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Fixed Pros II > Lecture 3 - Ceramic Restorations > Flashcards

Lecture 3 - Ceramic Restorations Flashcards

1
Q

what are the applications for ceramics

A
  • all ceramic crowns
  • metal ceramic crowns
  • implant abutments and implants
  • denture teeth
  • ceramic orthodontic brackets
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2
Q

what are the benefits of ceramics

A
  • enhanced esthetics due to no metal and improved light transmission
  • looks like a tooth
  • most beneficial for teeth with normally colored dentin
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3
Q

can dentin color be shown through ceramic

A

yes

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4
Q

which materials do gingiva like

A

gold and ceramic

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5
Q

how does ceramic look like a real tooth

A
  • great color replication to produce nearly any tooth shade
  • reflect and absorb light rays stimulating enamel -refraction
  • translucency with the different types of porcelain- incisal, dentin, opaque
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6
Q

describe the flexural strength of ceramics and what is flexural strength

A
  • ceramics are brittle
  • defined as strength of a material in bending
  • stress on the outermost fibers of a bent test specimen at failure
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7
Q

what is fracture toughness

A

the resistance to fracture when crack present

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8
Q

describe the fracture toughness of metals

A

high fracture toughness due to plasticity at tip of crack, absorbs energy making crack propagation more difficult

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9
Q

describe the fracture toughness of ceramics

A

low fracture toughness
- little plasticity

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10
Q

ceramics _____ as they are fired

A

shrink

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11
Q

describe ceramics as a thermal insulator

A
  • poor conductor of heat
  • coefficient of thermal expansion is low. does not expand and contract much with heat and cold leading to fractures
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12
Q

the low fracture strength of glass ceramics is due to:

A

presence of microscopic flaws in the bulk material

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13
Q

what makes ceramics brittle

A
  • porosities in the porcelain propagate cracks
  • damage from grinding, heat propagates cracks
  • these porosities can be extended or within the material
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14
Q

why do ceramics fail at lower than expected stress

A

crack propagation

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15
Q

what will stop the crack propagation in ceramics

A

until a particle is met

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16
Q

strength of ceramics is reduced in _____ environment

A

moist

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17
Q

what is stress corrosion

A

stress- dependent chemical reaction between water vapor and crack tip causing growth and fracture with comparatively little occlusal loading

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18
Q

what are the limitations of ceramics

A
  • they are brittle
  • crack propagation
  • stress corrosion
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19
Q

what particle in ceramics make them more brittle

A

they dont have filler

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20
Q

what is the process of sintering

A

the reduction of porosities between particles as the ceramic becomes more rubbery

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21
Q

what is sintering in ceramics

A
  • ceramic powder/liquid is built up and molded (feldspathic porcelain)
  • process of heating ceramic powder once molded
  • called firing the ceramic
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22
Q

what is glass transition temperature

A
  • a range of temperature where porcelain starts to become molten
  • a transition from solid to rubbery
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23
Q

what is the numbers of glass transition temperature

A

between 540 and 610 degrees celcius

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24
Q

glass transition temperature is _____ the ceramic melting point

A

below

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25
Q

what is heat pressing and what is another name for it

A
  • relies on external pressure to sinter and shape the ceramic at high temperature
  • restoration is made from a wax pattern - lost wax technique
  • AKA high temperature injection molding
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26
Q

what does CAD/CAM stand for

A

computer aided design/ computer aided milling

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27
Q

what is hard milling

A
  • already densely sintered material
  • silicate, glass ceramics, resin based ceramics
  • burs wear out quicker and takes longer to mill
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28
Q

what is soft milling

A
  • partially sintered material
  • zirconia and lithium disilicate (emax)
  • sintering is completed in oven after manufacture
  • more common
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29
Q

what are the types of blocks available for CAD/CAM and what are the kinds of each block

A
  • glass ceramics: vita mark 2, IPS emax CAD, celtra duo ultra
  • zirconia: IPS emac ZirCAD, 3M chairside zirconia, CEREC zirconia
  • resin- ceramics: cerasmart, Vita enamic
  • Resin: telio blocks
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30
Q

what are the CAD/CAM systems available

A
  • Itero
  • Trios
  • Planmeca
    -Carestream
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31
Q

what can be done to imrprove esthetics of blocks in CAD/CAM

A

stain and glaze

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32
Q

what are the classifications of ceramics

A
  • predominately glass (veneers)
  • particle filled glass ceramic (eMax)
  • polycrystalline ceramic (zirconia)
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33
Q

describe predominately glass ceramics

A

-most translucent optical properties
- weakest material
- feldspathic porcelain
- can etch

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34
Q

describe particle filled glass ceramics (eMax)

A
  • less translucency
  • increased strength
  • lithium disilicate
  • can etch
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35
Q

describe polycrystalline ceramic (zirconia)

A
  • low translucency
  • highest strength
  • alumina, zirconia
  • cannot etch
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36
Q

how can we make ceramics stronger

A
  • resin bonding with resin cements
  • reinforcement of the crystalline structure of the ceramic
  • transformation toughening
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37
Q

describe resin bonding

A
  • can bond tooth to ceramic with the etchable ceramics
  • use of a silane coupling agent enhances bond strength
  • resin cement used- either light cure or dual cure
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38
Q

describe the reinforcement of the crystalline structure of the ceramic

A
  • dispersed crystalline phase- higher strength and fracture resistance
  • lithium disilicate
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39
Q

describe transformation toughening

A
  • stress induced transformation
  • unique to zirconia
  • compressive forces at crack tip retard crack progagation
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40
Q

how does porcelain break

A

flexure and improper loading

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41
Q

how does resin bonding add strength to ceramics

A

resin bonding is a high strength cementation procedure so bonding ceramics will decrease the ability of the ceramic to flex, therefore adding strength

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42
Q

resin bonding causes a _______ in glass ceramic crown strength

A

50% increase

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43
Q

what specific components in resin bonding cause the increased strength in ceramics

A
  • HF etched ceramic surface (retention)
  • silane coupling agent (bifunctional monomers form a chemical bond)
  • resin composite cement
  • etched enamel/ dentin - adhesive layer
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44
Q

what is the mechanism of resin bonding

A

the movement of cement into the dentin tubules microtags and into the porcelain spaces
- this forms a matrix that has good retention

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45
Q

what is the minimal thickness of porcelain in veneers

A

0.3-0.5mm

46
Q

how are tooth preps done for veneers

A

aimed at providing esthetics and physical support for the veneer

47
Q

describe veeners

A
  • not under heavy occlusal load
  • resin bonded to enamel
  • can be the most esthetic dental restoration possible
  • can be so thin, underlying tooth color can affect optical properties
  • most technically difficult to fabricate
48
Q

what does adding crystalline aspects to the ceramic do

A

crack propagation is more difficult- small cracks begin but then have a harder time causing catastrophic failure

49
Q

what is the flexural strength of feldspathic porcelain

A

60-70 MPa

50
Q

what is the flexural strength of enamel

A

300 MPa

51
Q

what is another method to strengthen porcelain

A

add a metal substructure - PFM

52
Q

what is the only material used for veneers

A

feldspathic porcelain

53
Q

what is leucite reinforced ceramic (empress) a hybrid of

A

feldspathic and eMax

54
Q

what is the flexural strength of leucite reinforced ceramic

A

120-160MPa

55
Q

would you use leucite reinforced ceramic on a posterior tooth

A
  • crown: no
  • onlay/inlay: maybe but only if occlusal forces are low
56
Q

would resin bonding strengthen leucite reinforced ceramic

A

yes because it can be etched and therefore strength and retention is increased with resin bonding

57
Q

what are the indications for leucite reinforced ceramic

A

anterior crowns and veneers

58
Q

what is the flexural strength of lithium disilicate (eMax)

A

360-500 MPa

59
Q

due to its increased strength lithium disilicate is used for:

A
  • veneers
  • anterior and posterior crowns
  • anterior bridges
  • inlays/onlays with low occlusal forces
60
Q

what cements can lithium disilicate use

A

resin bonding and RMGI

61
Q

should you use lithium disilicate ceramic for a posterior three unit bridge? why or why not

A

no because of increased fracture of material

62
Q

what is survival rate

A

remaining in place either with or without complications

63
Q

what is success rate

A

remaining unchanged and free of complications

64
Q

what are the best to worst methods of strengthening ceramics

A

zirconia > infiltration and sintering > glass ceramic > veneering porcelain

65
Q

what are the benefits of zirconia having a polycrystalline structure

A
  • increased strength
  • provides a surface that is not abrasive like porcelain but instead is gentle on opposing dentition
66
Q

does resin bonding increase the strength of zirconia

A

no

67
Q

what does resin bonding do for zirconia

A

increases retention

68
Q

what do you have to do with zirconia since it cannot be etched

A

needs the internal restoration surface to be roughened

69
Q

why cant zirconia be etched

A

contains no glass to etch

70
Q

how can you roughen the internal surface of a zirconia restoration

A
  • air abrasion
  • diamond bur
71
Q

what is needed for increased bonding of zirconia with resin cement

A

a bonding primer

72
Q

what is the flexural strength of zirconia 3Y

A

1200 MPa

73
Q

what cements can be used on 3Y zirconia

A

anything

74
Q

describe the process of making a 3Y zirconia crown

A

has to be fired and will shrink to fit- shrinks about 25% during firing

75
Q

how are zirconia crowns so strong

A

transformational toughening

76
Q

what is transforamtional toughening

A
  • stress induced transformation
  • unique to zirconia
  • compressive forces at crack tip retard crack progatation
77
Q

what happens in zirconia when a crack is initiated

A
  • tensile stress at crack tip causes tetragonal -> monoclinic shape change
  • volume increase with compressive stresses in vicinity of crack tip leading to crack closure
78
Q

what is added to make zirconia more translucent

A

yttria

79
Q

what does the addition of yttria cause

A

decreased strength

80
Q

describe 3Y zirconia

A

-100 percent tetragonal phase
- 0 percent cubic phase
- highest mechanical properties ~1200 MPa
- lowest translucency

81
Q

describe 4Y zirconia

A
  • 75% tetragonal phase
  • 25% cubic phase
  • high mechanical properties
  • higher translucency
82
Q

describe 5Y zirconia

A
  • 50% tetragonal phase
  • 50% cubic phase
  • lowest mechanical properties
  • highest translucency
83
Q

where did PFZ crowns initially have failure

A

in the posterior

84
Q

when a PFZ would fail, would the zirconia or porcelain fracture? and why

A

porcelain because of lack of porcelain support in zirconia substructure and the bond between the zirconia and the porcelain would not be able to overcome the difference in coefficient of thermal expansion between the zirconia core and the veneering porcelain

85
Q

what is the most important factor to be right if placing a PFZ in the posterior

A

occlusion!

86
Q

what is an additional benefit of PFZ crowns

A

the zirconia can help mask dark dentin- for example on an endo treated tooth

87
Q

what cement can be used with zirconia

A

any cement

88
Q

zirconia copings can be as thin as:

A

0.4mm

89
Q

a monolithic zirconia crown prep can be very conservative similar to:

A

gold or PFM crown preps

90
Q

is zirconia gentle on opposing teeth

A

yes it is considered wear friendly

91
Q

what finish lines do you use for zirconia preps

A

chamfer or should finish line

92
Q

what are the limitations of zirconia

A
  • still finding sweet spot for strength and esthetics
  • still working on bond of porcelain to zirconia
  • dont have long term data
  • still needs appropriate thickness and occlusion to survive the oral cavity
93
Q

if you want the most esthetic anterior restoration what material would you use

A
  • veneer: feldspathic porcleain
  • crown: e.max or empress
94
Q

if you want the most esthetic posterior restoration what material would you choose

A
  • crown: emax or 5Y zirconia
95
Q

if you have a bruxing patient what posterior restoration material would you use

A
  • crown: 3Y zirconia or gold
96
Q

what should you do for a bruxer/clencher who needs a bridge

A

monolithic zirconia or PFM
- possibly monolithic material with buccal porcleain

97
Q

what materials have the most to least amount of wear on opposing dentition

A

ceramics > zirconia > gold and metal

98
Q

how do you adjust glass ceramic veneers

A
  • adjust after seated and bonded with resin cement
  • use fine diamonds with a little water
  • polish with diamond impregnated polishing paste
  • internal surface should not be adjusted
99
Q

how should you adjust e.max (lithium disilicate)

A

-adjustment outside the mouth is acceptable
- fine diamond with a little water
- polish with diamond impregnated polishing paste
- internal surface should not be adjusted

100
Q

how should you adjust zirconia

A
  • adjustment outside the mouth is acceptable
  • fine diamond with a little water
  • polish with diamond impregnanted polishing paste
  • internal surface needs either air abrasion or diamond bur roughening prior to cementing
101
Q

what do you do after adjustment with bur is done

A
  • course polisher
  • fine polisher
  • felt wheel or brush with fine diamond polishing paste
102
Q

what is the surface treatment for cementing lithium disilicate

A

apply 5% HF acid for 20 seconds, rinse and dry, apply silane for 1 minute and dry

103
Q

what is the surface treatment before cementing for zirconium oxide

A

air abrasion with 50 micrometer aluminum oxiee at 7 PSI; apply an adhesion promoting agent containing MDP and dry

104
Q

resin cements require a ____ environment

A

moisture free

105
Q

resin cementes require a ____ for etched ceramics

A

silane coupling agent

106
Q

what does the primer containing MDP with resin cements do

A

placed on zirconia to enhance the chemical bond to cements containing resin

107
Q

when using RMGI cement what type of margin do you need and why

A

thick because it swells slightly

108
Q

what type of margin can you use resin cements with

A

thin margins

109
Q

when are RMGI cements contraindicated and why

A

in low strength ceramics because water absorption with setting of cement leading to slight expansion and possible fracture of ceramic at thin margin area

110
Q

are RMGI cements acceptable with zirconia

A

yes

111
Q
A

Fixed Pros II (13 decks)

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