Ivoclar Vivadent IPS e.max CAD Labside - Manual (Page 56)

Why is it important to determine the shade
of the preparation?
Depending on the translucency level of
the block used, the shade of the
preparation influences the seated all-
ceramic restoration. Therefore, knowing the shade
of the preparation is imperative. A corresponding
tooth-coloured die is then fabricated with the
help of IPS Natural Die Material. It is used to
achieve an optimum match of the restoration
shade to the given clinical situation.
When are IPS e.max CAD HT blocks used?
Given their high translucency, HT blocks are ideally
suitable for the fabrication of smaller restorations
(e.g. inlays and onlays). Restorations made of HT
blocks exhibit a true-to-nature chameleon effect
and the exceptional adaption to the remaining
tooth structure. When used for larger restorations
(e.g. crowns), the brightness level of translucent
blocks may decrease. In such cases, a block with a
lower translucency
(IPS e.max CAD LT) is required.
When are IPS e.max CAD LT blocks used?
Given their high brightness value compared to the
HT blocks, LT blocks are ideally suitable for the
fabrication of larger restorations (e.g. anterior and
posterior crowns). Restorations made of IPS e.max
CAD LT exhibit a lifelike brightness value and
chroma. This prevents the incorporated restora-
tions from graying.
Is IPS e.max CAD LT also suitable for the
fabrication of frameworks for subsequent
veneering?
The shading and translucency of the IPS e.max
CAD LT material is designed for restorations
fabricated in the staining and cut-back technique.
If frameworks are made of IPS e.max CAD LT and
subsequently fully veneered with IPS e.max Ceram
(Dentin and Incisal materials), the shade and
brightness values are slightly mismatched and the
tooth shade might differ from the shade guide.
Which type of plaster should be used to fab-
ricate the models?
The instructions for the manufacturer of the
CAD/CAM system in use should be observed in
the fabrication of the models. The following basic
rule applies: Depending on the CAD/CAM system
and equipment, special plasters may have to be
used for the fabrication of models and dies to
ensure the quality of the scan. If a special
scanning plaster is unavailable, models and dies
can be fabricated with high-strength stone, which
is sprayed with IPS Contrast Spray Labside
immediately before the scanning procedure.
What kind of preparation requirements must
the die demonstrate in order to produce
accurately fitting restorations?
The traditional preparation guidelines for all-
ceramic resotrations apply to IPS e.max CAD. The
thickness of the incisal edge of prepared anterior
teeth (upper and lower) requires special attention.
The prepared incisal edge should be at least as
thick as the diameter of the bur used in the cavity.
The corresponding instructions of the manu-
facturer regarding the dimensions of the grinding
instruments must be observed during preparation.
Can an incisal edge which has become too
thin during preparation be adjusted prior to
scanning to avoid complicating the try-in
procedure after machining?
In cases such as these, we recommend blocking
out the incisal edge of the prepared die until the
thickness matches that of the bur. These areas will
be filled with luting cement when the restoration
is seated.
How can the accuracy of fit of IPS e.max CAD
restorations be adjusted?
If the accuracy of fit on the die is to be adjusted,
this can be achieved by changing the parameters
in the corresponding CAD software. Additionally,
there is the possibility to change the dimensions
of the occlusal and proximal contacts
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e.max
® CAD
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Frequently Asked Questions
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