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All Ceramic Preparations Metal-Ceramic Preparation Flashcards

1
Q

A metal-ceramic crown is also known as a

A

Porcelain Fused to Metal crown (PFM)

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2
Q

What is a metal-ceramic crown/PFM?

A

a crown that has a metal core with porcelain baked onto the metal core
- takes the strength of metal and combines it with the tooth matching esthetic ability of porcelain

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3
Q

What are the indications for using a PFM crown?

A
  • When opposing tooth is porcelain/ceramic
  • When a high level of esthetics is needed
  • When preparation is unusual
  • Bridges and other long span fixed restorations
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4
Q

What are the advantages of a PFM crown?

A
  • Natural appearance due to the porcelain baked on to the metal coping
  • More resistant to fracture than all-ceramic crowns
  • Greater strength due to metal core than all ceramic crowns
  • Design flexibility
  • Adaptable to multiple types of margin designs
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5
Q

How does a metal-ceramic/PFM crown have design flexibility?

A
  • Can have whole crown layered with porcelain.
  • Can also have metal occlusal with porcelain facing on buccal only. Metal occlusal adds strength!
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6
Q

What are the criteria for a metal-ceramic/PFM crown?

A
  • The preparations need to be designed in particular ways.
  • To accommodate metal and porcelain
  • To provide optimum strength
  • To allow for optimum esthetics
  • To decrease gingival problems associated with PFM crown design
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7
Q

What are the components of a PFM/metal-ceramic crown?

A

Porcelain:
- Opaque porcelain
- Body porcelain
- Incisal porcelain
- Shoulder porcelain
Metal:
- Minimal thickness of 0.3-0.5mm

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8
Q

Why does the porcelain of a metal-ceramic/PFM crown need to be thick?

A

to maximize esthetics

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9
Q

What is the measurement for metal-ceramic/PFM for the metal coping?

A

0.3-0.5mm in veneered areas
0.8-1.0mm in unveneered areas

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10
Q

What is the measurement for metal-ceramic/PFM for the opaque porcelain?

A

0.1-0.2mm

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11
Q

What is the measurement for metal-ceramic/PFM for the shoulder porcelain?

A

0.8mm

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12
Q

What is the measurement for metal-ceramic/PFM for the gingival, body, and incisal porcelain?

A

0.8 – 2mm

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13
Q

How much reduction is necessary for the metal occlusion of a metal-ceramic/PFM?

A

1.5mm occlusal reduction

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14
Q

How much reduction is necessary for the porcelain occlusion of a metal-ceramic/PFM?

A

2.0mm occlusal reduction

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15
Q

What is the purpose of the two-plane reduction for a metal-ceramic/PFM?

A
  • Two plane reduction allows for even thickness of material
  • Without two plane, we can possibly endanger the pulp
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16
Q

Continuing shoulder margin into and through interproximal areas before thinning to chamfer, allows for…

A

porcelain esthetics to be carried into the contact regions for maximum esthetics

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17
Q

__________ finish lines provide greater space for an esthetic thickness of metal and porcelain without having to over-contour the crown restoration

A

Shoulder

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18
Q

A proper shoulder margin with appropriate depth allows the crown margins to be contoured for…

A

optimal gingival health and esthetics

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19
Q

Why is a shoulder with a rounded line angle preferred for PFM crowns?

A
  • Easier to prepare than a sharp 90 degree angle
  • Easier to mill
  • Less stress on the tooth
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20
Q

What is a shoulder with a rounded line angle called?

A

modified shoulder margin

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21
Q

If any part of the crown is milled (metal coping), a mill cannot create a ___ degree finish line angle

A

90

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22
Q

What are the types of PFM crown margin designs?

A
  • Metal Collar
  • Disappearing Metal
  • Porcelain Margin
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23
Q

What are the characteristics of a metal collar margin for a PFM?

A
  • porcelain is stopped with some metal showing at the margin
  • Ease of fabrication and precise fit if margin cannot be large enough to accommodate metal and porcelain.
  • Also if margin is deep subgingival, metal collar allows for less material and less likely an over-contoured
  • Use heavy chamfer or shoulder
  • Margin depth 1.2mm ideally
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24
Q

What is the margin depth for a metal collar PFM crown margin design?

A

1.2 mm

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25
How can a metal collar margin design be good if the margin is deep subgingival?
allows for less material and less likely an over-contoured crown which would create gingival problems
26
What are the characteristics of a disappearing metal margin for a PFM?
– Metal is thinned to a fine line that is barely visible. - Allows for metal burnishing of margin to secure a precise fit just like Metal Collar - When margin depth is not enough to allow for porcelain and metal at the margin. - Use heavy chamfer or modified shoulder margin - Shoulder margin depth 1.0-1.2mm ideally
27
When is a disappearing metal margin on a PFM a good choice?
When margin depth is not enough to allow for porcelain and metal at the margin
28
What are the characteristics of a "porcelain margin" margin for a PFM?
– Metal and porcelain fill shoulder finish line space. No metal is seen. - Highest esthetics - Difficult to fabricate requiring excellent lab tech - Use modified shoulder margin - Shoulder margin depth 1.2mm required
29
What PFM crown margin type has the highest esthetics?
procelain margin
30
What teeth are best for the porcleain margin crown margin for PFM crown?
premolars and anteriors
31
Why are crown margins placed subgingivally?
- Esthetics - To cover dentin - When decay has extended below the gingiva - When retention / resistance is needed - Previous restorations extended sub-gingival
32
Where are subgingival margins placed?
placed 0.5mm below gingiva
33
What happens if your crown margin violates biologic width?
gingival inflammation and resorption of bone will occur
34
How far subgingival can you go before violating biologic width?
about 1.0 mm
35
What should the proper emergence profile for a PFM look like?
- Proper emergence profile creates smooth transition from tooth to crown - Extremely difficult with implant crowns
36
What is emergence profile?
- Crown and tooth contour which preserves the gingiva health
37
What is the issue with porcelain?
- Porcelain is a brittle substance that if not designed correctly can fracture - Porcelain is abrasive to natural dentition --> often see significant wear on opposing dentition
38
Porcelain needs to be less than ___ mm thick
3.0 mm
39
What happens if porcelain is not baked correctly?
porcelain will be weaker and the internal stresses of chewing etc, will likely cause fracture
40
PFM crowns do require ______ reduction of tooth structure than All Metal crowns.
more
41
However, the PFM esthetics are _______ than all metal crowns
greater
42
Fabricating PFM’s requires...
trained dental technicians who are trained in porcelain and still requires wax ups and hands on materials to fabricate.
43
The preparation design of a PFM crown is based on...
- fundamentals of tooth prep for resistance and retention - material design with metal and porcelain - esthetic requirements
44
What are the advantages of all ceramic crowns?
- ESTHETICS; Most realistic restorations we have - Can be milled - Gingival compatibility
45
What are the disadvantages of all ceramic crowns?
- Reduced strength - Substantial tooth reduction required - Technique sensitive for prep and cementation - Opposing tooth wear - Greater fracture potential - Limited use in bridges
46
What are the indications for all ceramic crowns?
- Highest level of esthetics - Light occlusal loads - Tooth preparation is possible (enough tooth remains)
47
What are the contra-indications for all ceramic crowns?
- Heavy occlusal loads - Unfavorable occlusion (Bruxer) - Short preparation with ceramic thickness greater than 3mm - Margin depth to accommodate ceramic not available
48
What is the incisal reduction for all ceramic prep?
2.0 – 2.5mm
49
What is the facial axial reduction for all ceramic prep?
1.2 – 1.7mm
50
What is the lingual axial reduction for all ceramic prep?
1.0 – 1.2mm
51
What is the marginal reduction for all ceramic prep?
1.0 – 1.2mm
52
What finish line is required for all ceramic prep?
Modified Shoulder or Heavy Chamfer required
53
What are the benefits of all ceramic crowns?
With no metal to obscure, the translucency and overall esthetics can be the best we have in dentistry
54
Why are ceramics susceptible to fracture?
- Surface flaws and Stress concentrations combine to encourage fracture - Ceramics do not have the ability to absorb the stresses on them and therefore fracture.
55
How is the brittleness overcome with All Ceramics?
- Manage occlusal forces - Restoration and Preparation design - Cement with Resin Cement - Reinforce the glass ceramics
56
What are the indications for an e.Max Lithium Disilicate?
- Anterior/Posterior single crowns - Anterior Bridge - Inlay/Onlay/Veneer
57
What is the strength of an e.Max Lithium Disilicate?
360-500 mpa enamel is 300 mpa
58
____% of the time Resin cement is required for e.Max crown
90%
59
What are the reduction requirements for an e.Max crown?
1mm margin and minimum 1.5mm reduction with ideal around 2mm reduction.
60
______ ceramics are most esthetic, so anterior use is best.
Glass
61
What conditions are unfavorable for ceramics?
Edge to Edge or occlusion in the gingival 1/5
62
Why do we use e.Max and other glass ceramics on anterior teeth?
- lower occlusal forces favoring the use of the ceramics - esthetics
63
Must have adequate tooth support for an e.Max crown as too much ceramic thickness is...
easily broken
64
All-Ceramic crowns are contra-indicated in _______
bruxers
65
Must have adequate tooth support as too much ceramic thickness is easily broken. Often not enough room on _____________ for ceramics
2nd molars
66
To help strengthen All-Ceramic crowns, ______ cement is used.
resin
67
Resin cements increase the strength of ceramic crowns by up to ____%
50%
68
_______ Cements are stronger than other conventional cements.
Resin
69
What are the preparation guidelines for all ceramic?
- Flat plane at right angle to forces - Modified shoulder or heavy chamfer - No sharp line angles - Adequate length of preparation for support - Uniform axial reduction with ideal taper
70
What should you do to the incisal edge so it isn't sharp?
round or flatten the incisal edge to reduce possible fracture
71
More than ___mm of porcelain left incisally will result in significantly higher risk of fracture
3mm
72
Excessive porcelain bulk ________ strength
decreases
73
What is the important info to know about all ceramic crowns?
- Most esthetic dental restoration to date - Prep design very important to ensure longevity and reduce fracturing - Resin cement used almost exclusively - Not for use in heavy occlusal forces - Too much ceramic weakens the restoration
74
One choice available to you for situations where an all-ceramic crown would not be preferred, is a...
PFZ - Porcelain Fused to Zirconia
75
Why are PFZ (porcelain fused to zirconia) more esthetic than PFMs?
- Full strength Zirconia to be used with an esthetic porcelain on the facial or covering the whole Zirconia core. - White core eliminates many of the esthetic problems we can have with PFMs

Fixed (13 decks)

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