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MODULE 6 > DM - ceramics > Flashcards

DM - ceramics Flashcards

1
Q

what is incorporated in dental porcelain that makes it more opaque and stronger?

A

leucite

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2
Q

how is dental porcelain customised to match dental alloys?

A

expansion/ contraction customised to match range of dental alloys - aims to have slightly higher expansion/ contraction that the underlying alloy to put porcelain in slight tangential compression

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3
Q

what are the 2 ingredients that make porcelain?

A

kaolin
feldspar

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4
Q

what does koalin do to porcelain?

A

gives tooth plasticity and allows formation of tooth structure

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5
Q

what does fledspar do to porcelain?

A

hardness and translucent appearance

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6
Q

what is added to porcelain to promote scattering of light and colouration (opalescence)?

A

particles of metal oxides

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7
Q

what does compaction do to poreclain when mixing?

A

brings particles together
patting/ vibration
blotting removes moisture

reduces firing shrinkage

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8
Q

what does firing do when mixing poreclain?

A

reduces porosity
controlled cooling to avoid cracking

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9
Q

how do you limit crack propagation in poreclain?

A

have an aluminium core (pure)
add alumina powder
sintered aluminium core
metal core - PFM

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10
Q

what are PFM alloys?

A

poreclain fused metal

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11
Q

what are the desirable properties of PFM alloys?

A

not melt when firing
rigid to support thin veneer
bond to poreclain
similar coefficient of thermal expansion to poreclain

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12
Q

what are the types of available PFM alloys?

A

high gold
low gold
silver palladium
nickel chromium

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13
Q

what technique is used to overcome shrinkage?

A

lost wax technique

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14
Q

why are filler particles added to feldspathic glasses?

A

improve mechanical properties
improve opalescence, colour and opacity

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15
Q

what filler are added to feldspathic glasses?

A

leucite (strengthening)
particles of AlO (etches at greater rate)

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16
Q

how are filler particles added to feldspathic glasses?

A

mixed in factory
grown in pressed pellet for heat treatments

17
Q

list properties of polycrystalline ceramics

A

no glassy components
atoms packed in dense arrays (inhibits crack)
relatively opaque

18
Q

how many layers are in polycrystalline ceramics?

A

6

19
Q

what are the 3 allotropes of zirconia?

A

cubic
tetragonal
monoclinic

20
Q

what are allotropic forms of carbon?

A

diamond and graphite

21
Q

list properties of ceramic

A

aesthetic
prone to crack propagation
brittle

22
Q

list properties of porcelain

A

hard
resistant to chemical attack
good thermal isulator

23
Q

how may you modify porcelain to prevent, to an extent, degree of crack propagation?

A

add glaze surface

24
Q

how can you maximise clinical durability of ceramics?

A

use max occlusal thickness
use highest elastic modulus substrate possible for core
bond the restoration
develop broad occlusal contacts

25
Q

in what case would you use conventional acid base cements?

A

zirconium oxide based ceramics

26
Q

generally, why are acid based cements not used?

A

risks etching effect that can exacerbate flaws

27
Q

how are feldspathic ceramics etched?

A

in the lab with hydrofluoric acid
or air abrasion to generate micromechanical undercut surfaces

28
Q

what is class 1a of ceramic materials?

A

monolithic ceramic for single - unit anterior prostheses, veneers, inlays, onlays adhesively cemented

29
Q

what is class 1b of ceramic materials?

A

ceramic coverage of a metal framework or a ceramic substructure

30
Q

composition of glass ceramics?

A

feldspathic porcelains
leucite - reinforced class ceramics
lithium disilicate glass ceramics

31
Q

glass-infiltrated oxide ceramics composition?

A

glass-infiltrated alumina
glass-infiltrated zirconia
glass-infiltrated spinell

32
Q

polycrystalline oxide ceramics composition?

A

aluminium oxide ceramics
zirconium dioxide ceramics

MODULE 6 (67 decks)

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