Metal and All-Ceramic Preparations Flashcards
A metal-ceramic crown is also known as a:
PFM
A crown that has a metal core with porcelain baked onto the metal core:
PFM (metal-ceramic)
This type of crown takes the strength of metal and combines it with the tooth matching esthetic ability of procelain:
PFM (metal-ceramic)
Indications for PFM include:
- When opposing tooth is:
- When a high level of ____ is needed
- When preparation is ____
- _____ & other ___ fixed restorations
- porcelain/ceramic
- esthetics
- unusual
- bridges; longspan
Advantages of PFM crowns:
________ due to the porcelain baked onto the metal coping
Natural appearance
Advantages of PFM crowns:
More _____ than all-ceramic crowns
resistant to fracture
Advantages of PFM crowns:
Greater ____ due to metal core than all-ceramic crowns
strength
Advantages of PFM crowns:
________- meaning it can have whole crown layered with porcelain to it can can metal occlusal with porcelain facing on buccal only.
Design flexibility
In the case of a PFM crown, metal added to the ____ adds strength
occlusal
Advantages of PFM crowns:
____ to multiple types of _____
adaptable; margin designs
What are the types of margin designs a PFM crowns can adapt to?
- chamfer
- shoulder
- shoulder with bevel (not common)
To accomodate beh requirements and benefits of using a PFM crown, the preparations need to be designed in particular ways including
- To accomodate ___
- To provide ____
- To allow for ___
- To decrease ____ associated with PFM crown design
- metal and porcelain
- optimum strength
- optimum esthetics
- gingival problems
PFM porcelain components include:
- opaque porcelain
- body porcelain
- incisal porcelain
- shoulder porcelain
What is the minimal metal thickness in a PFM crown:
0.3-0.5 mm
In a PFM crown, porcelain thickness contributes to:
maximizing esthetics
In a PFM crown the metal coping in the veneered areas = _____ while the metal coping in the unveneered areas = ____
veneered= 0.3-0.5 mm
unveneered= 0.8-1.0mm
In a PFM corn, the opaque porcelain = _____ while the shoulder porcelain = _____ while the gingival, body, and incisal porcelain = _____
opaque= 0.1-0.2 mm
shoulder= 0.8mm
gingival/body/incisal= 0.8-2.0 mm
In a PFM crown, what is the metal occlusal reduction?
In a PFM crown, what is the porcelain occlusal reduction?
1.5 mm
2.0 mm
In a metal-ceramic crown, two plane reduction allows for:
even thickness of material
In a PFM, what does the abscence of two plane reduction possibly result in?
endanger the pulp
With thinner areas in a PFM, this will decrease the ___ because it does not allow proper porcelain coverage
esthetics
In a PFM crown, what allows for porcelain esthetics to be carried into the contact regions for maximum esthetics?
continuing shoulder margin into and through the inter-proximal areas before thinning to a chamfer
In a PFM, ____ finish lines provide greater space for an esthetic thickness of metal and porcelain without having to over-contour the crown restoration
shoulder
In a PFM crown, a paper shoulder margin with appropriate depth allows the crown margins to be contoured for optimal:
gingival health and esthetics
Why is a shoulder with a rounded line angle preferred for PFM crowns? (3)
- easier to prepare than a sharp 90 degree line angle
- if crown needs to be milled, a mill cannot create a 90 degree finish line angle
- Less stress on the tooth with a rounded shoulder finish
What is the shoulder with a rounded line angle finish line referred to in PFM crowns?
modified shoulder margin (typical shoulder is 90 degrees and here we are rounded)
Type of PFM crown margin design in which the porcelain is stopped with some metal showing at the margin:
metal collar
What is the advantages to doing a metal collar PFM metal crown margin design?
Ease of fabrication & precise fit (if margin cannot be large enough to accomodate both metal and porcelain)
In a PFM crown preparation, if margin is deep subgingival, ____ allows for less material and less likely and over contoured crown which would create gingival problems:
metal collar
With a metal collar PFM crown margin, what is the design of the margin?
Heavy chamfer or shoulder (can use shoulder with bevel)
What is the margin depth when preparing a metal collar PFM crown margin design?
1.2 mm ideally but can accommodate smaller
Type of PFM crown margin design in which the metal is thinned to a fine line that is barely visible:
Disappearing metal
PFM crown margin design in which it allows for metal burnishing to secure a precise fit just like a metal collar:
disappearing metal
In a PFM crown preparation, when margin depth is not enough to allow for porcelain and metal at the margin, both a ______ and _____ are good options for the margin
metal collar & disappearing metal
What type of margin should be prepared when using a disappearing metal margin design for a PFM crown?
Heavy chamfer or modified shoulder
PFM crown margin design with disappearing metal requires a shoulder margin depth of ____ ideally but can accommodate smaller
1.0-1.2mm
Type of PFM crown margin design in which metal and porcelain fill shoulder line space. No metal is seen
Porcelain margin
A porcelain margin on a PFM crown allows for:
highest esthetics
What type of margin on a PFM crown is difficult to fabricate requiring an excellent lab tech?
Porcelain margin
A PFM with a porcelain margin uses what type of margin design?
modified shoulder
The modified shoulder margin depth should be ____ in a PFM crown with a porcelain margin (this depth is REQUIRED)
1.2mm
What type of margin design is seen in this image of PFM crowns?
porcelain margin design (margin slightly subgingival)
Why might crown margins be placed subgingivally?
- esthetics
- to cover dentin
- when decay has extended below the gingiva
- when retention & resistance is needed
- if previous restoration extended sub-gingival
In a PFM, sub-gingival margins are ideally placed:
0.5 mm below the gingiva (I think this is for all crown types)
In PFM sub-gingival margin, finish lines need to be deep enough ____ to allow for adequate space for crown material
axially
When the crown margin violates _____, gingival inflammation and resorption of bone will occur
biologic width
Biologic width =
2.0 mm
What makes up biologic width?
- epithelial attachment
- connective tissue
In a metal ceramic preparation, the following describe:
- Crown and tooth contour which conserve the gingival health
- This entity creates a smooth transition from tooth to crown
- Extremely difficult with implant crowns. One of the biggest challenges we face today with implants
Emergence profile
_____ is a brittle substance that if not designed correctly can fracture
porcelain
Porcelain needs to be less than _____ thick
3mm
If not ____ correctly, porcelain will be weaker and the internal stresses of chewing and etc., will likely cause fracture
baked
Describes porcelains effects on the natural dentition (opposing teeth)
Porcelain is abrasive to natural dentition and often causes significant wear
This image here signifies:
wear facets due to opposing porcelain
_____ crown DO require more reduction of tooth structure than all metal crowns
PFM crowns
What is the advantage of PFM crowns over all metal crowns?
esthetics
For our fixed lab in our PFM crown preparation, for the cervical finish line, the shoulder width is ____ and the lingual light chamfer is ___
shoulder width: 1.2 mm; 90 degrees
lingual light chamfer: 0.5 mm; 30-45 degrees
The MOST beautiful crowns we have:
all ceramic
What are the advantages of all ceramic crowns? (3)
- Esthetics- most realistic restorations we have
- Can be milled
- Gingival compatibility
What are the disadvantages of all ceramic crowns? (6)
- Describe the strength
- Describe the tooth reduction
- Describe technique
- Describing opposing tooth wear
- Describe fracture potential
- Describe use
- reduced strength
- substantial tooth reduction required
- technique sensitive (for prep & cementation)
- opposing tooth wear
- greater fracture potential
- limited use in bridges
Indications for a ______ crown include:
- highest level of esthetics
- light occlusal loads
- whenever enough tooth remains to allow for this prep
all ceramic
Contraindications for ____ crowns include:
- heavy occlusal loads
- unfavorable occlusion (end-to-end or bruxer)
- short preparation (would make material thickness greater than 3mm)
- Not enough margin depth
all ceramic crown
All ceramic preparation includes:
Incisal reduction =
facial axial reduction =
lingual axial reduction =
marginal reduction =
finish line type=
incisal = 2.0-2.5
facial axial= 1.2-1.7
lingual axial= 1.0-1.2
marginal = 1.0-1.2
finish line type = modified shoulder or heavy chamfer
Ceramics do not have the ability to ____ and therefore fracture
absorb the stresses on them
How is brittleness overcome with all ceramic crowns?
- manage occlusal forces
- restoration & preparation design
- cement with resin cement (bonding with resin makes it stronger)
- reinforce the glass ceramics
E. Max=
lithium discilicate (type of all ceramic material)
Indications for E. max (lithium discilicate): (3)
- anterior/posterior single crowns
- anterior bridge
- inlay/onlay/veneer
Strength of E. max (lithium discilicate) =
360-500 mpa (enamel is around 300)
90% of the time ____ is required when cementing an E. max crown
resin cement
E. max (lithium discilicate) requires ___ margin and minimum ____ reduction with ideal around ____ reduction
1mm; 1.5mm; 2mm
What type of anterior relationships are unfavorable for E. Max and other glass ceramics?
- edge-to-edge
- occlusion in the gingival 1/5
All ceramic crowns are contra-indicated in ____.
bruxers
What tooth does often not have sufficient room for all ceramic crowns?
2nd molars
To help strengthen all ceramic crowns ____ is used, and this increases the strength of these crowns by ___%
resin cement; 50%
What type of crown follows theses considerations?
- 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
all ceramic crowns
More than 3 mm of porcelain left incisally will result in:
significantly higher risk of fracture
All ceramic summary:
- Most ____ dental restoration to date
- _____ is very important to ensure longevity and reduce fracturing
- _____ is used almost exclusively
- Not for use in _____ forces
- Too much ceramic ____
- esthetic
- prep design
- resin cement
- heavy occlusal
- weakens the restoration
One choice available for situations where an all-ceramic crown would not be preferred is a ___.
PFZ- porcelain fused to zirconia
A PFZ (porcelain fused to zirconia) allows for:
strength of zirconia and esthetics of porcelain
The white core of this type of crown eliminates many of the esthetic problems we can have with PFMs:
PFZ
