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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 PFM, the the metal coupling 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

0.2-0.3mm

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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 exceed 2.0 mm of body porcelain?

A

the porcelain becomes unsupported and risks fracture

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8
Q

The purpose of the 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 mm
Incisal portion: 1.1-1.2 mm
Middle/ body portion: 0.8-0.9 mm
Opaque porcelain: 0.1-0.2 mm

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

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10
Q
  1. Designed with thickness to support the porcelain
  2. designed to support occlusal and proximal contacts
  3. Designed with extensions to support porcelain
  4. Margin design to adapt perfectly to margins and support the porcelain if placed on margins
A

metal coping

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11
Q

Describe the design of the 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 need adequate thick in both the ____ and ____ 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 and esthetics, 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 is then:

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 crown is complete
  • lower fusing temp than body porcelains
A

stains/glazes

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18
Q

What does the Identalloy system provide?

A

percent and type of metals in the substructure of the 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

List the 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 is greater than or equal to 60% with atleast 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 and overcome with new 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

Atleast 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

cost & density

35
Q

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

A

less gold

36
Q

List the formations of base metals:

A

Nickel-Chromium
Nickel-Chromium-Beryllium
Cobalt-Chromium

37
Q
  • stiffer metal
  • harder metal
  • greater sag resistance
  • lowest density
  • often lowest cost
  • high likelihood of reaction/sensitivity
A

base metal

38
Q

This property of base metal makes it more difficult to cast and therefore more difficult to finish in preparation for the porcelain and 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 a stress dependent chemical reaction between the ____ & ____ that cause growth and future 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

Feldpathic porcelain

45
Q
  • particle-filled glass ceramic
  • increased strength
  • less translucent than feldspathic (but not the least)
  • etchable
A

LIthium disillicate

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 (10-20%)
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 a hard strong oxide that increases strength as well as increases the viscosity of the melt when firing

A

alumina

51
Q

Component of feldspathic porcelain:
- Alkali fluxes (mostly potassium & sodium oxides)
- increases the CTE
- includes opacifiers and colorants

A

glass modifiers

52
Q

Component of feldspathic porcelain that is the KEY INGREDIENT to increase the 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 temp changes

54
Q

Porcelains low CTE puts it at risk for:

A

fracture

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. The bond between the ceramic and the metal substructure
  2. The compatibility of the metal and the porcelain
  3. Design and rigidity of the metal comping or framework
58
Q

The metal porcelain bond in a PFM is accomplished through:

A
  1. mechanical interlocking of materials
  2. Van der Waals forces
  3. chemical bonding (at molecular level)
  4. compressive forces
59
Q

The microabrasiaion from metal finishing or air abrasion:

A
  1. clean the surface
  2. create surface that allow for interlocking of porcelain and metal
  3. increase the surface area of the metal
  4. increase wetability
60
Q

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

A

wetablility

61
Q

Which of the porcelain layers bonds to the metal coping?

A

opaque layer (the silica oxide from the porcelain to the onside layer of the metal + VDWF)

62
Q
A

Fixed Prosthodontics II (5 decks)

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