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Fixed Prosthodontics II > L4: Metal Ceramic Restorations > Flashcards

L4: Metal Ceramic Restorations Flashcards

1
Q

What are the components of metal based ceramics?

A
  1. metal coping
  2. opaquing porcelain
  3. body porcelain
  4. high fusing shoulder porcelain
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2
Q

For a PFM the metal coping should be ____ thick when using a noble metal and ____ thick when using a base metal

A

0.3-0.5 mm

0.2 mm

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3
Q

Where porcelain is not overlayed to the metal coping, the metal should be ___ thick

A

0.8-1.0 mm

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4
Q

Opaquing porcelain is usually ____ thick

A

0.2-0.3 mm

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5
Q

Body porcelain is done in ____ and should be _____ thick

A

layers; 0.8-2.0 mm

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6
Q

List the layers of the body porcelain:

A
  1. dentin
  2. enamel
  3. translucent
  4. modifiers
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7
Q

What results when you go beyond the 2.0 mm of body porcelain?

A

The porcelain becomes unsupported and risks fracture

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8
Q

The purpose of this component of a PFM is to keep the porcelain from shrinking back, creating a gap and leading to fracture risk:

A

high fusing shoulder porcelain

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9
Q

Label the following PFM:

A

Incisal porcelain: 1.5-2.0 mm
Incisal portion:
Middle/body portion: 0.8-0.9mm
Opaque porcelain: 0.1-0.2 mm

(inside)

Cervical metal: 0.3-0.4 mm
Incisal metal: 0.2-0.3

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10
Q

-Designed with thickness to support the porcelain
-Designed to support occlusal & proximal contacts
-Designed with extensions to support porcelain
-Margin design to adapt perfectly to margins & support the porcelain if placed on margins

A

metal coping

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11
Q

Describe the design of a metal coping in a PFM:

A
  1. convex, rounded angles
  2. ledge of metal to support a 90 degree metal-ceramic finish
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12
Q

Metal ceramic bridge designs needs adequate thickness in both the ____ & ____ for rigidity to prevent porcelain fracture, while also trying to optimize esthetics

A

pontic & connectors

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13
Q

Starting with a ____ to create the ideal contour & esthetic, a metal coping is then designed based on the desired porcelain thickness. This metal is then ____ at ____ or ____

A

wax up; cast at 2300-2600 degrees or milled

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14
Q

Once the metal coping is made, the porcelain:

A

“stacked” onto coping in layers

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15
Q

Masks the metal & establishes the metal-ceramic bond:

A

opaque porcelain

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16
Q

Colors include, dentin, enamel, translucent and shoulder porcelains:

A

body porcelain

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17
Q

The final color match/modification once the crown is complete; lower fusing temp than body porcelains:

A

stains/glazes

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18
Q

What does the Identalloy system sticker provide?

A

Percent & type of metals in the metal substructure crown

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19
Q

Au-PT-Pd:

A

gold-platinum-palladium

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20
Q

Au-Pd-Ag:

A

gold-palladium-silver

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21
Q

Ni-Cr-Be:

A

nickel-chromium-beryllium

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22
Q

What are the classifications of the metals used in the metal substructure of a PFM:

A
  1. high noble
  2. noble
  3. base metal
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23
Q

Desirable characteristics of metal ceramic alloys:

A
  1. biocompatibility
  2. accuracy of fit
  3. HIGH modulus of elasticity
  4. HIGH yield strength
  5. HIGH resistance to deformation
  6. EASILY soldered
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24
Q

Noble metal content greater than or equal to 60% with at least 40% of the content being gold:

A

High noble metals

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25
Q

gold-platinum-palladium
gold-palladium-silver
gold-palladium

These are all considered:

A

high noble metals

26
Q

What happens if the metal substructure contains too much gold?

A

sag

27
Q

In gold-palladium-silver, what issue did we run into with the silver?

A

The silver used to discolor some porcelains in a process called greening. This problem is mostly gone & overcome with news formulations

28
Q

When silver discolors porcelain:

A

greening

29
Q

Benefits of gold-palladium:

What component is at a higher percentage?

A
  1. resistant to sag
  2. excellent working properties

Gold (45-55%)

30
Q

What formulation is what we use in our PFMs at UMKC?

A

Gold-palladium

31
Q

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

A

Sag

32
Q

At least 25% noble metals, but doesn’t have to be gold:

A

noble metals

33
Q

List the formulations of noble metals:

A

Palladium-silver
Palladium-copper
Palladium-cobalt
Palladium-gallium

34
Q

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

A
  1. cost
  2. density
35
Q

What aspect of noble metals tends to contribute to having higher strength & greater resistance to deformation?

A

Less gold

36
Q

List the formatulations of base metals:

A
  1. nickel-chromium
  2. nickel-chromium-beryllium
  3. cobalt-chromium
37
Q

-stiffer metal
-harder metal
-greater sag resistance
-lowest density
-often lowest cost
-high likelihood of reaction/sensitiity

A

Base meta;

38
Q

This property of base metal makes it more difficult to cast & therefore more difficult to finish in preparation for the porcelain & not able to create strong solder joints:

A

lowest density

39
Q

The lowest density property of base metal can also lead to high oxide formation and therefore problems with:

A

bonding

40
Q

With base metals, the lab tech handling the ____ is at risk due to carcinogenicity

A

Beryllium

41
Q

PFM crowns are layered with:

A

Feldspathic porcelain

42
Q

Feldspathic porcelain is brittle, meaning the _____ strength is better than the ____ strength

A

compressive; tensile

43
Q

With feldspathic porcelain on a PFM, there is stress dependent chemical reaction between ____ & ____ that cause growth & further fracture even with comparatively low occlusal loading over long periods

A

water vapor & crack tips

44
Q

-Predominately glass
-etchable
-most translucent
-weakest strength
-most esthetic

A

Feldspathic porcelain

45
Q

-particle-filled glass ceramic
-etchable
-increased strength
-less translucent than feldspathic (but not the least)

A

Lithium discilicate (e.Max & Empress)

46
Q

-polycrystalline ceramic
-not etchable
-highest strength
-lowest translucency

A

Zirconia

47
Q

Feldspathic porcelain has several components including:

A
  1. Feldspar (75-85%)
  2. Quartz (silica_
  3. Alumina
  4. Glass modifiers
  5. Leucite
48
Q

Component of feldspathic porcelain responsible for forming the glass matrix:

A

Feldspar

49
Q

Component of feldspathic porcelain creating the framework around which other components flow:

A

Quartz

50
Q

Component of feldspathic porcelain which is a hard, strong oxide that increases strength as well as increase the viscosity of the metal when firing:

A

Alumina

51
Q

Components of porcelains:

-alkali fluxes (mostly potassium & sodium oxides)
-increases coefficient of CTE
-includes opacifiers & colorants

A

Glass modifiers

52
Q

Component of feldspathic porcelain that is the KEY INGREDIENT to increase CTE to bring ceramic closer to the CTE of metal:

A

Leucite (10-20%)

53
Q

Porcelain has a low CTE meaning:

A

It doesn’t expand/contract in response to temperature changes

54
Q

Porcelains low CTE puts it at risk for:

A

fratcure

55
Q

____ increases the CTE of porcelain, making it more fracture resistant

A

leucite

56
Q

We want metal CTE to be ____ compared to the porcelain CTE

A

lower

(because if the metal expands too much under the porcelain it will cause fracture to the porcelain)

57
Q

Where does the strength of the PFM come from?

A
  1. bond between the ceramic and the metal substructure
  2. compatibility of the metal & porcelain
  3. design & rigidity of the metal coping or framework
58
Q

The metal-porcelain bond in a PFM is accomplished through:

A
  1. mechanical interlocking of materials
  2. Vander Waal’s forces
  3. chemical bonding (at molecular level)
  4. compressive forces
59
Q

The microabrasions from metal finishing or air abrasion:

A
  1. clean the surface
  2. create surface that allows for interlocking of porcelain & metal
  3. increase surface area of metal
  4. increase wearability
60
Q

Allows the porcelain to flow over the metal material better and therefore flow into the abraded surface:

A

wetability

61
Q

Which of the porcelain layers bonds to the metal coping?

A

Opaque layer

(the silica oxide from the porcelain with the oxide layer of the metal + VDWF)

62
Q
A

Fixed Prosthodontics II (15 decks)

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