It is amazing just how many choices we are faced with when trying to select the right zirconia for your lab. It’s likely there are more different brands and types of zirconia than any product ever used in dental labs. Confusion, you bet and there are more coming. Let’s take a closer look at what’s available.
For starters, there are now three primary categories of zirconia, high strength framework material, high translucency (HT) and the newer super translucent (ST) “anterior” materials. Next are sub-categories, such as white discs with and without matching cooling systems, within each of the three categories. Additional sub-categories include pre-shaded, multi-shaded and now multi-shaded/multi-translucent discs in both the HT and ST materials. Honestly, it seems there are more brands and labels than corn fields in Nebraska. Ah, maybe not quite that many. So how does one begin the selection process?
To start, I would suggest all labs milling zirconia need a minimum of two and possibly three different materials. Most labs should be milling an HT and ST material. I use the ST for most single units and HT for most bridges. If you do a lot of layering or hybrid custom abutments I would also recommend keeping some high strength material around. That said, I would recommend working with a group of products that can be sintered in the same crucible at the same time, regardless of material category. This will improve efficiencies, reduce the number of sintering furnaces and cycles needed.
Next big decision, pre-shaded or white with green state coloring? There are tradeoffs with each decision. White discs require keeping track of each crown shade from point of CAM until it goes into the furnace. Keeping this straight requires a good system and some concentration. Using a pre-shaded disc eliminates the issues that may occur when sorting units for color as they are cut from the disc. On the other hand, doing some hand coloring on green state white zirconia will result in a more esthetic result. Keep in mind, pre-shaded discs are monochromatic. One last point on pre-shaded, you will need a much larger inventory of zirconia to maintain all the different shades and disc thicknesses.
For monolithic zirconia I believe multi-shaded and multi-shade/multi-trans will provide the most life-like end results. Keep in mind, these materials come with added inventory as they are a variation of a pre-shaded disc. In addition, you will likely need a 5-axis mill to mill multi-shaded discs. The reason being, crown STL files are positioned in the virtual disc during CAM, and are generally positioned based on path of insertion. When using a multi-shade this changes as the file needs to be placed based on shade distribution.
In conclusion, There is a lot that goes into manufacturing zirconia discs, including coloring systems, sintering furnaces and processes that go into getting a great end result. The first step in the offering of a zirconia product is disc selection and this choice will be critical to your final outcome.
Thanks for reading,
Bob Cohen, CDTBack to All Posts