Soldering, Crown and Bridge, Metal Framework Bridges 
Author Message
 Soldering, Crown and Bridge, Metal Framework Bridges

      I am a crown and bridge dental laboratory owner. For many years,
I have cut and soldered metal ceramic gold alloy bridges to attain
optimum fit, adaptation, and balance to the restoration. The reasons to
do this are important, and dependant on the size, and design of the
frameworks pontics and connectors. The amount of metal in the pontic
area, (mass) has a direct effect to the amount of the metals shrinkage
after casting. The more the mass, the more the shinkage.
    This shrinkage of the metal in the raw casting can be mildly
compensated for while investing the wax-up prior to casting by
adjusting the liqiud to powder ratio of the casting investment.
However, any amount of expansion to the pontic area will also, affect
the size and adaptation of the copings to the prepared abutment teeth.
In addition, it may be guesswork at best, to determine a mass to
casting shrinkage ratio in everyday lab ops.
     What I do after I have made a casting, is cut the metal framework
diaginally through the pontic using an ultra thin cutting disk, fit the
individual abutments to the preps, and lute them together with acrylic.
I transfer this record to high heat soldering investment, and solder
it. The cut must be narrow because the size of the cut will
proportionally affect the final dimensions.
     It has been my observation over many many years, that it is
extemely rare for a metal ceramic bridge frameworks fit, that is not
sectioned after casting and repositioned on the dies, to be as good as
a cut and soldered one. A framework failure using this technique has
been extremely rare, usually being the result of a improper soldering
adaption, or, "flow"
     This cut and solder technique may be used to guarrentee a positive
seat on implant abutments where proper adaptation is extemely critical.
Take a PA of your next implant bridge. If you have a digital, or even
conventional X ray machine and the picture is taken at the correct
angle, you can see what kind of seat on the apron you really have.
     There seems to be a gray area that exists when the true results of
framework fit and adaption are "hidden by a lack of magnification"
       I am interested in the amount of strength of these "post
soldered" frameworks. It would seem that a framework that is not cut
may be a stronger by itself. However, the unacceptable integrity of
the, margins, adaptaion to the abutments, and the high possibility of a
framework "rock" are more possible without individually fit, sectioned
and soldered units.

      I am also interested in how the strength of soldered frameworks
compares to ones which have been "laser welded"
      This may not be an issue with bridges fabricated with zirconia.
However, in a practical sense, many people cannot afford zirconia based
restorations. I believe metal ceramic bridge frameworks are still going
to be around for awhile.
       Who studies the strength of these restorations? Who has the
clinical analysis? Is it just us the technicians out here in the field,
trial and error? Or is it in hard copy anywhere? Thanx, Alex

Wed, 18 Feb 2009 22:06:11 GMT
 Soldering, Crown and Bridge, Metal Framework Bridges

Good technique, my friend!


Joel344's Profile:
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Fri, 20 Feb 2009 11:21:57 GMT
 [ 2 post ] 

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