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BDS3 DMS > dental ceramics > Flashcards

dental ceramics Flashcards

1
Q

what is the difference between decorative ceramics and dental ceramics

A

decorative - contain high kaolin and low feldspar

dental -high feldspar and glass - low kaolin

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2
Q

what property does kaolin give to ceramic

A

opacity

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3
Q

what is the function of feldspar in dental ceramics

A

lowers fusion and softening temperature of glass

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4
Q

what component of ceramic conveys colour

A

metallic oxides

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5
Q

how are conventional dental ceramics made

A

constituents heated to high temperature then cooled rapidly - fritting
frit is milled into a fine power and binder added
powder mixed with distilled water to restore

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6
Q

what is the product when feldspathic ceramics are heated 1150-1500 degrees

A

leucite (potassium aluminium silicate)

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7
Q

what is the process called when powder is coalesced into ceramic

A

sintering

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8
Q

3 properties of conventional dental ceramics

A

aesthetics - optical properties, smooth
biocompatible
chemically stable

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9
Q

normal shrinkage during firing of a conventional feldspathic crown

A

20%

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10
Q

2 positive mechanical properties of dental ceramics

A

high compressive strength

high hardness

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11
Q

3 negative mechanical properties of dental ceramic

A

low flexural strength
low fracture toughness
surface microcracks

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12
Q

where can you use feldspathic conventional ceramics in the mouth and why

A

only anterior crowns
poor mechanical properties mean can only be used in low stress areas

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13
Q

how can you make a conventional ceramic crown stronger

A

produce a strong metal coping and cover with the porcelain

alumina core - reinforce with alumina particles

zirconia core - most popular

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14
Q

how do alumina cores strengthen feldspathic porcelain

A

alumina particles act as crack stoppers and stop cracks propagating through material

opaque so only used in cores

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15
Q

heat required to sinter zirconia

A

1600 degrees Celsius

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16
Q

what type of zirconia is used in dentistry

A

yttria stabilised zirconia

17
Q

what property does yttria have on zirconia

A

gives translucency - but more yttria reduces physical properties

18
Q

what structure is zirconia before and after adding yttria

A

zirconia - monoclinic crystal

yttria - tetragonal crystal

19
Q

materials used for milled core crowns - 3

A

zirconia
precious metal - gold
non-precious metal

20
Q

once divested and cleaned, a cast and pressed ceramic crown is heated to improve its crystal structure - what is this process s called and what are produced in this process

A

ceraming

produces crack inhibiting crystals

21
Q

what are the two stages of ceraming

A

1
crystal formation - max number of crystal npc;ei formed
2
crystal growth to maximise physical properties

22
Q

what ceramics are used for cast and pressed ceramic processes

A

glass ceramics e.g. lithium disilicate glass

23
Q

why is crack propagation difficult in lithium disilicate

A

needle like crystals

24
Q

for the same material, what will be stronger a milled or built up or pressed crown

A

milled

25
Q

what material might you use for a crown of 36 and why

A

monolithic zirconia

monolithic block crowns are strongest and woill withstand masticatory forces
zirconia is stronger than LiDiSi

26
Q

what crown material would you use for a 11 crown and why

A

LiDiSi

anterior tooth so aesthetics are important factor
LiDiSi has better aesthetics as more translucent

27
Q

a pt requires an anterior bridge and has parafunction causing heavy occlusion of anterior teeth - what material would you consider

A

zirconia core with zirconia where occlusal contacts meet

28
Q

how can you make a silica containing ceramic more retentive

A

etch with hydrofluoric acid

29
Q

what do you use to bond ceramic to resin

A

silane coupling agent

30
Q

how can you make a zirconia cored crown more retentive

A

air abrasion

note non silica so unaffected by acid etch

BDS3 DMS (8 decks)

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