frame work design for metal ceramics Flashcards
what are the goals of framework design
even thickness of porcelain
Proper porcelain-metal interface
Good connector design
Optimally placed occlusal contacts
how can you get metal to bond to glass
glass adheres to clean, gas-free metal if covered with adherent oxide and temperature raised to where oxide is partially dissolves into the glass
why would there be an adhesive failure at porcelain metal interface
OXide layer is missing
why would there be an adhesive failure at metal oxide-metal interface
contaminated metal
why would there be an adhesive failure at porcelain-metal oxide interface
Contaminated metal oxide
how would there be a cohesive failure in porcelain
Maximum strength exceeded
why would there be a cohesive failure in metal oxide
Excesive oxidation
why would there be a cohesive failure in metal
Doesn’t happen
what does framework design determine
Occlusal contact location
where should the occlusal contact be
Opposing tooth should contact metal with 1.5mm from junction on excursive path
where should centric stop be located
1.5mm from the metal ceramic junction
why should the centric stop be located 1.5mm from the metal ceramic junction
Prevent porcelain fracture from deformation of the metal
what should you do minimize wear if vertical overlap must be minimal
Ceramic against ceramic
should metal be extended to the incisal edge
No
why shouldn’t metal be extended to the incisal edge
metal flexure or burnishing in function will cause porcelain fracture
what design should the connector have for framework design
Tresle design with it centric on porcelain
how large should connects be
Greater than 2.5 x2.5mm
what should posterior occlusion be in
MEtal or porcelain, but metal cusps should be in metal fossa
what should the proximal contacts be in
Metal or in porcelain
what is easier to add if deficient porcelain or metal
Porcelain easier to add if deficient/more esthetic on anterior
what should the proximal contact be in for posterior areas
both in metal or in porcelain
what should surround ear attachment for a parital
Surrounded by at least 1.0mm of metal to prevent flexure in function
what are the mechanical properties of porcelain
Weak in tension and strong in compression
how do you increase the compression bonding of the PFM
greater porcelain wrap around increases compression bonding and strength
how should the porcelain metal junction look
A butt joint of 90 degrees or slightly greater
where should sharp edges exist in the porcelain bearing surface
no sharp edges, all rounded in the internal and external areas of the porcelain bearing surface
how thick should the coping be
.5mm thick, or thicker to support the porcelain
what should the interproximal contact be made in
Metal or porcelain
why should marginal ridges be supported
So as to not break under compression
how large should you leave proximal ares
Enough for connectors or post soldering
whats one of the first things you should do when making an FPD
full wax-up
why should you do a full wax up
To create an incisal guide table to protect posteriors and do the lingual convity of the teeth
where should the metal be for a pfm FPD
behind the contacts
what material touches the tissue in the pontif
Porcelain
how do you make the metal good to receive porcelain in a FPD
cook at high temp to create oxide layer
what is the shit metal sometimes used for the coping
Ni-Cr
what does too much porcelain on one side of the tooth lead to
Cohesive failure
what in occlusion should you check before preping a tooth
The contact to know where to make room for contours
what design creates strength
Tressel design
