Ivoclar Vivadent IPS Eris for E2 - Manual (Page 23)

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Please remember that the framework material
represents the most stable component of your
restoration and has to be given the corresponding
attention. Since the translucency of the framework material
is similar to that of natural teeth, the aesthetic appearance
will not be compromised. In large preparations, the excess in
available space must be compensated by the design of the
framework and not by the layering material.
In anterior bridges, it is not always possible to
establish a connector area of 4 x 4 mm with regard
to the linguovestibular region. In these cases, the
linguovestibular portion of the connector area may be
reduced to 3 mm, if, at the same time, the portion from the
incisal to the cervical is increased to 5–6 mm.
If only limited space is available, non-aesthetic areas (e.g.
palatal, lingual or occlusal surfaces) do not necessarily have
to be covered with layering material. In such cases, the
corresponding areas of the framework are designed in their
fully anatomical shape. The physical properties and the
abrasion values of the framework material permit users to
use this technique without reservation.
Reference guide for determining the adequate
proportion of the framework to the layering material
thickness
In order to achieve the best possible surface stability by
creating ample compressive strength, it is imperative both to
observe the working parameters and to design adequate
IPS Empress 2 frameworks. The table below clearly shows
that the fundamental objective is to make the framework
thicker than the overlaying layering material. The framework
must be as substantial as possible, with the layering material representing the aesthetic component of the restoration.
The incisal portion of natural teeth is 1.5 mm on average.
Likewise, highly aesthetic restorative results can be achieved
by applying the IPS Empress 2 framework material and
IPS Eris for E2 layering materials in a overall thickness of
1.5 mm. Keep the required ratio between the framework
and layer thickness in mind when fabricating the framework.
The following guidelines apply: The framework must be
thicker than the layer thickness of the layering material. The
minimum wall thickness of the framework is 0.8 mm. The
table below serves as a reference guide:
Ratio of framework thickness to layering material thickness
Clearance framework-layering material in mm
Layer thickness in mm
Framework thickness in mm
1.5
0.7
1.8
0.8
2.0
0.9
2.2
1.0
2.4
1.1
2.6
1.2
2.8
1.3
3.0
1.4
3.2
1.5
3.4
1.6
3.6
1.7
3.8
1.8
4.0
1.9
4.2
2.0
4.4
2.1
4.6
2.2
4.8
2.3
5.0
2.4
5.2
2.5
0.8
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
If adjustments are necessary after try-in or glaze firing, a maximum layer thickness of 2.5 mm must not be exceeded.