FDP Framework Design Flashcards
In fixed dental prosthodontics the portion of a fixed dental prosthesis that unites the retainer and pontic
Connector
What is the function of the framework
support and marginal fit
Framework
strong or weak?
rigid or flexible?
Brittle?
Strong
Rigid
NOT brittle
Overlaying ceramics are a __ material
brittle
Function of the overlaying ceramics
Esthetics
What is the minimum required for overlaying ceramics
1mm
Overlaying ceramics need to be resistant to
compressive load
Overlaying ceramics are fragile under
tensile stress
ceramic should not exceed __ to avoid fracture
2mm
Texture of overlaying ceramics
highly polished/glazed to prevent wearing opposing dentition
Ideal wear of overlaying ceramics
10 um per year
Darker the color polishing disc the __ the grit
heavier
(blue = 1st, pink = 2nd, white = 3rd)
Framework design should be considered during the __ stage
Tx planning
Framework design should allow and even __
porcelain thickness
Framework design should have proper connector __
configuration and design
Framework design should have optimally located __
occlusal contacts
Framework design should have no abrupt contour change between
metal/porcelain
The ideal way to design framework is by waxing/ designing to ideal contours and then do an even __ of the anatomy contours desired. This way the porcelain has an even __
cutback
porcelain thickness
Metal occlusion should be used with a __ preparation
more conservative (as thin as maybe 1mm)
This provides a stronger occlusal surface (may be indicated for bruxism)
metal occlusion
Metal occlusion may be indicated when theres limited __
interocclusal clearance
Downside to metal occlusion
compromised esthetics (discuss with patient while tx planning)
With metal occlusion, what cusps should be in metal surface
Functional cusps / centric occlusion contacts
- ideally 1.5 mm away from interface
- try to avoid eccentric movement contact going over interface
Interproximal should be on either __
ONlY metal or ONLY porcelain
What is used ideally for interproximal
ideally in porcelain, it will be easier if porcelain needs to be added to close contact
Esthetics are also better
Where is plaque accumulation more common
In the interface
3 types of metal extensions/ margins
Conventional
- tooth-metal-porcelain margin interface
Metal Collar
-tooth-metal margin interface
Porcelain Butt Margin (shoulder)
- tooth-porcelain margin interface
How is light transmission different between a conventional and porcelain butt margin (shoulder)
With a conventional margin light coming in is reflected by the metal at the interface making a grey ish look to the gingiva making it less esthetic
The porcelain butt margin has enough porcelain that it reflects less light in the cervical region so its more esthetic
This provides an excellent margin seal
metal collar
This helps to preserve periodontal health
metal collar
With a metal collar, distortion of framework is __
avoided during crown fabrication
Metal collar provides __ during cementation and function
rigidity
Metal collars are usually designed with a __ to __ collar
0.5mm to 1mm
Disadvantages of metal collar
esthetics (more common on posterior teeth)
Hairline collar, disappearing margin
Conventional margin
The metal and opaque porcelain layer meet simultaneously on the preparations margin
conventional margin
What prep is recommended for conventional margin
Deep chamfer (1mm) or shoulder
- for rigidity of metal and better esthetics
Disadvantages of conventional margin
Exposed opaque porcelain layer
difficult finishing
marginal adaptation may distort after porcelain firing
This margin is commonly used on the anterior restorations
porcelain butt margin
what are the esthetic improvements with porcelain butt margin
metal elimination on margin
depth in cervical translucency
light transmission through the root
Disadvantages of porcelain butt margin
Requires a 1.2mm margin depth to achieve optimum esthetics
Difficult to obtain excellent marginal seal due to contraction of porcelain towards the greatest bulk during firing
How should the framework design be prepped
You have the freedom to design the framework design as you want, as best it fits each individual case
Agent applied to the die to provide space for the cement when cementing the restoration
Die spacer
what is the film thickness of the die spacer
25-50 um
Die spacer is applied within __ from the margin
1mm
What materials are used for the die spacer
Mostly resins are used
Model paint
Thermoplastic polymers disolved in colatile solvents
What is a cast connector
Convenient - are incorporated in the wax pattern so it minimizes the number of steps during fabrication
Disadvantage to cast connector
fit may be compromised due to distortion of the wax
What is a soldered connector
involved the use of an intermediate metal alloy with a lower melting point than the rest of the framework
with a soldered connector, the parts being joined don’t fuse but must be __ to attain a successful soldering
wetted
When is a soldered connector useful
when a framework doesn’t fit the abutments as a whole unit (FDP) but does as independent abutments (possible distortion on the connector/pontic area)
(look at steps in powerpoint to achieve this)
What is a welded connector
adjacent surfaces, the parts being connected are fused by heat or pressure
- a filler metal with a similar melting temp as the framework can be used during the procedure
What is a loop connector
sometimes are required when a diastema needs to be incorporated to a FDP
This is a weak design and is rarely used
loop connectors
where is the loop on the loop connector
Loop on the lingual aspect of the FDP
Loop connectors may be cast with the rest of the framework or shaped with a __
Pt-Au-Pd alloy wire
Connector design where one component goes inside another
Nonrigid connector (rarely used nowadays)
Mortise and tenon
Mortise = female component of non rigid connector
Tenon = male component
Path of insertion of nonrigid connector must be the same as the one of the FDP component with the
Tenon
The design of the nonrigid connectors are incorporated in the
wax pattern fabrication stage
With a nonrigid connector, paralleling usually accomplished with a
surveyor
4 indications for using a nonrigid connector
To overcome different path of insertion of abutments
Segmenting large, complex FDPs into shorter components that are easier to replace or repair
Questionable distal abutment
Relieve stresses on long FDPs
What are the rigid connectors
Cast connector
Soldered Connectors
Welded connectors
Loop connectors
What are the 3 ways the nonrigid connector can be prepared
Freehand (most difficult)
Precision machine
Prefabricated plastic patterns
A metal coping is designed to correct the path of insertion of an abutment that is tilted (usually mesially)
Telescopic crown
The coping / telescopic crown is used as a __ to fabricate the FDP
retainer
Telescopic crowns can prevent __ and even the need of __
over-preparing teeth
endodontic treatment
The Telescopic crown requires an additional __ of clearance to fit the additional metal coping
+/- 1 mm
The fabrication of a __ is always required when treating a patient for a FDP where multiple abutments will be splinted
solid cast
The solid cast should be made from the __
2nd pour of the same final impression used to fabricate the master cast (1st pour - master cast)
Should the solid cast be pin indexed and sectioned
NO
What is the reason for the solid cast
For the technician to verify the frameworks fit on a cast that has not been altered and has no removable components (master cast)
