Dental Ceramics (Christy) Flashcards by Fiona Rankin

Is all porcelain ceramic?

yes, all porcelain is ceramic

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Are all ceramics porcelain?

no, all ceramics are not porcelain

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What is kaolin?

kaolin is a clay

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Kaolin is hydrated X silicate

X - aluminium

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Is kaolin opaque?

yes, kaolin is opaque

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

X - translucent

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What are the components of dental ceramics?

dental ceramics:

<5% = kaolin

12-25% = quartz (silica)

70-80% = feldspar

1% = metal oxides

up to 15% = glass

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What is the main difference between decorative and dental ceramics?

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

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What does feldspar act as?

felddspar acts as a flux

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What lowers the fusion and softening temperature of the glass?

feldspar lowers the fusion and softening temperature of glass

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

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

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What conveys colour to the ceramic?

metal oxides convey colour to the ceramic

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What are conventional dental ceramics supplied as?

conventional dental ceramics are supplied as powder

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How is the conventional dental ceramic powder made?

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

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

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What is leucite?

leucite is potassium aluminium silicate

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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

X - water

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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

X - porcelains

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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

X - coalesce

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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

X - sintering

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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

X - ceramic

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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

X - softens

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During sintering, how much does the material contract?

during sintering, the material contracts by about 20%

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What dental restorative materials have the best aesthetics?

ceramics have the best aesthetic properties of any dental restorative material

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Ceramics retain their surface **X** than other materials

X - better

Ceramics have **X** staining long term

X - less

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

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

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

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

Are conventional dental ceramics chemically stable?

**yes**, conventional dental ceramics are chemically stable

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

X - unaffected

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

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

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

X - biocompatibility

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

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

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

conventional dental ceramics have a **low** thermal diffusivity

Once fully fired, are conventional dental ceramics stable?

**yes**, once fully fired conventional dental ceramics are very stable

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

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

Conventional dental ceramics have a **X** compressive strength

X - high

Conventional dental ceramics have a **X** hardness

X - high

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

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

Conventional dental ceramics have a very **X** tensile strength

X - low

Conventional dental ceramics have a very **X** flexural strength

X - low

Conventional dental ceramics have a very **X** fracture toughness

X - low

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

X - decrease

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?

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**

Where can fractures initiate in conventional dental ceramics?

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

Where can conventional feldspathic ceramics be used?

conventional feldspathic ceramics can only be used in **low stress areas**

Are conventional feldspathic crowns used as anterior or posterior crowns?

conventional feldspathic crowns are used as **anterior crowns**

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

X - stronger

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

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

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

strong copings: * **alumina** core * **zirconia** core

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

**alumina** is used as a core material in porcelain jacket crowns

What do alumina particles in alumina cores prevent?

alumina particles in alumina cores prevent cracks **propagating**

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

X - opaque

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

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

Is specialist equipment needed to create an alumina core?

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

Increased alumina content **X** the strength of the alumina core

X - increases

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

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

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

**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

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

X - spinel

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

X - aesthetics

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

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

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

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

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

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

What is probably the most popular ceramic core material?

**zirconia** is probably the most popular ceramic core material

What can be said about the hardness of zirconia?

zirconia is **very hard**

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

X - 1600

What is the zirconia used in dentistry?

the zirconia used in dentistry is **yttria-stabilised zirconia**

Pure zirconia can **X** on cooling

X - crack

Normal zirconia is a **X** crystal at room temperature

X - monoclinic

Yttria is a **X** crystal structure

X - tetragonal

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

X - monoclinic

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

X - expansion

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?

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

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

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

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

X - milling

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

X - 850

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

X - 20

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

X - stained

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

X - feldspathic

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

**expensive** equipment is required for zirconia cored crowns

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

X - debond

Can you etch or bond zirconia cored crowns?

**no**, you cannot etch or bond zirconia cored crowns

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

the fit of zirconia cored crowns is **generally excellent**

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

milled core crowns and bridges: * zirconia * lithium disilicate * precious metal * non-precious metal * titanium

Ceramics all have a surface **X** layer for best aesthetics

X - sintered

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

X - stronger

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

X - scanner

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

X - opposing

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

X - crown type

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

X - invested

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

X - 1100

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

X - sintering

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

X - crystal

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

X - ceraming

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

X - labially

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

the ceramic used in cast and pressed ceramics: * **lithium disilicate glass** * **leucite reinforced glass**

Ceraming is a **X** stage process

X - 2

What are the 2 stages of ceraming?

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

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

X - small

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

X - high

Lithium disilicate glasses have unique **X**-like crystals

X - needle

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

X - good/high

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

X - hydrofluoric acid

Dental Ceramics (Christy) Flashcards

(103 cards)