Metal & 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 & combines it with the tooth matching esthetic ability of porcelain:
PFM (metal-ceramic)
Indications for PFM include:
- when opposing tooth is:
- when a high level of ______ is needed
- When preparation is:
- ____ and other _____ fixed restorations
- porcelain or ceramic
- esthetics
- unusual
- bridges; long-span
Advantages of PFM crowns:
________ due to the porcelain baed on to 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, or it can have metal occlusal with porcelain faciing on buccal only
Design flexibility
In the case of 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 crown can adapt to?
- chamfer
- shoulder
- shoulder with bevel (not common)
To accomodate the 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?
minimal thickness of 0.3-0.5 mm
In a PFM crown porcelain thickness contributes to:
Maximizing esthetics
In PFM crown the metal coping in veneered areas= _______, while the metal coping in the unveneered areas= _____
veneered= 0.3-0.5 mm
unveneered= 0.8-1.0 mm
In a pfm crown the opaque porcelain= ______ while the shoulder porcelain= _______ while the gingival, body & incisal porcelain = ______
opaque= 0.1-0.2
shoulder= 0.8
gingival/body/incisal= 0.8-2mm
In a PFM crown, what is the metal occlusal reduction?
In a PFM crown, what is the porcelain occlusal reduction?
1.5mm
2.0mm
In a metal-ceramic crown two-plane reduction allows for:
even thickness of material
In a PFM, what does the absence of two-plane reduction possibly result in?
Endangers 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 interproximal 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 PFM crown, a proper shoulder margin with appropriate depth allows the crown margins to be contoured for:
Optimal gingival health & esthetics
Why is a shoulder with a rounded line angle preferred for PFM crowns?
- 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 finsihs
What is the shoulder referred to in PFM crowns?
modified shoulder margin
(typical shoulder creates 90 degree angle and here we are more 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 metal collar PFM crown margin design?
ease of fabrication & precise fit (if margin cannot be large enough to accomodate both metal & porcelain)
In a PRM crown preparation if margin is deep subgingival ____ allows for less material and less likely an over-contoured crown which would create gingival problems
metal collar
With a metal collar PFM crown margin design, 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 accomodate smaller
A 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 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
1.0-1.2
Type of PFM crown margin design in which metal and porcelain fill shoulder finish line space- no metal is seen:
Porcelain margin
A porcelain margin on a PFM crown allows for:
High 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 of margin design?
Modified shoulder
The modified shoulder margin depth should be _____ in a PFM crown with a porcelain margin
(this depth is REQUIRED)
1.2 mm
What type of margin design is seen in this image of PFM crowns?
Porcelain margin designs (margin slightly subgingival)
Why might crown margins be placed subgingivially?
- esthetics
- to cover dentin
- when decay has extended below the gingiva
- when retention & resistance is needed
- if previous restoration extended subgingival
In a PFM, sub-gingival margins are ideally placed:
0.5 mm below the gingiva (we think this might be the same for all crown types)
In a PFM sub-gingival margin finish lines need to be deep enough _____ to allow for adequate space for crown material
axially
When crown margin violates ______ gingival inflammation & resorption of bone will occur
biologic width
Biologic width= ________
2.0 mm
What makes up biologic width?
1.epithelial attachment
2. connective tissue
In a metal-ceramic preparation, the following described:
- crown & tooth contour which preserve 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
3 mm
If not ______ correctly, porcelain will be weaker and the internal stresses of chewing & etc. will likely cause fracture
baked
Describe porcelains effects on the natural dentition: (opposing teeth)
Porcelain is abrasive & often causes significant wear
This image here signifies:
Wear facets due to opposing porcelain
______ crowns DO require more reduction of tooth structure than all metal crowns
PFM
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 compatability
What are the disadvantages of all ceramic crowns? (6)
- describe the strength
- describe the tooth reduction
- described technique
- describe opposiing tooth wear
- describe fracture potential
- describe use
- reduced strength
- substantial tooth reduction required
- technique sensitive (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
Contra-indications for ____ crowns include
- heavy occlusal loads
- unfavorable occlusal (end to end or bruxer)
- short preparation (would make material too thick)
- not enough margin depth
all ceramic
All ceramic preparation:
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
modified should or heavy chamfer
How brittleness overcome with all ceramic crowns?
- manage occlusal forces
- restoration & preparation design
- cement with resin cement
- reinforce the glass ceramics
E. max=
Lithium disilicate (type of all ceramic material)
Ceramics do not have the ability to ____ and therefore fracture
absorb the stresses on them
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 mpa)
90% of the time, _____ is required when cementing a E. max crown
resin cement
E. max (lithium discilicate) requires _____ margin and minimum _____ reduction with ideal around _____ reduction
1 mm margin
1.5 mm
2.0 mm
What type of anterior relationships is unfavorable for E. Max & other glass ceramics:
- Edge-to-edge
- occlusion in the gingival 1/5
All ceramic crowns are contra-indicated in:
Bruxers
What tooth often does not have sufficient room for all ceramic crowns?
Second molars
To help strengthen all ceramic crowns, ____ is used & this increases the strength of these crowns by _____ %
resin cement; 50%
What type of crown follows these considerations?
-flate 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 3mm 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 & 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 to you in 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 & esthetics of porcelain
The white core of this type of crown eliminates many of the esthetic problems we have with PFMs:
PFZ
