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Fixed Prostodontics 2 > Metal Ceramics > Flashcards

Metal Ceramics Flashcards

1
Q

Porcelain Fused to Metal (PFM) crown
consists of

A

a metal casting or coping
which fits over the prepared tooth
and has ceramic fused to the metal.

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2
Q

Porcelain Fused to Metal (PFM) crown
consists of a metal casting or coping
which fits over the prepared tooth
and has ceramic fused to the metal.

This combines

A

the strength and
accuracy of metal with the esthetics
porcelain can provide.

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3
Q

Metal Coping
(3)

A

-0.3 – 0.5mm thick with Noble metal
-0.2mm thick with Base metal
-Where Porcelain is not overlayed:
-0.8– 1.0mm thick

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4
Q

Opaquing Porcelain
—mm thick normally

A

0.2– 0.3

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5
Q

Body Porcelain
(3)

A

-done in layers
-Dentin – Enamel – Translucent – Modifiers
-0.8 – 2.0mm thick

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6
Q

High Fusing Shoulder —

A

Porcelain

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7
Q

Metal Coping
design
(3)

A

-Designed with thickness to support the
porcelain
-Design to support occlusal and proximal
contacts
-Designed with extensions to support
porcelain

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8
Q

Metal Coping
-Margin design to

A

adapt perfectly to
margins and support the porcelain if
porcelain margins are placed

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9
Q

Design of the coping
(2)

A

Convex, rounded angles
Ledge of metal to support a 90 degree Metal-
Ceramic finish

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10
Q

Assuming Metal coping is at least
0.3mm – 0.5mm thick, the metal
coping should provide:
(3)

A

-an even porcelain thickness needed to
provide optimum strength
-From 0.5 to 2mm of porcelain thickness
-Provide support in stress bearing areas
like cusp tips, incisal edges,
marginal ridges

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11
Q

A — thickness of porcelain is desirable

A

thin uniform

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12
Q

-if porcelain is more than – mm thick, a fracture of the porcelain becomes a higher risk

A

2

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13
Q

-The porcelain is supported by the rigid metal
-metal needs to be at least — mm thick for noble metals
-metal needs to be at least — mm thick for base metals

A

0.3 – 0.5
0.2

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14
Q

Ideal of — mm thick porcelain means that the metal design will vary and change
to allow for this uniform thickness

A

1 – 1.5

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15
Q

Metal Ceramic bridge designs need adequate thickness in
both the

A

pontic and connectors for rigidity to prevent
porcelain fracture while also trying to optimize esthetics.

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16
Q

Metal based Ceramics – Manufacture
Starting with a —
to create the ideal
contour and esthetics,
a — is then
designed based on
the desired porcelain
thickness. This metal is
then cast at —

A

wax up
metal coping
2300-2600 degrees or milled.

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17
Q

Once metal coping is made, porcelain is

A

“stacked”
onto coping in layers

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18
Q

Opaque porcelain

A

Masks the metal
Established the metal-ceramic bond

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19
Q

Body porcelain

A

Colors include dentin, enamel, translucent,
shoulder porcelains

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20
Q

Stains/Glazes
(3)

A

Final color match
Color modification once crown is complete
Lower fusing temp than body porcelains

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21
Q

Metal substructure
Identify the principle metals with the Identalloy system (Lab provided sticker with percent
and type of metals in the metal substructure of the crown)
(3)

A

Au-PT-Pd (Gold-Platinum-Palladium)
Pd – Ag (Gold-Palladium-Silver)
Ni-Cr-Be (Nickel-Chromium-Beryllium)

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22
Q

Metal substructure
Classified into (3)

A

High Noble, Noble, and Base metal
Each with different characteristics used in difference scenarios

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23
Q

Desirable Characteristics of Metal Ceramic Alloys
(5)

A

-Biocompatibility
-Accuracy of fit
-High Modulus of elasticity and high yield strength
-High resistance to deformation
-Easily soldered

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24
Q

High Noble Metals
Noble metal content greater than or equal to –% with at least –% of content being Gold

A

60
40

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25
Q

Gold-Platinum-Palladium
This formulation is up to as much as —% Gold
This much Gold makes this formulation —

A

88
softer and susceptible to sag

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26
Q

Gold-Palladium-Silver
The silver used to
That problem is mostly gone and overcome with new formulations

A

discolor some porcelains in a process called Greening

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27
Q

Gold-Palladium
Gold —% – Palladium —%
Resistant to sag with excellent working properties
This formulation is what we use in our PFM’s here at UMKC

A

44% - 55
35% - 45

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28
Q

Sag –

A

Resistance to deformation at high temperatures with good yield strength
and a high modulus of elasticity

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29
Q

Noble Metals
At least —% noble metals but doesn’t have to be Gold

(4)

A

25

Palladium – Silver
Palladium – Copper
Palladium – Cobalt
Palladium – Gallium

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30
Q

Noble metals are a compromise between the high noble metals and the base metals in
terms of

A

cost and in density

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31
Q

Noble Metals
The (2) can be similar to high noble

A

workability and fabrication

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32
Q

Because of less Gold, noble metals tend to have a higher — and greater —

A

strength
restistance to deformation.

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33
Q

Base Metal
(3)

A

Nickel-Chromium
Nickel-Chromium-Beryllium
Cobalt-Chromium

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34
Q

Base Metal
properties (4)

A

Stiffer metal
Harder metal
Greater Sag resistance
Lowest Density

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35
Q

Lowest Density – more difficult to

A

cast and therefore more difficult to finish in
preparation for the porcelain and not a strong solder joints

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36
Q

Lowest Density – more difficult to cast and therefore more difficult to finish in
preparation for the porcelain and not a strong solder joints
This can also lead to

A

high oxide formation and therefore problems with
bonding

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37
Q

Base Metal
Often the lowest (2)
Higher likelihood of reaction if patient has

A

cost and lowest quality of materials.
metal allergy.

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38
Q

Base Metal
Because of the Nickel and Beryllium in the base metals, two possible issues arise:

A

Allergic reaction
Toxicity

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39
Q

Allergic reaction

A

Similar to reaction to cheap jewelry due to the Nickel

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40
Q

Toxicity

A

Lab tech handling the Beryllium is at risk due to carcinogenicity

41
Q

Ceramic
PFM crowns are layered with

A

feldspathic porcelain

42
Q

feldspathic porcelain
disadvantages (2)

A

Relatively weak material
Wears opposing teeth at a very high rate

43
Q

Ceramic
properties (5)

A

Excellent Esthetic properties
Biocompatible
Excellent insulator and protection against heat and
electricity
Shrinks as its fired
Brittle

44
Q

Brittle – — strength is better than — strength

A

compressive
tensile

45
Q

Ceramic
Crack propagation –
-Porosities in the porcelain act as
-There is a stress dependent chemical reaction
between water vapor and crack tips in porcelain
that cause

A

Crack will propagate through
material until it meets something to stop it

crack initiators

growth and further fracture even with
comparatively low occlusal loading over long
periods.

46
Q

Ceramics
Predominately Glass (etchable)
(4)

A

Optical properties include most translucent
Weakest strength
Most Esthetic
Feldspathic porcelain

47
Q

Particle-filled Glass Ceramic (etchable)
(3)

A

Increased strength
Less translucent than Feldspathic
Lithium Disilicate

48
Q

Polycrystalline Ceramic (not etchable)
(3)

A

Highest strength possibilities
Lowest translucency
Zirconia

49
Q

Feldspathic Porcelain has several components
(5)

A

Feldspar
Quartz
Alumina
Glass Modifiers
Leucite

50
Q

skipped
Feldspar

A

(75% - 85%)
-Responsible for forming the glass matrix

51
Q

Quartz (silica)

A

-framework around which other components flow

52
Q

Alumina
(2)

A

-Hard strong oxide which increases strength
-Increases the viscosity of the melt when firing

53
Q

Glass Modifiers
(3)

A

-Alkali fluxes (mostly potassium and sodium oxides)
-Increases the Coefficient of Thermal Expansion
-Includes opacifiers and colorants

54
Q

Leucite

A

(10% - 20%)
-Key ingredient to increase Coefficient of Thermal Expansion to bring ceramic
closer to the Coefficient of Thermal Expansion of the metal

55
Q

Where does the strength of the PFM come from?
(3)

A

-The bond between the ceramic and the metal
substructure
-The compatibility of the metal and the porcelain
-Design and rigidity of the metal coping or framework

56
Q

Metal – Porcelain bond
The bond is accomplished with:
(4)

A

-Mechanical interlocking of materials
-Vander Waal’s forces
-Chemical bonding (at the molecular level)
-Compressive forces

57
Q

Metal – Porcelain Bond
-Mechanical Interlocking
-Microabrasions from Metal finishing or from Air Abrasion create a
surface that allows for

A

the interlocking of porcelain and metal

58
Q

-These microabrasions ….
(3)

A

also clean the surface
-These microabrasions also increase the surface area of the metal
-Finally, the microabrasions increase the “Wettability” of the metal. This means the porcelain will flow over the metal material better and therefore flow into the abraded surface

59
Q

An — layer is formed as the metal coping is
fired in the heating treatment

A

Oxide

60
Q

-An Oxide layer is formed as the metal coping is
fired in the heating treatment
-Traces of (4) move to
the surface
-Base metal alloys readily oxidize

A

Gallium, Tin, Indium, and Iron

61
Q

— are released from the metal during this
process

A

Gasses

62
Q

This oxidation stage after firing is very critical. No
—!

A

contamination

63
Q

The oxide layer of the metal bonds to similar
oxides in the opaque layer of the porcelain
-When done correctly, this oxide bond is so strong,
the porcelain will

A

break before the bond
gives away!

64
Q

Metal – Porcelain Bond
-Opaque Porcelain
-Forms oxide bond with oxide
layer of metal coping
(2)

A

-Silica oxide from Ceramic to
oxide layer of metal
-Also some Vander Waal’s
forces here

65
Q

Metal – Porcelain Bond
-Mask —
-Acts as the base for the

A

metal color
eventual shade of the crown

66
Q

Metal – Porcelain Bond
After the Opaque layer is placed:
(3)

A

Shoulder Porcelain
Body Dentin Porcelain
Enamel Porcelain

67
Q

Compatibility
-Metal Ceramic Alloys have the potential or form a

A

chemical bond using oxide layers

68
Q

-Coefficient of Thermal Expansion is matched with dental porcelain to reduce ceramic fracture in
response to

A

heating and cooling. Porcelain CTE is slightly greater than metal

69
Q

-The melting temperature of metal is considerably higher than the fusing range of the

A

veneering
dental porcelain (1600-1900 degrees)

70
Q

-The melting temperature of metal must be high enough so as to NOT

A

sag or melt when porcelain
is applied. Usually need a difference of at least 300 degrees F.

71
Q

-Higher the amount of Gold in the alloy, the lower the melting temperature
-Adding (2) raised the melting temperature
-Adding — to the alloy also raises the melting temperature

A

Platinum and Palladium
Base metals

72
Q

Because some porcelains fuse at a higher temperature than the melting temp of the metal,

A

low
fusing ceramic is used.

73
Q

Porcelain – Metal Finish line
-Anteriors
-Need adequate — overlap from facial onto the lingual
-This provides the — desired
-Metal — can cause porcelain to fracture
-Occlusion should not be on the

A

porcelain
incisal translucency
flexure
finish line
-Perferable to be at least 1.5mm away

74
Q

Porcelain – Metal Finish line
-Anteriors
-Need adequate — overlap from facial onto the lingual
-This provides the — desired
-Metal — can cause porcelain to fracture
-Occlusion should not be on the

A

porcelain
incisal translucency
flexure
finish line
-Perferable to be at least 1.5mm away

74
Q

Occlusion should not be on the

A

finish line
-Perferable to be at least 1.5mm away

74
Q

Porcelain – Metal Finish line
-Anteriors
-Need adequate — overlap from facial onto the lingual
-This provides the — desired
-Metal — can cause porcelain to fracture

A

porcelain
incisal translucency
flexure

75
Q

Porcelain – Metal Finish line
-Anteriors
Lingual porcelain on Maxillary anterior
-WILL CAUSE
-Contrainidcated in
-A lingual metal collar is desired to
-More tooth — required

A

WEAR ON OPPOSING TEETH
deep vertical overlap
support porcelain
reduction

76
Q

Advantage of a Metal lingual on Maxillary
anterior
(4)

A

-Easier to form anatomy
-Easily polished
-LESS WEAR ON OPPOSING TEETH
-Less tooth reduction required

77
Q

Porcelain – Metal Finish Line
Proximal contacts

A

-For optimum esthetics, wrap
porcelain through the contacts

78
Q

Porcelain – Metal Finish Line
-Posterior
-Occlusal surface
(3)

A

-Full Porcelain
-Full Metal
-Combination: Provides strength of full metal where needed and porcelain to
blend in buccal aspects of molars and premolars

79
Q

Porcelain – Metal Finish Line
-Posterior
-Proximal contacts
-A matter of —
-EXCEPT –
-Highly suggest all contacts are in —.

A

esthetics
A ceramic contact is much
easier to add porcelain to if a contact is
too light or is missing.

porcelain

80
Q

Porcelain – Metal Finish Line
-Posterior
-Finish line is best placed at least

A

1.5mm
away from occlusal contacts in MI, or
porcelain will tend to fracture
-Suggest for Mandibular Posteriors to either
go with full coverage porcelain veneering or
full metal occlusal to prevent fracturing of
porcelain.
-Second molars almost always get full metal
if patient can be convinced.

81
Q

Porcelain – Metal Finish Line
-Posterior
-Maxillary
-If porcelain is on the occlusal, — mm of
reduction on the occlusal is necessary
-Ideal to have — mm metal collar on the
lingual to support occlusal forces on
porcelain
-To prevent fracture, ideally to make
occlusal —

A

2
3
complete metal.

82
Q

To prevent fracture, ideally to make
occlusal complete metal.
(2)

A

-Less reduction on an already short
tooth
-Who sees that far into their mouth?

83
Q

Porcelain – Metal Finish Line
-Posterior
-Mandibular
— coverage porcelain often used for
esthetics
— mm reduction
-Metal support under lingual cusps and
marginal ridges of — mm
-If esthetic allow, a facial metal collar is
strongest, but often a thicker porcelain
margin is desired for —

A

Full
2.0
3
esthetics.

84
Q

skipped
How to decide on your Porcelain
design?
-Consider:
(5)

A

-Patients concerns for esthetics
-Clinical crown height
-Opposing occlusal surfaces
-Bruxism
-Possibly add a night guard at the end
of treatment?

85
Q

Porcelain Shoulder Margin
-Slight — placement for best esthetics
-Great margin for esthetic zones

A

subgingival

86
Q

Porcelain Shoulder Margin
-Requires special shoulder porcelain and additional technique
(4)

A

-Uses high fusing aluminous porcelain
-Need a good ceramist for this
-Need 2 additional firings at a higher temperature
-90 degree angle for strength and sealed finish line

87
Q

Metal Collar Margin
-This design is a more — tooth
preparation in cervical area
-Restoration design is easier for the lab to
fabricate
-Great for —
-Allows for —

A

conservative
molars that have margins deep
sub-gingival
multiple types of preparation finish
lines

88
Q

Disappearing Margin
(2)

A

-Indicated for areas that
the margin cannot be
hidden under the
gingiva
-Often metal copings are
over contoured and
thick at gingival area

89
Q

Bond Failure
-Cohesive Fracture is a bond failure due
to

A

traumatic incident or heavy
occlusion

90
Q

-Adhesive Fracture is the

A

de-lamination of the
porcelain from the metal

91
Q

-Adhesive Fracture is the de-lamination of the
porcelain from the metal
-This is typically a failure of the
-Contamination of

A

manufacture
process where there occurs an incorrect
oxidation process

oxide surface

92
Q

Coefficient of Thermal Expansion
(4)

A

-The CTE of metal is slightly greater than the CTE of porcelain
-If the cooling rate after firing is too rapid, the porcelain will compress too
rapidly and fracture
-A fracture will occur at this step if the porcelain is too thick or too thin
-A fracture will occur if the metal has deformed during the firing process

93
Q

— of the porcelain is the biggest drawback to the PFM crown.

A

Fracture

94
Q

Fracture of the porcelain is the biggest drawback to the PFM crown.
-Sometimes the fracture porcelain can be repaired with —
-Sometimes if the fractured portion of porcelain is intact and fits well back
together, the porcelain piece can be

A

composite

bonded back together
-This repair is reasonable, but still very weak and likely to break again

95
Q

—- is #1 reason for fracture
-The second? —-!!!

A

Poor design of the PFM (metal to porcelain)

OCCLUSION

96
Q

How to be successful with PFM crowns
-Strength comes from the bond between the —
-The type of — and metal also enhance or
detract from the bond
-Design of the metal coping for proper support of the
more fragile porcelain
-A preparation design that allows for good resistance
and retention
-Know what kind of margin you desire… High
esthetics? Bruxer?

A

metal
and ceramic
porcelain

97
Q

PFm crowns have been around for decades
and have had high degrees of success for a
long time. The metal coping protects the
tooth and the porcelain CAN be very
esthetic.
Technology continues to develop, but don’t
throw out the PFM quite yet. Its
PREDICTABILITY for bridges has yet to be
surpassed.
Next generation of this PFM concept is

A

PFZ
-Porcelain fused to Zirconia

This technology is still evolving. Early PFZ
formulations did not work. Newer
formulations are working, but the
technology is very young. You will have to
decide what to trust with your own patients.

Fixed Prostodontics 2 (13 decks)

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