Dental Asia November/December 2022

BEHIND THE SCENES
prepare ourselves accordingly and I would
recommend the following actions:
1. Always use tools that are suitable for
zirconia finishing in the green state. I use
the Amann Girrbach Green State Finishing
Kit, it contains all the tools I need.
2. The speed specifications of the tools
should always be observed.
3. Zirconia in the green state is very
sensitive, never use too high pressure
and/or blunt tools.
4. Always keep in mind that the zirconia
shrinks by almost 20%. Due to that fact,
the surface characterisation should be
a bit deeper, but never make notches in
areas under tensile stress.
5. Use gloves and a mask and work cleanly,
milling dust must be completely removed
before sintering.
We should always should bear in mind that
although we infiltrate the zirconia with
liquids for shading, we still apply stains,
glazes and veneering ceramics later. Of
course, we want to keep the microstructure
even if these ceramic materials are applied.
We should also take this into account in
this phase, too. The microstructure we
create in the green state is later decisively
involved in the aesthetics and the natural
appearance of the restoration.
INFILTRATION
This stage has the least influence on the
final result, but it is the trickiest step. We
must improve the chroma and the effects
of the restoration without a real and
immediate visualisation of the colours we
use. The final colour becomes visible for
the first time after the sintering process.
To achieve aesthetic results, we must
understand the principle of the white and
porous zirconia foundation. I therefore
recommend to people who do not have a
lot of experience with the application of
colouring liquids to always start with tests
on blank leftovers or practice restorations,
to take photos of the last results and to
record everything you do.
If the principle is once understood, the
mental visualisation and implementation
works quite easy. For this process step, I
recommend the following preparation:
1. Prepare all the colours to be used and
follow the instructions for the materials.
2. Clean the zirconia surface with
compressed air, milling dust needs to be
fully removed.
3. Carefully start infiltration with small
brushstrokes and small amounts of liquid.
The zirconia in this stage has a high
absorption behaviour (Fig. 12).
4. Apply the chroma (dentin liquid) to the
intended areas, i.e., approximal, cervical
and occlusal. Due to the use of preshaded
zirconia, the colour only needs to
be reinforced in those areas.
5. Apply the effects e.g., in the incisal area.
SURFACE PREPARATION AND COLOUR
CUSTOMISATION
Figures 13-16 show the results after
sintering. Despite all the work, the excellent
quality of this material is evident. It is
only possible with a material like Zolid
HT+ Preshades to have such results after
sintering and to perceive the excellent
optical behaviour of zirconia. If the
restoration meets all requirements after
sintering, we can concentrate on the most
important aspect, the aesthetics.
In that case, I used the staining system
Ivocolor from Ivoclar Vivadent. This has
two reasons. The first is the wide range of
possible firing cycles, I am able to choose a
temperature between 700-890ºC without
harming its properties. The second reason
is its optical behaviour. This kit has three
unique colours on the market: Ivocolor E22,
Magenta Ivocolor E21 and Neutral Gray
Ivocolor E17. It also has three basic shades
SD0, SD1 and SD2, that form the base of
the chroma that we will need for this type
Figs. 7-8: Initial situation after milling
Fig. 9: Manual re-work of zirconia in the green state
Figs. 10-11: Final restoration after manual re-work, ready for sintering
Fig. 12: Application of the colouring liquid
DENTAL ASIA NOVEMBER/ DECEMBER 2022 45