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.
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.
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
4
Q
Opaquing Porcelain
—mm thick normally
A
0.2– 0.3
5
Q
Body Porcelain
(3)
A
-done in layers
-Dentin – Enamel – Translucent – Modifiers
-0.8 – 2.0mm thick
6
Q
High Fusing Shoulder —
A
Porcelain
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
8
Q
Metal Coping
-Margin design to
A
adapt perfectly to
margins and support the porcelain if
porcelain margins are placed
9
Q
Design of the coping
(2)
A
Convex, rounded angles
Ledge of metal to support a 90 degree Metal-
Ceramic finish
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
11
Q
A — thickness of porcelain is desirable
A
thin uniform
12
Q
-if porcelain is more than – mm thick, a fracture of the porcelain becomes a higher risk
A
2
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
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
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.
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.
17
Q
Once metal coping is made, porcelain is
A
“stacked”
onto coping in layers
18
Q
Opaque porcelain
A
Masks the metal
Established the metal-ceramic bond
19
Q
Body porcelain
A
Colors include dentin, enamel, translucent,
shoulder porcelains
20
Q
Stains/Glazes
(3)
A
Final color match
Color modification once crown is complete
Lower fusing temp than body porcelains
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)
22
Q
Metal substructure
Classified into (3)
A
High Noble, Noble, and Base metal
Each with different characteristics used in difference scenarios
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
24
Q
High Noble Metals
Noble metal content greater than or equal to –% with at least –% of content being Gold
A
60
40
25
Gold-Platinum-Palladium
This formulation is up to as much as ---% Gold
This much Gold makes this formulation ---
88
softer and susceptible to sag
26
Gold-Palladium-Silver
The silver used to
That problem is mostly gone and overcome with new formulations
discolor some porcelains in a process called Greening
27
Gold-Palladium
Gold ---% -- Palladium ---%
Resistant to sag with excellent working properties
This formulation is what we use in our PFM’s here at UMKC
44% - 55
35% - 45
28
Sag –
Resistance to deformation at high temperatures with good yield strength
and a high modulus of elasticity
29
Noble Metals
At least ---% noble metals but doesn’t have to be Gold
(4)
25
Palladium – Silver
Palladium – Copper
Palladium – Cobalt
Palladium – Gallium
30
Noble metals are a compromise between the high noble metals and the base metals in
terms of
cost and in density
31
Noble Metals
The (2) can be similar to high noble
workability and fabrication
32
Because of less Gold, noble metals tend to have a higher --- and greater ---
strength
restistance to deformation.
33
Base Metal
(3)
Nickel-Chromium
Nickel-Chromium-Beryllium
Cobalt-Chromium
34
Base Metal
properties (4)
Stiffer metal
Harder metal
Greater Sag resistance
Lowest Density
35
Lowest Density – more difficult to
cast and therefore more difficult to finish in
preparation for the porcelain and not a strong solder joints
36
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
high oxide formation and therefore problems with
bonding
37
Base Metal
Often the lowest (2)
Higher likelihood of reaction if patient has
cost and lowest quality of materials.
metal allergy.
38
Base Metal
Because of the Nickel and Beryllium in the base metals, two possible issues arise:
Allergic reaction
Toxicity
39
Allergic reaction
Similar to reaction to cheap jewelry due to the Nickel
40
Toxicity
Lab tech handling the Beryllium is at risk due to carcinogenicity
41
Ceramic
PFM crowns are layered with
feldspathic porcelain
42
feldspathic porcelain
disadvantages (2)
Relatively weak material
Wears opposing teeth at a very high rate
43
Ceramic
properties (5)
Excellent Esthetic properties
Biocompatible
Excellent insulator and protection against heat and
electricity
Shrinks as its fired
Brittle
44
Brittle – --- strength is better than --- strength
compressive
tensile
45
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
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
Ceramics
Predominately Glass (etchable)
(4)
Optical properties include most translucent
Weakest strength
Most Esthetic
Feldspathic porcelain
47
Particle-filled Glass Ceramic (etchable)
(3)
Increased strength
Less translucent than Feldspathic
Lithium Disilicate
48
Polycrystalline Ceramic (not etchable)
(3)
Highest strength possibilities
Lowest translucency
Zirconia
49
Feldspathic Porcelain has several components
(5)
Feldspar
Quartz
Alumina
Glass Modifiers
Leucite
50
skipped
Feldspar
(75% - 85%)
-Responsible for forming the glass matrix
51
Quartz (silica)
-framework around which other components flow
52
Alumina
(2)
-Hard strong oxide which increases strength
-Increases the viscosity of the melt when firing
53
Glass Modifiers
(3)
-Alkali fluxes (mostly potassium and sodium oxides)
-Increases the Coefficient of Thermal Expansion
-Includes opacifiers and colorants
54
Leucite
(10% - 20%)
-Key ingredient to increase Coefficient of Thermal Expansion to bring ceramic
closer to the Coefficient of Thermal Expansion of the metal
55
Where does the strength of the PFM come from?
(3)
-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
Metal – Porcelain bond
The bond is accomplished with:
(4)
-Mechanical interlocking of materials
-Vander Waal’s forces
-Chemical bonding (at the molecular level)
-Compressive forces
57
Metal – Porcelain Bond
-Mechanical Interlocking
-Microabrasions from Metal finishing or from Air Abrasion create a
surface that allows for
the interlocking of porcelain and metal
58
-These microabrasions ....
(3)
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
An --- layer is formed as the metal coping is
fired in the heating treatment
Oxide
60
-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
Gallium, Tin, Indium, and Iron
61
--- are released from the metal during this
process
Gasses
62
This oxidation stage after firing is very critical. No
---!
contamination
63
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
break before the bond
gives away!
64
Metal – Porcelain Bond
-Opaque Porcelain
-Forms oxide bond with oxide
layer of metal coping
(2)
-Silica oxide from Ceramic to
oxide layer of metal
-Also some Vander Waal’s
forces here
65
Metal – Porcelain Bond
-Mask ---
-Acts as the base for the
metal color
eventual shade of the crown
66
Metal – Porcelain Bond
After the Opaque layer is placed:
(3)
Shoulder Porcelain
Body Dentin Porcelain
Enamel Porcelain
67
Compatibility
-Metal Ceramic Alloys have the potential or form a
chemical bond using oxide layers
68
-Coefficient of Thermal Expansion is matched with dental porcelain to reduce ceramic fracture in
response to
heating and cooling. Porcelain CTE is slightly greater than metal
69
-The melting temperature of metal is considerably higher than the fusing range of the
veneering
dental porcelain (1600-1900 degrees)
70
-The melting temperature of metal must be high enough so as to NOT
sag or melt when porcelain
is applied. Usually need a difference of at least 300 degrees F.
71
-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
Platinum and Palladium
Base metals
72
Because some porcelains fuse at a higher temperature than the melting temp of the metal,
low
fusing ceramic is used.
73
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
porcelain
incisal translucency
flexure
finish line
-Perferable to be at least 1.5mm away
74
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
porcelain
incisal translucency
flexure
finish line
-Perferable to be at least 1.5mm away
74
Occlusion should not be on the
finish line
-Perferable to be at least 1.5mm away
74
Porcelain – Metal Finish line
-Anteriors
-Need adequate --- overlap from facial onto the lingual
-This provides the --- desired
-Metal --- can cause porcelain to fracture
porcelain
incisal translucency
flexure
75
Porcelain – Metal Finish line
-Anteriors
Lingual porcelain on Maxillary anterior
-WILL CAUSE
-Contrainidcated in
-A lingual metal collar is desired to
-More tooth --- required
WEAR ON OPPOSING TEETH
deep vertical overlap
support porcelain
reduction
76
Advantage of a Metal lingual on Maxillary
anterior
(4)
-Easier to form anatomy
-Easily polished
-LESS WEAR ON OPPOSING TEETH
-Less tooth reduction required
77
Porcelain – Metal Finish Line
Proximal contacts
-For optimum esthetics, wrap
porcelain through the contacts
78
Porcelain – Metal Finish Line
-Posterior
-Occlusal surface
(3)
-Full Porcelain
-Full Metal
-Combination: Provides strength of full metal where needed and porcelain to
blend in buccal aspects of molars and premolars
79
Porcelain – Metal Finish Line
-Posterior
-Proximal contacts
-A matter of ---
-EXCEPT –
-Highly suggest all contacts are in ---.
esthetics
A ceramic contact is much
easier to add porcelain to if a contact is
too light or is missing.
porcelain
80
Porcelain – Metal Finish Line
-Posterior
-Finish line is best placed at least
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
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 ---
2
3
complete metal.
82
To prevent fracture, ideally to make
occlusal complete metal.
(2)
-Less reduction on an already short
tooth
-Who sees that far into their mouth?
83
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 ---
Full
2.0
3
esthetics.
84
skipped
How to decide on your Porcelain
design?
-Consider:
(5)
-Patients concerns for esthetics
-Clinical crown height
-Opposing occlusal surfaces
-Bruxism
-Possibly add a night guard at the end
of treatment?
85
Porcelain Shoulder Margin
-Slight --- placement for best esthetics
-Great margin for esthetic zones
subgingival
86
Porcelain Shoulder Margin
-Requires special shoulder porcelain and additional technique
(4)
-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
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 ---
conservative
molars that have margins deep
sub-gingival
multiple types of preparation finish
lines
88
Disappearing Margin
(2)
-Indicated for areas that
the margin cannot be
hidden under the
gingiva
-Often metal copings are
over contoured and
thick at gingival area
89
Bond Failure
-Cohesive Fracture is a bond failure due
to
traumatic incident or heavy
occlusion
90
-Adhesive Fracture is the
de-lamination of the
porcelain from the metal
91
-Adhesive Fracture is the de-lamination of the
porcelain from the metal
-This is typically a failure of the
-Contamination of
manufacture
process where there occurs an incorrect
oxidation process
oxide surface
92
Coefficient of Thermal Expansion
(4)
-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
--- of the porcelain is the biggest drawback to the PFM crown.
Fracture
94
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
composite
bonded back together
-This repair is reasonable, but still very weak and likely to break again
95
---- is #1 reason for fracture
-The second? ----!!!
Poor design of the PFM (metal to porcelain)
OCCLUSION
96
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?
metal
and ceramic
porcelain
97
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
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.
