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Making a framework Suitable for Margin Porcelain Application |
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Margin application increases the translucency of the cervical area
considerably. A much more natural appearance can be achieved. Also,
it may be used to make repairs on the margin area of the framework.
The preparation must be chamfer-type with a well-rounded internal angle.
Do not attempt to make a framework for a shoulder preparation; the PROCERA® scanner
cannot read a sharp internal angle. The scanner will read the corner
as if it were rounded, leaving a gap between the framework and the tooth.
If one were to put margin porcelain on such a framework, the fit will
be poor.
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Laboratory Methods for PROCERA frameworks |
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Technique I. Cutback with a diamond bur.
Use a diamond bur to reduce the margin of the framework. Use water
to avoid excess temperatures. Sandblast with 50 micron alumina at 0.3
MPa (40 psi). Caution: excess pressure, coarse diamond burs and high
speed grinding all lead to chipping and fractures.
In this case, making the PROCERA framework
is the same as in the no-margin-porcelain case.
Technique II. Scan a reduced duplicate die.
Å@Take an impression of the die and make a die stone duplicate. To make a reduced
PROCERA
framework that leaves enough space for
the margin porcelain, trim the duplicate die margin excessively to create
a new "false" margin line. (The "false" margin should be shifted radially
inward by an amount equal to the desired thickness of margin porcelain.)
Scanning the "false" margin die gives you a framework "already cut-back" for
the margin porcelain.
In this case, the Scanning Technician follows the same procedures as
in the no-margin-porcelain case.
Technique III. Make a reduced coping from a normal die by data manipulation.
Scan the normally trimmed die as usual. First choose the margin line
as usual. Then adjust the margin line in the area in which margin porcelain
is to be applied by running PREPARATIONS/SET MARGIN LINE again. In that
area, mark a new margin line that leaves enough space for the desired
thickness of margin porcelain.
Å@In this case, the responsibility for the framework reduction lies entirely
with the Scanning Technician. |
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PROCERA is a registered trademark of Nobel Biocare AB, Sweden. |
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