Ivoclar Vivadent IPS d.SIGN - Manual (Page 26)

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Frameworks veneered with ceramic materials are subject to
thermal stress during the firing procedures and to
masticatory stress after cementation. Therefore, the
corresponding forces must be transferred to the framework
rather than the veneer. In particular, adequate framework
thickness must be ensured in the connector area between
the abutment and the pontic in bridge reconstructions.
The design of the framework must meet the visual,
functional and periodontal hygiene requirements of the
patient. A functional wax-up reduced to allow space for
the ceramic material is the optimum prerequisite. During the
laboratory procedures the framework is repeatedly exposed
to high temperatures. These firing temperatures may cause
the framework to distort and compromise the accuracy of fit
if it has not been properly designed and the required thickness observed. A scallop-type design with interproximal
reinforcement will provide the necessary strength needed to
avoid deformation of the framework. Also, this type of
proper framework design (e.g. with cooling grooves) will
ensure even cooling of the restoration once it is removed
from the porcelain furnace after firing. This is particularly
important if bio-alloys or high-gold alloys are used. The
corresponding failures can be prevented as described under
point 1.
In order to ensure proper oral hygiene with bridges, the
design of the interdental areas should be given special
attention. Adequate opening of the interdental area should
be considered when designing the framework without
creating black triangles. In this way, periodontal hygiene may
be performed using interdental brushes and dental floss.
4. Framework design for bridges
correct
correct
wrong