GC EUROPE Fujivest Super - Manual (Page 9)

9
Focus Edition from GC
When using the metal
casting ring technique
it is advisable to use a
high quality casting
liner such as GC New
Casting Liner. This
enables the investment
material to expand
during setting and
provide the optimal
buffer to achieve
consistently accurate castings and reduce any risk
of cracking (please see section 1.4.4).
When using the ringless technique, it is best to
use a soft type of silicone ring former to allow the
optimal setting reaction and expansion to occur.
This type of ring former also has the advantage
of being sufficiently flexible to be easily removed
from the investment material after the initial set
without the need for excessive or damaging
removal forces.
Using the more rigid type of plastic ring former
can impede the setting reaction as they tend to
be poor insulators, allowing the heat from the
exothermic reaction to be dissipated far too
quickly.
The rigidity of the plastic also means that these
formers need to be removed very quickly after the
initial set, as they allow for very little expansion.
This creates the further problem that ‘weak’
investment may be placed under too much stress
if this is done at a too early stage, resulting in
cracks or distortion.
1.4.4 Liner for metal ring types
When using a metal casting ring type, it is
advisable to use a high quality casting ring
liner such as GC New Casting Liner which is
approximately 1 mm thick. This enables the
investment material to expand during setting and
provides the optimal buffer to achieve accurate
castings and reduce the risk of cracking.