Ivoclar Vivadent Zenostar - Manual (Page 54)

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Firing parameters for Zenostar T and Zenostar MO
The following points need to be observed to achieve optimum firing results:
In order to ensure an even thickness of the veneer, the zirconium oxide restoration must be designed in such a way that it provides
support at the cusp area. Depending on the clinical situation, the consequences are different wall thicknesses and dimensions of
the framework.
Since zirconium oxide is a poor heat conductor compared to other framework materials, a low temperature increase rate is
required. This ensures even heat distribution in the bonding area between the framework and the veneer, as well as at the outer
surface of the restoration even with different framework thicknesses. In this way, an optimum bond is achieved and the layering
material is homogeneously sintered.
During cooling of the restorations after firing, stress occurs as a result of the different cooling speed at the outside and within the
material. By means of long-term cooling after the "final" firing cycle, this stress can be reduced and the risk of delamination
minimized, particularly in zirconium oxide-supported restorations.
Several objects (e.g. multi-unit bridges with massive bridge pontics) in the furnace delay even heating of the objects to be fired.
An even temperature distribution within the firing chamber depends on the type of furnace as well as the size of the firing
chamber.
The parameters stipulated in the Instructions for Use are coordinated with Ivoclar Vivadent furnaces (tolerance range ± 10°C).
If a non-Ivoclar Vivadent furnace is used, temperature corrections may be necessary.
At the beginning, open the furnace and wait for the acoustic signal. Subsequently, place the firing tray with the objects in the
centre of the firing table and start the program.
Notes on cooling after completion of the firing program
In order to ensure controlled cooling of the restoration after firing, please observe the following notes:
Wait for the acoustic signal or optical indication of the furnace at the end of the firing cycle before removing the firing tray
with the fired objects.
Do not touch hot objects with metal tongs.
Allow the objects to cool to room temperature in a place protected from draft.
Do not blast or quench the objects.