Most zirconia disc manufacturers work hard to ensure proper hue chroma and value of their zirconia. However, many technicians find that when they are working with the newer generation of anterior materials, their restorations are exhibiting low value results or dark zirconia.
This could be the result of this generation of cubic zirconia materials requiring more accuracy of the sintering process than any zirconia used in the past. All zirconia discs are shipped with an information for use page(user manual) in the packaging. Included on the user manual is the proper sintering cycle. For starters, it’s imperative to follow manufacturers’ instructions for sintering. Sintering zirconia too hot or holding it too long at the highest temperature will result in lowering its value or it appearing too dark.
What if you’re following the manufacturer’s user manual and still achieving the same poor results? You should check out your sintering furnace and look for factors such as:
How long has it been since you calibrated the furnace?
Did you calibrate the furnace correctly?
When sintering furnaces drift from the programmed top temperature, the temperature tends to go higher and get hotter. Hypothetically, you may have programmed top temp for 1450 degrees, but the actual result could be as much as 100 degrees higher.
If you are using the user manual for the sintering cycle and exhibiting low value gray results of any anterior zirconia like UT SHT or 3D, you should have your furnace calibrated. You could also try reducing the top temperature by 40 degrees during your next cycle. If the results are still too gray, you can try reducing the temperature by 25 degrees at a time until the value is correct. Once you have the correct value, you have likely achieved the proper sintering temperature. Please note that all zirconia becomes more opaque with lower temperature.
In case you’re interested in learning more, we have a full step-by-step guide on sintering Vsmile zirconia. Check it out here!
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