If you are outsourcing zirconia you are probably not as up on zirconia production as those that are doing this in-house. That said, let’s take an in-depth look at what is involved for an outsource facility to get you consistent quality work. Before getting into it, CAD CAM has made all of us more alike when it comes to quality. As a result, the most common problem from outsourcing facilities is achieving the correct shade. Let’s take a close look at what’s available and needed to have shades that match.
First, zirconia comes in white discs that require green state shading or coloring prior to sintering. These discs are generally the least expensive to purchase because there is no formulation of powder additives to get the desired shade. Next, there are pre-shaded discs that do match the VITA shade guide. As an example, Zirlux 16+ includes a separate disc for each 16 VITA shades plus a bleach disc. When using this material shade problems are highly unlikely. Yes, in general, pre-shaded discs do cost a little more but having every crown match is well worth it. A third disc, multi-shaded is the best of all. These are pre-shaded discs that are also layered so sintered units have a gingival, mid-body and enamel shading. This is the best material to be using. Examples of these are Katana UTML as well as Amann Girrbach Zolid FX Multilayer.
Let’s take a minute and look at just a few of the reasons white zirconia is troublesome.
When putting 20 units in a disc to mill and there are 16 different potential shades in every disc, keeping the shade correct when removing them from the disc is a challenge. Mix-ups are very easy to make as the crowns are not labeled for shade and are randomly placed in the disc.
When green state coloring units, some zirconia is subject to being more chromatic if left in the coloring solution too long.
Green state colorants all have acid in the liquids, even the water based liquids. If the facility is using sintering furnaces with MoSi2 heating elements, contaminants can cause the units to discolor during sintering.
In conclusion, I think it’s penny wise and dollar foolish to use white discs for all cases. Why introduce all the potential errors when one can easily select the right colored disc?
Thanks for reading,