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Fixed > All Ceramic Preparations Metal-Ceramic Preparation > Flashcards

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
Q

How can a metal collar margin design be good if the margin is deep subgingival?

A

allows for less material and less likely an over-contoured crown which would create gingival problems

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26
Q

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

A

– 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

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27
Q

When is a disappearing metal margin on a PFM a good choice?

A

When margin depth is not enough to allow for porcelain and metal at the margin

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28
Q

What are the characteristics of a “porcelain margin” margin for a PFM?

A

– 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

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29
Q

What PFM crown margin type has the highest esthetics?

A

procelain margin

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30
Q

What teeth are best for the porcleain margin crown margin for PFM crown?

A

premolars and anteriors

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31
Q

Why are crown margins placed subgingivally?

A
  • Esthetics
  • To cover dentin
  • When decay has extended below the gingiva
  • When retention / resistance is needed
  • Previous restorations extended sub-gingival
32
Q

Where are subgingival margins placed?

A

placed 0.5mm below gingiva

33
Q

What happens if your crown margin violates biologic width?

A

gingival inflammation and resorption of bone will occur

34
Q

How far subgingival can you go before violating biologic width?

A

about 1.0 mm

35
Q

What should the proper emergence profile for a PFM look like?

A
  • Proper emergence profile creates smooth transition from tooth to crown
  • Extremely difficult with implant crowns
36
Q

What is emergence profile?

A
  • Crown and tooth contour which preserves the gingiva health
37
Q

What is the issue with porcelain?

A
  • 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
Q

Porcelain needs to be less than ___ mm thick

A

3.0 mm

39
Q

What happens if porcelain is not baked correctly?

A

porcelain will be weaker and the internal stresses of chewing etc, will likely cause fracture

40
Q

PFM crowns do require ______ reduction of tooth structure than All Metal crowns.

A

more

41
Q

However, the PFM esthetics are _______ than all metal crowns

A

greater

42
Q

Fabricating PFM’s requires…

A

trained dental technicians who are trained in porcelain and still requires wax ups and hands on materials to fabricate.

43
Q

The preparation design of a PFM crown is based on…

A
  • fundamentals of tooth prep for resistance and retention
  • material design with metal and porcelain
  • esthetic requirements
44
Q

What are the advantages of all ceramic crowns?

A
  • ESTHETICS; Most realistic restorations we have
  • Can be milled
  • Gingival compatibility
45
Q

What are the disadvantages of all ceramic crowns?

A
  • Reduced strength
  • Substantial tooth reduction required
  • Technique sensitive for prep and cementation
  • Opposing tooth wear
  • Greater fracture potential
  • Limited use in bridges
46
Q

What are the indications for all ceramic crowns?

A
  • Highest level of esthetics
  • Light occlusal loads
  • Tooth preparation is possible (enough tooth remains)
47
Q

What are the contra-indications for all ceramic crowns?

A
  • Heavy occlusal loads
  • Unfavorable occlusion (Bruxer)
  • Short preparation with ceramic thickness greater than 3mm
  • Margin depth to accommodate ceramic not available
48
Q

What is the incisal reduction for all ceramic prep?

A

2.0 – 2.5mm

49
Q

What is the facial axial reduction for all ceramic prep?

A

1.2 – 1.7mm

50
Q

What is the lingual axial reduction for all ceramic prep?

A

1.0 – 1.2mm

51
Q

What is the marginal reduction for all ceramic prep?

A

1.0 – 1.2mm

52
Q

What finish line is required for all ceramic prep?

A

Modified Shoulder or Heavy Chamfer required

53
Q

What are the benefits of all ceramic crowns?

A

With no metal to obscure, the translucency and overall esthetics can be the best we have in dentistry

54
Q

Why are ceramics susceptible to fracture?

A
  • 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
Q

How is the brittleness overcome with All Ceramics?

A
  • Manage occlusal forces
  • Restoration and Preparation design
  • Cement with Resin Cement
  • Reinforce the glass ceramics
56
Q

What are the indications for an e.Max Lithium Disilicate?

A
  • Anterior/Posterior single crowns
  • Anterior Bridge
  • Inlay/Onlay/Veneer
57
Q

What is the strength of an e.Max Lithium Disilicate?

A

360-500 mpa

enamel is 300 mpa

58
Q

____% of the time Resin cement is required for e.Max crown

A

90%

59
Q

What are the reduction requirements for an e.Max crown?

A

1mm margin and minimum 1.5mm reduction with ideal around 2mm reduction.

60
Q

______ ceramics are most esthetic, so anterior use is best.

A

Glass

61
Q

What conditions are unfavorable for ceramics?

A

Edge to Edge or occlusion in the gingival 1/5

62
Q

Why do we use e.Max and other glass ceramics on anterior teeth?

A
  • lower occlusal forces favoring the use of the ceramics
  • esthetics
63
Q

Must have adequate tooth support for an e.Max crown as too much ceramic thickness is…

A

easily broken

64
Q

All-Ceramic crowns are contra-indicated in _______

A

bruxers

65
Q

Must have adequate tooth support as too much ceramic thickness is easily broken. Often not enough room on _____________ for ceramics

A

2nd molars

66
Q

To help strengthen All-Ceramic crowns, ______ cement is used.

A

resin

67
Q

Resin cements increase the strength of ceramic crowns by up to ____%

A

50%

68
Q

_______ Cements are stronger than other conventional cements.

A

Resin

69
Q

What are the preparation guidelines for all ceramic?

A
  • 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
Q

What should you do to the incisal edge so it isn’t sharp?

A

round or flatten the incisal edge to reduce possible fracture

71
Q

More than ___mm of porcelain left incisally will result in significantly higher risk of fracture

A

3mm

72
Q

Excessive porcelain bulk ________ strength

A

decreases

73
Q

What is the important info to know about all ceramic crowns?

A
  • 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
Q

One choice available to you for situations where an all-ceramic crown would not be preferred, is a…

A

PFZ - Porcelain Fused to Zirconia

75
Q

Why are PFZ (porcelain fused to zirconia) more esthetic than PFMs?

A
  • 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 (19 decks)

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