Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DMS :( > ceramics > Flashcards

ceramics Flashcards

1
Q

ceramic/porcelain

A

all porcelain is ceramic but not all ceramic is porcelain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

difference between decorative and dental ceramics

A 
decorative contain kaolin
 - clay - hydrated aluminium silicate
 - opaque
dental need to be translucent so kaolin removed
 - feldspar and silica replace it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

dental ceramic constituents

A 
kaolin <5%
quartz (silica) 12-25%
feldspar 70-80%
metal oxides 1%
glass up to 15%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

decorative ceramic constituents

A 
kaolin 50+%
quartz (silica) 15-25%
feldspar 15-25%
metal oxides <1%
glass 0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

are ceramics glasses?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

feldspar

A

potash feldspar (KAl silicate)
soda feldspar (Na, Al silicate)
flux - melts and embeds other particles, increases viscosity
lowers the fusion and softening temp of the glass
lowest fusing component and flows during firing forming a solid mass around the other components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

borax

A

lowers fusing temp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

metallic oxides

A

strengtheners

colour to ceramic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

chromium

A

green

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

cobalt

A

blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

copper

A

green

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

iron

A

brown

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

manganese

A

lavender

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

nickel

A

brown

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

ceramic powder

A

dentine pink

enamel blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

conventional ceramics - making the powder

A

heat constituents to >1000 degrees
cool rapidly (fritting) in H2O - creates cracks and crazing of the ceramic mass
mill frit - fine powder
add binder - often starch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

conventional ceramics - building up the Rx

A

powder and distilled water built up
apply to die with brush
different porcelains for E and D
no further chemical reaction required - powder melts together to form crown
- crown heated in a furnace to coalesce the powder into ceramic
heating leads to sintering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what do feldspathic ceramics form when heated to 1150-1500 degrees?

A

leucite (potassium aluminium silicate)
forms around glass phase
gives powder of known physical and thermal properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

overall properties

A 
aesthetics
chemical stability
biocompatibility
thermal properties
dimensional stability
mechanical properties
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

sintering

A

occurs just above the glass transition temp
when the ceramic particles begin to fuse into a single mass
glass phase softens - coalesce
over time controlled diffusion - form solid ceramic mass
20% contraction - skilled technician to judge contraction in 3D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

chemical stability

A

v stable
generally unaffected by the wide pH range in mouth
don’t take up stain from food/drink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

biocompatibility

A

good

minimal adverse effects on biological tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

thermal properties

A 
similar to tooth
TEC similar to dentine
 - low stresses to Rx in mouth during use
thermal diffusivity low
 - protective of remaining tooth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

aesthetics

A 
best of any Rx material
colour stable
v smooth surface
retain surface better - less staining long-term
optical properties
 - reflectance
 - translucency
 - opacity
 - transparency
 - opalescence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

dimensional stability

A

once fully fired v stable
during fabrication - shrinkage - must be accommodated for by technician
- 20% normal for a conventional feldspathic ceramic crown

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

compressive strength

A

high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

hardness

A

too high

can lead to abrasion of opposing teeth esp if not glazed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

tensile strength

A

v low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

flexural strength

A

v low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

fracture toughness

A

v low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

result of mechanical properties

A

lead to failure during loading

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

static fatigue

A

cracking over time, but over v long period and less than you would get from hydrolysis of composite
time dependent decrease in strength even in the absence of any applied load
probably due to hydrolysis of Si-O group within material, over time in an aq env

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

surface microcracks

A

during manufacture, finishing or due to occlusal wear

areas where fractures can initiate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

slow crack growth

A

cyclic fatigue under occlusal forces in a wet env over time

35
Q

where can conventional ceramics be used?

A

only in low stress areas
- anterior crowns - not in all pts - if deep OB/Bruxist
too brittle for use elsewhere

36
Q

overcoming problems with conventional ceramics

A

aesthetics good but need to be stronger
produce a strong coping resistant to fracture, and cover it in conventional porcelain
cast/press a block of harder ceramic
mill a lab prepared block of ceramic

37
Q

strong coping

A

metal coping
alumina core
zirconia core

38
Q

why can alumina only be used as a core?

A

because it is opaque

39
Q

alumina core increased strength

A

flex strength double porcelain >120MPa
alumina particles act as crack stoppers - prevent propagation
- necessitates more energy to propagate a crack so more resilient

40
Q

alumina core uses

A

prev first choice for anterior crowns, not strong enough for posteriors
aesthetics could be excellent but need enough room for Al core and feldspathic layers
possibly more palatal reduction required than MCC, but less labially

41
Q

alumina core advantages

A

cheap

no specialist equipment - just need a furnace

42
Q

conventional alumina core

A

max 50% Al

43
Q

increasing the Al content and so strength

A

new techniques

  • INCERAM
  • PROCERA
44
Q

INCERAM alumina content

A

around 85%

45
Q

INCERAM flexural strength

A

high >400MPa

46
Q

In-ceram spinel

A 
has Spinel (MgAl2O4) rather than alumina as its core material
 - better aesthetics but lower flex strength
47
Q

In-ceram zirconia

A

33% zirconia replacing alumina in core

- higher strength but poorer aesthetics

48
Q

INCERAM slip casting (complicated)

A

ceramic core formed onto a refractory model
apply fine slurry of alumina
heat to 1120 degrees for 10 hours
- below glass transition temp for alumina
- partial sintering
- porous core produced
core infiltrated with lanthanum glass at 1100 degrees

49
Q

PROCERA

A

pure alumina core >99% pure

50
Q

PROCERA properties

A

high flexural strength >700MPa
possibly better translucency than glass infiltrated core
strong enough for posterior teeth, might be strong enough for bridges

51
Q

PROCERA manufacture

A

even more complicated process
core is made centrally not in every lab
a fully densified alumina core is produced at around 1700 degrees

52
Q

PROCERA and INCERAM clinical uses

A

both cores can be veneered with conventional feldspathic porcelain to produce the final crown

both probably suitable for single posterior crowns
not often used as bridge materials

53
Q

zirconia core and bonding

A

difficult to bond to

54
Q

most popular ceramic core material

A

probably zirconia

55
Q

zirconia naturally occurring mineral

A

zirconium dioxide
in different forms at diff temps
v hard

56
Q

when couldn’t zirconia be used as a core until?

A

CAD-CAM

powder doesn’t sinter unless heated >1600 degrees

57
Q

what type of zirconia should be used and why?

A

Yttria-stabilised zirconia

pure zirconia can crack on cooling

58
Q

% of yttria

A

<1%

59
Q

normal zirconia structure

A

monoclinic crystal at room temp

60
Q

Yttria structure

A

tetragonal crystal structure

61
Q

how does Yttria zirconia stabilisation work?

A

if a crack begins - when the stress at the crack tip reaches a critical level the crystal structure transforms to the monoclinic structure
causes slight expansion of material and closes crack tip
like a self-healing crack - goes from one crystal structure to a bigger crystal structure which fixes the crack

62
Q

Yttria stabilised zirconia properties

A

hard
strong (1000MPa flexural strength)
tough

strong enough to use as a bridge framework

63
Q

zirconia cored crowns fabrication

A

impression of prep - send to lab
case model then scan digitally
software unit creates a bridge substructure on virtual prep
min thickness of connectors are determined and fabricated
raw zirconia block selected for milling
pre-sintered block much easier to mill
milling for a 3 unit bridge around 1hr
cut framework heat treated 850 degrees to achieve its final physical properties
causes 20% shrinkage but computer deals with this during milling
stain
veneer it with feldspathic porcelain to produce final Rx

64
Q

manufacturers of zirconia systems

A 
LAVA from 3m
IPS e.max Zir CAD
Opalite
Zerion
Everest ZH
65
Q

problems with zirconia cored crowns

A

£££ equipment
potential for veneering porcelain to debond from core
- can inbuild stresses between the 2 materials on manufacture
opaque core - are aesthetics much better than MCC?
inert fitting surface - can’t etch or bond
- use conventional cement

66
Q

advantages of zirconia cored crowns

A

once you have the equipment they are cheaper
- cost of metal is increasing
fit generally excellent
- work at least as well as MCCs

67
Q

milled core crowns and bridges

A 
zirconia
lithium disilicate
precious metal
non-precious metal
titanium

all have a sintered surface layer for best aesthetics
- but ones milled from a single block are stronger than if you put the layer of sinter on

68
Q

milled core crowns and bridges prep

A

need to round internal angles in prep as sharp shoulder can’t be replicated in a milled Rx

69
Q

sintered vs milled

A

for the same material milled stronger than built up/pressed
- block has had ideal heat txs to maximise its properties and all blocks will be consistent

as aesthetics of ‘blocks’ of ceramic improve these will become most commonly used crown
- probably already acceptable in posterior teeth

70
Q

milled fabrication

A 
cast into scanner
scanned image of cast
lower cast is scanned and articulated
select crown margin
adjust crown margin
select crown type and place on 'model'
adjust shape and size of selected crown
save file
send to milling machine
30-40mins have crown
still requires final finishing
71
Q

truly digital workflow

A

don’t need models and impressions

  • scan in mouth
  • design on CAD machine
  • mill
  • polish
  • cement
72
Q

lithium disilicate glasses crystals

A

have unique needle-like crystals
crack propagation v difficult - good flexural strength
?maybe use for bridges

73
Q

why are cast and pressed becoming a bit redundant?

A

because of the milled ceramics

74
Q

cast and pressed ceramics technique

A

like casting a metal Rx
wax up Rx
invest
cast from a heated ingot of ceramic (1100 degrees)
no sintering - ceramic ingot is already fully condensed prior to firing
once devested and cleaned, Rx heated to improve its crystal structure producing crack inhibiting crystals - ceraming
can stain - comes out as single colour on cast
most often is cut back labially and veneered with feldspathic porcelains

75
Q

ceramic used for cast and pressed

A

glass ceramics

  • lithium disilicate glass
  • leucite reinforced glass
76
Q

ceraming

A

heat to improve its crystal structure producing crack inhibiting crystals
stage 1 - crystal formation. max no of crystal nuclei are formed
stage 2 - crystal growth to maximise physical properties
crystal phase of the ceramic can approach 100%

77
Q

strong cast and pressed ceramics

A

small crystal size and high vol fraction of crystals

78
Q

luting silica containing ceramics

A

etch with HF acid - retentive surface

  • can bond to it using a silane coupling agent
  • bond to tooth w bonding agent
79
Q

luting zirconia cored crowns

A

don’t contain silica - not affected by acid
strong enough to be self-supporting, can be luted with conventional dental cement
difficult to bond to

80
Q

lithium disilicate ceramic material advantages

A

better aesthetics than zirconia - translucency
contains silica so can etch surface to provide a reliable bond to composite luting agents, with the use of a silane coupling agent
stronger - crystalline structure

81
Q

lithium disilicate ceramic material occlusal reduction

A

min 1.5mm

82
Q

lithium disilicate ceramic material name

A

Emax

83
Q

cementing lithium disilicate ceramic material

A

silane coupling agent - give chemical bond to onlay surface
dual curing composite resin luting cement
- reduced light penetration through onlay
DBA - to allow composite resin to bond to tooth

84
Q

reinforcing ceramics

A

dispersion strengthening - alumina often used
monolithic e.g. milled from ceramic block
core (coping)

DMS :( (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions