrated with lanthanum glass at 1100°C
A

slip casting:

  • the ceramic core is formed onto a refractory model
  • a fine slurry of alumina is applied to the model
  • it is heated to 1120°C for 10 hours
  • this is below the glass transition temperature for alumina
  • partial sintering occurs
  • a porous core is produced
  • the core is infiltrated with lanthanum glass at 1100°C
59
Q

In-ceram-spinel has X (Mg2O4) rather than alumina as its core material

A

X - spinel

60
Q

In-ceram-spinel has better X but lower flex strength

A

X - aesthetics

61
Q

What is the name of the technique which creates a pure alumina core that is >99% pure?

A

Procera creates a pure alumina core which is >99% pure

62
Q

What region are In-Ceram and Procera core types suitable for?

A

In-Ceram and Procera core types are suitable for single posterior crowns

63
Q

Are In-Ceram or Procera crowns used as a bridge material?

A

no, In-Ceram and Procera cores are not often used as a bridge material

64
Q

What is probably the most popular ceramic core material?

A

zirconia is probably the most popular ceramic core material

65
Q

What can be said about the hardness of zirconia?

A

zirconia is very hard

66
Q

Zirconia powder does not sinter unless heated to over X°C

A

X - 1600

67
Q

What is the zirconia used in dentistry?

A

the zirconia used in dentistry is yttria-stabilised zirconia

68
Q

Pure zirconia can X on cooling

A

X - crack

69
Q

Normal zirconia is a X crystal at room temperature

A

X - monoclinic

70
Q

Yttria is a X crystal structure

A

X - tetragonal

71
Q

If a crack begins in zirconia when the stress at the crack tip reaches a critical level, the crystal structure transforms to the X structure. This causes a slight expansion of the material and closes up the crack tip

A

X - monoclinic

72
Q

If a crack begins in yttira-stabilised zirconia when the stress at the crack tip reaches a critical level, the crystal structure transforms to the monooclinic structure. This causes a slight X of the material and closes up the crack tip

A

X - expansion

73
Q

If a crack begins in yttria-stabilised zirconia when the stress at the crack tip reaches a critical level, the crystal structure transforms to the monoclinic structure. This causes a slight expansion of the material and closes up the crack tip. What properties does this ability give the material?

A

If a crack begins in yttria-stabilised zirconia when the stress at the crack tip reaches a critical level, the crystal structure transforms to the monoclinic structure. This causes a slight expansion of the material and closes up the crack tip. This give a material which is very:

  • hard
  • strong (1000MPa flexural strength)
  • tough
74
Q

Is yttria-stabilised zirconia strong enough to be used as a brdieg framework?

A

yes, yttria-stabilised zirconia is strong enough to be used as a bridge framework

75
Q

Fabrication of a Zirconia core:

  • impression is taken of the preparation and sent to the lab
  • a model is cast and then scanned digitially
  • the software unit creates a bridge substructure on virtual preparations
  • minimum thicknesses of connectors are determined and fabricated
  • raw zirconia block is selected for X
  • the cut framework is then heat treated at around 850°C to achieve its final physical properties
    • this causes a 20% shrinkage but the computer software deals with this during the milling process
  • the framework is stained to an appropriate colour
  • zirconia core is then veneered with feldspathic porcelain to produce the final restoration
A

X - milling

76
Q

Fabrication of a Zirconia core:

  • impression is taken of the preparation and sent to the lab
  • a model is cast and then scanned digitially
  • the software unit creates a bridge substructure on virtual preparations
  • minimum thicknesses of connectors are determined and fabricated
  • raw zirconia block is selected for milling
  • the cut framework is then heat treated at around X°C to achieve its final physical properties
    • this causes a 20% shrinkage but the computer software deals with this during the milling process
  • the framework is stained to an appropriate colour
  • zirconia core is then veneered with feldspathic porcelain to produce the final restoration
A

X - 850

77
Q

Fabrication of a Zirconia core:

  • impression is taken of the preparation and sent to the lab
  • a model is cast and then scanned digitially
  • the software unit creates a bridge substructure on virtual preparations
  • minimum thicknesses of connectors are determined and fabricated
  • raw zirconia block is selected for milling
  • the cut framework is then heat treated at around 850°C to achieve its final physical properties
    • this causes a X% shrinkage but the computer software deals with this during the milling process
  • the framework is stained to an appropriate colour
  • zirconia core is then veneered with feldspathic porcelain to produce the final restoration
A

X - 20

78
Q

Fabrication of a Zirconia core:

  • impression is taken of the preparation and sent to the lab
  • a model is cast and then scanned digitially
  • the software unit creates a bridge substructure on virtual preparations
  • minimum thicknesses of connectors are determined and fabricated
  • raw zirconia block is selected for milling
  • the cut framework is then heat treated at around 850°C to achieve its final physical properties
    • this causes a 20% shrinkage but the computer software deals with this during the milling process
  • the framework is X to an appropriate colour
  • zirconia core is then veneered with feldspathic porcelain to produce the final restoration
A

X - stained

79
Q

Fabrication of a Zirconia core:

  • impression is taken of the preparation and sent to the lab
  • a model is cast and then scanned digitially
  • the software unit creates a bridge substructure on virtual preparations
  • minimum thicknesses of connectors are determined and fabricated
  • raw zirconia block is selected for milling
  • the cut framework is then heat treated at around 850°C to achieve its final physical properties
    • this causes a 20% shrinkage but the computer software deals with this during the milling process
  • the framework is stained to an appropriate colour
  • zirconia core is then veneered with X porcelain to produce the final restoration
A

X - feldspathic

80
Q

What can be said about the cost of the equipment needed for fabricating zirconia cored crowns?

A

expensive equipment is required for zirconia cored crowns

81
Q

With zirconia cored crowns, there is the potential for the veneering porcelain to X from the core

A

X - debond

82
Q

Can you etch or bond zirconia cored crowns?

A

no, you cannot etch or bond zirconia cored crowns

83
Q

What can be said about the fit of zirconia cored crowns?

A

the fit of zirconia cored crowns is generally excellent

84
Q

Whta are the different materials that can be used for milled core crowns and bridges?

A

milled core crowns and bridges:

  • zirconia
  • lithium disilicate
  • precious metal
  • non-precious metal
  • titanium
85
Q

Ceramics all have a surface X layer for best aesthetics

A

X - sintered

86
Q

For the same material, a milled crown will be X than a built up or pressed crown

A

X - stronger

87
Q

Fabrication of a milled crown:

  • impression and cast taken in the normal way
  • cast model up in the normal way
  • cast goes into X
  • scanned image of the cast available
  • opposing cast is scanned and articulated
  • crown margin selected
  • crown margin adjusted
  • crown type selected and placed on “model”
  • size and shape of the selected crown is adjusted
  • save file
  • send to milling machine
A

X - scanner

88
Q

Fabrication of a milled crown:

  • impression and cast taken in the normal way
  • cast model up in the normal way
  • cast goes into scanner
  • scanned image of the cast available
  • X cast is scanned and articulated
  • crown margin selected
  • crown margin adjusted
  • crown type selected and placed on “model”
  • size and shape of the selected crown is adjusted
  • save file
  • send to milling machine
A

X - opposing

89
Q

Fabrication of a milled crown:

  • impression and cast taken in the normal way
  • cast model up in the normal way
  • cast goes into scanner
  • scanned image of the cast available
  • opposing cast is scanned and articulated
  • crown margin selected
  • crown margin adjusted
  • X selected and placed on “model”
  • size and shape of the selected crown is adjusted
  • save file
  • send to milling machine
A

X - crown type

90
Q

Cast and pressed ceramics:

  • restoration is waxed-up as you would for a metal restoration
  • X
  • cast from a heated ingot of ceramic (1100°C)
  • no sintering occurs, the ceramic ingot is already fully condensed prior to firing
  • once devested and cleaned, the restoration is heated to improve its crystal structure - producign crack inhibiting crystals
    • this is known as ceraming
  • the cast crown can be stained
  • more often it is cut back labially and veneered with appropriate feldspathic porcelains
A

X - invested

91
Q

Cast and pressed ceramics:

  • restoration is waxed-up as you would for a metal restoration
  • invested
  • cast from a heated ingot of ceramic (X°C)
  • no sintering occurs, the ceramic ingot is already fully condensed prior to firing
  • once devested and cleaned, the restoration is heated to improve its crystal structure - producing crack inhibiting crystals
  • this is known as ceraming
  • the cast crown can be stained
  • more often it is cut back labially and veneered with appropriate feldspathic porcelains
A

X - 1100

92
Q

Cast and pressed ceramics:

  • restoration is waxed-up as you would for a metal restoration
  • invested
  • cast from a heated ingot of ceramic (1100°C)
  • no X occurs, the ceramic ingot is already fully condensed prior to firing
  • once devested and cleaned, the restoration is heated to improve its crystal structure - producing crack inhibiting crystals
    • this is known as ceraming
  • the cast crown can be stained
  • more often it is cut back labially and veneered with appropriate feldspathic porcelains
A

X - sintering

93
Q

Cast and pressed ceramics:

  • restoration is waxed-up as you would for a metal restoration
  • invested
  • cast from a heated ingot of ceramic (1100°C)
  • no sintering occurs, the ceramic ingot is already fully condensed prior to firing
  • once devested and cleaned, the restoration is heated to improve its X structure - producing crack inhibiting crystals
    • this is known as ceraming
  • the cast crown can be stained
  • more often it is cut back labially and veneered with appropriate feldspathic porcelains
A

X - crystal

94
Q

Cast and pressed ceramics:

  • restoration is waxed-up as you would for a metal restoration
  • invested
  • cast from a heated ingot of ceramic (1100°C)
  • no sintering occurs, the ceramic ingot is already fully condensed prior to firing
  • once devested and cleaned, the restoration is heated to improve its crystal structure - producing crack inhibiting crystals
    • this is known as X
  • the cast crown can be stained
  • more often it is cut back labially and veneered with appropriate feldspathic porcelains
A

X - ceraming

95
Q

Cast and pressed ceramics:

  • restoration is waxed-up as you would for a metal restoration
  • invested
  • cast from a heated ingot of ceramic (1100°C)
  • no sintering occurs, the ceramic ingot is already fully condensed prior to firing
  • once devested and cleaned, the restoration is heated to improve its crystal structure - producing crack inhibiting crystals
    • this is known as ceraming
  • the cast crown can be stained
  • more often it is cut back X and veneered with appropriate feldspathic porcelains
A

X - labially

96
Q

What is the ceramic used in cast and pressed ceramic processes?

A

the ceramic used in cast and pressed ceramics:

  • lithium disilicate glass
  • leucite reinforced glass
97
Q

Ceraming is a X stage process

A

X - 2

98
Q

What are the 2 stages of ceraming?

A

ceraming:

  1. crystal formation where the maximum number of crystal nuclei are formed
  2. crystal growth to maximise the physical properties
99
Q

For cast and pressed ceramics, strong materials have X crystal size and high volume fraction of crystals

A

X - small

100
Q

For cast and pressed ceramics, strong materials have small crystal size and X volume fraction of crystals

A

X - high

101
Q

Lithium disilicate glasses have unique X-like crystals

A

X - needle

102
Q

Lithium disilicate glasses have unique needle-like crystals, which makes crack propagation through this material very difficult - giving X flexural strength

A

X - good/high

103
Q

Any silica containing ceramic can be etched with X to produce a retentive surface

A

X - hydrofluoric acid

BDS3 DMS (10 decks)

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